key: cord-0764343-cr3drfqy
authors: Adamo, Sarah; Chevrier, Stéphane; Cervia, Carlo; Zurbuchen, Yves; Raeber, Miro E.; Yang, Liliane; Sivapatham, Sujana; Jacobs, Andrea; Baechli, Esther; Rudiger, Alain; Stüssi‐Helbling, Melina; Huber, Lars C.; Schaer, Dominik J.; Bodenmiller, Bernd; Boyman, Onur; Nilsson, Jakob
title: Profound dysregulation of T cell homeostasis and function in patients with severe COVID‐19
date: 2021-06-30
journal: Allergy
DOI: 10.1111/all.14866
sha: 613e2bcda997d7986c0e806b8faafb9ee846aae8
doc_id: 764343
cord_uid: cr3drfqy

BACKGROUND: Coronavirus disease 2019 (COVID‐19) is caused by infection with severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) and shows a broad clinical presentation ranging from asymptomatic infection to fatal disease. A very prominent feature associated with severe COVID‐19 is T cell lymphopenia. However, homeostatic and functional properties of T cells are ill‐defined in COVID‐19. METHODS: We prospectively enrolled individuals with mild and severe COVID‐19 into our multicenter cohort and performed a cross‐sectional analysis of phenotypic and functional characteristics of T cells using 40‐parameter mass cytometry, flow cytometry, targeted proteomics, and functional assays. RESULTS: Compared with mild disease, we observed strong perturbations of peripheral T cell homeostasis and function in severe COVID‐19. Individuals with severe COVID‐19 showed T cell lymphopenia and redistribution of T cell populations, including loss of naïve T cells, skewing toward CD4(+)T follicular helper cells and cytotoxic CD4(+) T cells, and expansion of activated and exhausted T cells. Extensive T cell apoptosis was particularly evident with severe disease and T cell lymphopenia, which in turn was accompanied by impaired T cell responses to several common viral antigens. Patients with severe disease showed elevated interleukin‐7 and increased T cell proliferation. Furthermore, patients sampled at late time points after symptom onset had higher T cell counts and improved antiviral T cell responses. CONCLUSION: Our study suggests that severe COVID‐19 is characterized by extensive T cell dysfunction and T cell apoptosis, which is associated with signs of homeostatic T cell proliferation and T cell recovery.

The global epidemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is the causative agent of coronavirus disease 2019 (COVID- 19) , has resulted in almost 100 million confirmed cases and 2 million deaths worldwide as of January 2021. Patients with COVID-19 have a wide spectrum of symptoms ranging from asymptomatic infection to severe acute respiratory distress syndrome (ARDS). [1] [2] [3] [4] [5] Advanced age and comorbidities are risk factors for the development of severe disease. [6] [7] [8] Furthermore, individuals with severe disease have increased amounts and longer duration of SARS-CoV-2 viral shedding in the respiratory mucosa and of viral RNA in blood as compared to individuals with mild COVID-19. [9] [10] [11] [12] Several reports have demonstrated associations between severe disease and elevation of systemic inflammatory markers such as Creactive protein (CRP), procalcitonin, and Interleukin-6 (IL-6). 6, [13] [14] [15] [16] [17] Taken together these data suggest that inefficient adaptive antiviral immunity and ensuing hyper-inflammation might underlie the pathogenesis of severe COVID-19. 18 T cells are central players in antiviral immunity. Effector T cells eliminate virus-infected cells, assist in innate antiviral response and support B cell responses, which culminate in the production of virusspecific antibodies. 12 It has been convincingly shown that severe COVID-19 is associated with reduced amounts of CD3 + T cells in peripheral blood and that the extent of T cell decrease correlates with disease severity. 10, 13, 19, 20 The reduction in peripheral T cells appears to be particularly prominent within the CD8 + T cell compartment, but it remains unclear if this is due to trafficking of CD8 + T cells into tissues with ongoing SARS-CoV-2 replication, increased elimination of CD8 + T cells during COVID-19, or pre-existing low levels of CD8 + T cells in individuals who experience severe disease.

Besides a quantitative reduction, qualitative perturbations of the T cell compartment have been observed. Several studies have reported an increased frequency of activated T cell phenotypes, 21 as well as increased expression of surface markers typical of T cell exhaustion, such as PD-1 and TIM-3. 19, 22 While a number of reports have dealt with T cell reactivity to SARS-CoV-2 proteins, [23] [24] [25] little is known about how functional responses of T cells are affected during COVID- 19. 177975, 323530-191220, and 323530-191230, respectively) and MR by a Young Talents in Clinical Research Fellowship by the Swiss Academy of Medical Sciences and the Bangerter Foundation (YTCR 32 /18) Patients with severe disease showed elevated interleukin-7 and increased T cell proliferation. Furthermore, patients sampled at late time points after symptom onset had higher T cell counts and improved antiviral T cell responses.

Our study suggests that severe COVID-19 is characterized by extensive T cell dysfunction and T cell apoptosis, which is associated with signs of homeostatic T cell proliferation and T cell recovery.

COVID-19, lymphopenia, SARS-CoV-2, T cells

In severe COVID-19 T cell populations show perturbations, including loss of naïve T cells, CD4 + T cell skewing toward T follicular helper and cytotoxic phenotypes and expansion of activated and exhausted T cells. Apoptosis and migration contribute to the lymphopenia of severe disease, which is accompanied by Interleukin-7 elevation. Functional responses to viral antigens are reduced in severe COVID-19.

To provide a detailed investigation of the peripheral T cell compartment, we performed mass cytometry, flow cytometry, targeted proteomics, and functional assays to phenotypically and functionally characterize the changes associated with symptomatic and relate them to disease severity. We observed peripheral T cell loss in both naïve and memory populations, especially among CD8 + F I G U R E 1 Characteristics of COVID-19 patients and healthy subjects included in the cross-sectional study. (A) Number of subjects recruited into the study (left) and time since onset of symptoms at sampling (right). (B) Age distribution of controls and of patients grouped by disease severity subcategories. (C) Gender distribution of healthy subjects, patients with mild disease, and patients with severe disease. (D) t-SNE plots of normalized marker expression for up to 1,000 T cells from each sample analyzed by mass cytometry. Regions with high expression of specific markers appear red. (E) t-SNE plot of the T cells of our study colored by disease severity. Areas occupied prevalently by events corresponding to patients can be visualized on the marker specific t-SNE plots to derive the phenotypes This was accompanied by increased T cell apoptosis, perturbations of the T cell   compartment, and impaired T cell responses toward other viral an- tigens. Furthermore, we observed stronger T cell responses in patients sampled at later time points after onset of symptoms, which, together with the increased Interleukin-7 (IL-7) serum concentrations and evidence of substantial T cell proliferation, suggests a role for lymphopenia-induced proliferation in severe COVID-19.

To characterize the immune response associated with SARS-CoV-2 infection we conducted a prospective, observational, and crosssectional study on symptomatic COVID-19 patients recruited at hospitals in the Canton of Zurich, Switzerland. The included patients were stratified based on clinical disease severity at the time of sampling (mild, n = 54; severe, n = 49); a group of healthy controls was included for comparison (n = 27) ( Figure 1A ). Patients were sampled at a single time point during their symptomatic phase ( Figure 1A ).

Standard laboratory parameters and clinical characteristics of the included patients are presented in Table 1 . In agreement with previous studies, 21, 22 we observed that patient age was positively correlated with disease severity ( Figure 1B ) and that males were overrepresented in the severe COVID-19 subgroup ( Figure 1C ).

We performed a comprehensive T cell characterization making use of a mass cytometry panel (Table S1 and Figure S1A -C) in a subset of patients (mild, n = 28; severe, n = 38, healthy, n = 22). These data are available at http://dx.doi.org/10.17632/ s84vd 72fsz.1. T cell-related markers were visualized on t-distributed Stochastic Neighbor Embedding (t-SNE) maps focusing on a subset of T cells from each sample, as identified based on a random forest classification ( Figure 1D , Figure S1D ). 26 By assessing the distribution of events on separate t-SNE maps for healthy controls, patients with mild disease and patients with severe disease, we observed differences between healthy donors and COVID-19 patients ( Figure 1E ).

Notably, cells from healthy individuals showed accumulation in an area of the t-SNE map enriched for CD45RA, whereas events from patients were more represented in areas enriched for CD45RO, CD57, and Granzyme B ( Figure 1D -E).

We determined the frequencies of naïve, central memory, effector memory, and terminal effector memory expressing CD45RA (TEMRA) CD4 + and CD8 + T cell subsets by manual gating among all T cells in COVID-19 patients and controls (Figure 2A ,B, top panels).

The frequency of the subsets within CD4 + or CD8 + cells is shown in stacked bar plots for individual patients (Figure 2A ,B, bottom panels). As previously reported, 21 patients with severe disease had decreased frequencies of naïve cells within the CD4 + and CD8 + T cell compartments compared to controls (Figure 2A-D) . At the same time, the percentages of central memory CD4 + and CD8 + T cells were increased in severe COVID-19 ( Figure 2C ,D).

In order to investigate how the relative changes observed within the different T cell subsets related to absolute cell counts, we performed flow cytometry of whole blood. By measuring absolute cell counts for CD4 + and CD8 + T cells we could calculate absolute numbers for the different T cell subpopulations within our mass cytometry data set ( Figure S2A ). The marked reduction in naïve CD4 + and CD8 + T cells was confirmed by absolute counts and was especially pronounced for naïve CD8 + T cells ( Figure 2C ,D). In contrast, central memory and effector memory populations within the CD4 + T cell compartment also showed a reduction in COVID-19 patients compared to healthy controls ( Figure 2C ).

Absolute numbers of central memory CD8 + T cells, effector memory CD8 + T cells, and TEMRA CD8 + T cells were also reduced in patients with severe disease compared to controls ( Figure 2D ). Thus, in severe COVID-19, naïve T cell reduction was not accompanied by memory T cell expansion but rather by a slight decrease of the memory compartment, especially among CD8 + T cells. The impression of a relative increase in memory (especially central memory) populations was mainly created by the predominant reduction in naïve cells in the peripheral blood. Of note, the T cell reduction in peripheral blood was accompanied by strong T cell activation across all the main subsets ( Figure S2B ).

Patients with severe COVID-19 in our cohort were older than patients with mild disease ( Figure 1B) , which could account for some differences in the distribution of T cell populations as previously proposed. 27 Generally, both lymphopenia and naïve T cell reduction correlated with age ( Figure S3A ). Since age and clinical severity are strongly linked, some of the alterations within the T cell compartment might be due to immunological aging. Upon stratification of patients according to age, we still detected differences between mild and severe COVID-19 patients in terms of total and naïve T cells, although the CD8 + T cell reduction in patients above 60 years of age was not statistically significant ( Figure S3B ). The same was true when we stratified individuals according to gender ( Figure S3C ).

In our healthy control group, we saw a correlation between age and CD8 + T cell decline ( Figure S4A ) while this was not the case for CD4 + cells. Conversely, CD4 + T cells were reduced in male individuals compared to females ( Figure S4B ).

We next investigated how the distribution of CD4 + T cell subpopulations ( Figure S5A ) was altered during COVID-19. We saw a significant increase in T follicular helper cells and T regulatory cells, as well as terminally differentiated, activated, and exhausted T cells ( Figure 3A ). Interestingly, a population of Granzyme B + terminally differentiated (CD28 − ) cells, compatible with cytotoxic CD4 + T cells, that was absent in healthy controls was strongly increased in COVID-19. This population likely corresponds to the one identified at the transcriptional level by others. 28 cell counts were reduced. T regulatory cells were strongly altered in terms of frequency but not in absolute counts ( Figure 3B ), perhaps reflecting a shift in the global distribution of CD4 + T cell subsets rather than T regulatory cell proliferation. Expansion of CD4 + T cells with a cytotoxic phenotype, terminally differentiated and exhausted cells was also confirmed by absolute counts ( Figure 3B ).

In order to visualize the most prominent changes within the CD4 + compartment we calculated the fold change of absolute counts for the described T cell populations between mild and severe COVID-19

as well as healthy controls ( Figure 3C ). Indeed, we observed that the most prominent changes in patients with severe COVID-19 compared to healthy controls was the increase in cytotoxic CD4 + T cells, as well as the increase in terminally differentiated and exhausted cells. We next analyzed populations within the CD8 + compartment ( Figure S5B ) and observed an increase of activated and exhausted CD8 + T cells in terms of frequency ( Figure 3D ) and absolute counts ( Figure 3E ). CD8 + T cells with a cytotoxic phenotype (Granzyme B + , CD28 − ) were increased in percentage but not in absolute number ( Figure 3D -F). Among CD8 + cells, the most prominent change observed was the increase in exhausted T cells, which also showed a strong difference between mild and severe patients ( Figure 3F ).

PhenoGraph unsupervised clustering of T cell populations revealed a similar picture ( Figure S7A -B).

We next investigated apoptosis and cell migration as possible mechanisms contributing to peripheral T cell loss in patients with severe COVID-19. Several factors can contribute to T cell apoptosis 

Note: Mann-Whitney-Wilcoxon test was used to test for differences between continuous variables adjusted for multiple testing using the Holm method. * Indicates significance (p-value threshold <.05) compared to the healthy, ** in the severe indicates significance in comparison to the healthy and the mild. Categorical variables were compared using Chi-square test, * indicates significance (p-value threshold <.05) overall.

Abbreviations: ARDS, acute respiratory distress syndrome; ICU, intensive care unit; IQR, interquartile range; LDH, Lactate Dehydrogenase. a COVID-19 disease severity at the time of blood sample collection. Mild illness and pneumonia are considered mild COVID-19 disease and severe pneumonia as well as any grade of ARDS are considered severe COVID-19 disease. b COVID-19 grade according to WHO guidelines, recorded at sampling and prospectively followed until recovery.

c Glucocorticoids initiated as part of the COVID-19 treatment.

in severe COVID-19 including cytokine signaling, direct interaction of the virus with T cells via CD26 or CD147 and elevated plasma Fas ligand levels as described for SARS-CoV. 29, 30 Excessive pro-inflammatory cytokine signaling, especially mediated by TNFα, can directly lead to T cell apoptosis. 31 As TNFα levels were considerably elevated in our cohort ( Figure S8A ) in agreement TEMRA CD8 + T cells ( Figure 4A ). Among CD8 + T cells, the extent of apoptosis was greater in samples from patients with severe as compared to mild COVID-19 ( Figure 4A ). Even within the group with mild disease, the extent of T cell apoptosis was strongly associated with symptom severity in the CD8 subset as shown by increased apoptosis in patients with mild pneumonia ( Figure 4B ). Increased T cell apoptosis could thus contribute to the lymphopenia that is a hallmark of severe COVID-19.

T cell reduction in peripheral blood can also be a consequence of T cell migration to tissues and lymphocyte accumulation in the lungs during COVID-19 has been reported by some 33, 34 but not by others. 35, 36 We therefore looked for indirect signs of T cell migration in the peripheral blood of COVID-19 patients. T cell migration into inflamed lung parenchyma is primarily mediated by CXCR3 signaling, 37,38 so we investigated the level of CXCR3 ligands in the serum of COVID-19 patients. CXCR3 ligands CXCL9, CXCL10, and CXCL11

were significantly increased in sera from COVID-19 patients, especially in sera from patients with severe disease ( Figure 4C ).

Furthermore, IFNγ, a potent inducer of CXCR3 ligands, 39 was markedly elevated ( Figure 4C and Figure S8B ). We also observed a very strong reduction in CXCR3 expression in all the main T cell subsets with the exception of naïve CD4 + T cells in COVID-19 patients ( Figure 4D and Figure S8C ). Reduced CXCR3 expression on MAIT cells and CD8 + T cells has previously been reported, 40 whereas reduced CXCR3 levels on memory CD4 + populations have been associated with a negative prognosis. 41 CXCR3 abundance inversely correlated with levels of CXCL9, CXCL10, CXCL11, and IFNγ, and was positively correlated with CD3 + , CD4 + , and CD8 + T cell frequencies ( Figure 4E ). The frequency of apoptosis in CD4 + and CD8 + T cell populations also seemed to inversely correlate with absolute T cell numbers ( Figure 4E ). Taken together, our data suggest that both migration and apoptosis might contribute to T cell lymphopenia.

We next investigated whether the observed changes within the but not for stimulation with mitogens or super-antigens ( Figure 5B and Figure S9A ). Taken together, these data suggest that antiviral T cell responses are impaired in patients with severe COVID-19 and that these responses tend to improve in patients sampled at later time points from symptom onset.

Reduced blast formation upon stimulation with specific viral antigens is likely mediated by a combination of factors, but reduced frequency of virus-specific memory T cells is likely to play a central role.

In support of this, we found that blast formation positively correlated with absolute peripheral CD4 + and CD8 + T cell counts ( Figure S9B ,C).

We therefore hypothesized that the improvement of T cell function for CD8 + T cells ( Figure 5C ). To explore whether T cell reconstitution was a potential mechanism, we investigated T cell proliferation in the different T cell populations. We could indeed observe increased frequencies of proliferating (Ki-67 + ) in multiple subsets of CD4 + and CD8 + T cells in COVID-19 patients, especially in patients with severe disease ( Figure 5D and Figure S10A-B) .

Given the extent of the lymphopenia in severe COVID-19 we hypothesized that lymphopenia-induced proliferation might play a role. IL-7 is known to be a critical homeostatic factor for T cells, and since IL-7 production by stromal cells is relatively constant, 44,45 IL-7 serum levels are mainly regulated by its consumption by lymphocytes. In patients with severe disease, we observed higher serum IL-7 levels compared to those with mild disease and healthy controls ( Figure 5E ), in agreement with a previous report. 46 Furthermore, IL-7 levels inversely correlated with the total number of CD3 + , CD4 + and CD8 + T cells ( Figure 5F ). Taken together, these findings suggest that the lymphopenia in severe COVID-19 could result in a systemic IL-7 elevation, which in turn might contribute to the observed T cell proliferation. The occurrence of peripheral lymphopenia has been described in several human acute respiratory viral infections. 47, 48 In severe COVID-19, the extent of lymphopenia is closely linked to disease severity and mortality. 32 Since disease severity in COVID-19 is strongly associated with biological age, age-associated decline in lymphocyte counts could in part account for the observed lymphopenia. A recent study, which showed a strong correlation between T cell lymphopenia, diminished SARS-CoV-2-specific T cell responses and severe disease also suggested an association between age and decline in the fraction of naïve CD8 + T cells. 18 Investigating the effect of age in our patient cohort poses a challenge, as this is strongly linked to disease severity. In our healthy control group, however, we saw a correlation between age and CD8 + T cell decline, while this was not the case for CD4 + cells. Despite association with disease severity and male gender, we did not observe CD8 + T cell reduction when comparing males to females among healthy controls, but saw a modest reduction of CD4 + T cells. Given the limited number of subjects, these data must be interpreted with caution, but it is conceivable that age and gender account for pre-existing alterations of the T cell compartment that influence the course of COVID-19 disease.

Within the T cell compartments, we saw a prevalent reduction of naïve T cells, which resulted in increased memory subsets percentages despite the slight contraction in absolute numbers. Whether the loss of naïve populations can be explained by the acquisition of a memory phenotype by virus specific cells or in an antigen independent way remains to be seen.

Another potential explanation for the loss of naïve cells might be selective or preferential death of these subsets. In this study we observed extensive T cell apoptosis in COVID-19, especially among CD8 + T cells, suggesting that apoptosis could be a central mechanism in the immunopathology of severe COVID-19. Apoptosis could be caused by the inflammatory microenvironment generated by SARS-CoV-2, although a direct interaction of the virus with T cells via CD147 or CD26 or perhaps even T cell infection cannot be excluded. In our study, we could not identify a temporal component to the increased apoptosis, but we observed signs of T cell recovery starting at day 20, suggesting that apoptosis might occur relatively early in the disease course.

Lymphocyte redistribution, that is, migration to inflamed tissues, can also be a cause of apparent peripheral lymphopenia. In our study, we found elevated amounts of CXCL9, CXCL10, and When investigating the T cell function in COVID-19, we found reduced T cell responses to several viral antigens in severe disease.

The most likely explanation for this finding is a reduction in the precursor frequency of memory cells specific for common antigens. A similar effect has recently been described for B cells in measles, 53, 54 where it has been linked to direct B cell infection and cell death. In 

For quantification of the main T cell subsets, blood samples were processed in the accredited routine immunology laboratory at University Hospital Zurich. Flow cytometry staining, assessment and analysis was done as established, 58,59 using the reagents and methodology detailed in the Appendix S1.

Samples were pre-processed as described in the Appendix S1

and mass cytometry analysis was performed as previously described. 17,60-67 A detailed description of the procedure is provided in the Appendix S1. 

Serum was collected in BD vacutainer clot activator tubes (Becton Dickinson). The samples were processed in an accredited immunology laboratory at the Department of Immunology of University Hospital Zurich. IFNγ and TNFα were quantified using an ELISA (R&D Systems), as previously established. 68

Heat-inactivated plasma samples were analyzed using the Olink® Proteomics 92-plex inflammation immunoassay. A brief description of the method is provided in the Appendix S1. 

We thank Alessandra Guaita, Jennifer Jörger, Sara Hasler, the members of the transplantation immunology laboratory, and the members of the Boyman laboratory for their support of the study. We thank Natalie de Souza for helpful discussions. The graphical abstract was created with BioRender.com. 

Presymptomatic SARS-CoV-2 infections and transmission in a skilled nursing facility

Potential presymptomatic transmission of SARS-CoV-2

Substantial undocumented infection facilitates the rapid dissemination of novel coronavirus (SARS-CoV-2)

Characteristics of and important lessons from the coronavirus disease 2019 (COVID-19) outbreak in China: summary of a report of 72314 cases from the Chinese center for disease control and prevention

Clinical course and outcomes of critically ill patients with SARS-CoV-2 pneumonia in Wuhan, China: a singlecentered, retrospective, observational study

Clinical course and risk factors for mortality of adult inpatients with COVID-19 in Wuhan, China: a retrospective cohort study

Risk factors for severe and critically ill COVID-19 patients: a review

Immunology of COVID-19: Mechanisms, clinical outcome, diagnostics, and perspectives-A report of the European academy of allergy and clinical immunology (EAACI)

Viral dynamics in mild and severe cases of COVID-19

Impaired type I interferon activity and exacerbated inflammatory responses in severe Covid-19 patients

Viral and host factors related to the clinical outcome of COVID-19

Systemic and mucosal antibody responses specific to SARS-CoV-2 during mild versus severe COVID-19

COVID-19 with different severities: a multicenter study of clinical features

Clinical predictors of mortality due to COVID-19 based on an analysis of data of 150 patients from Wuhan, China

Risk factors associated with acute respiratory distress syndrome and death in patients with coronavirus disease 2019 pneumonia in Wuhan, China

Clinical, radiological, and laboratory characteristics and risk factors for severity and mortality of 289 hospitalized COVID-19 patients. Allergy Eur

A distinct innate immune signature marks progression from mild to severe COVID-19

Antigen-specific adaptive immunity to SARS-CoV-2 in acute COVID-19 and associations with age and disease severity

Reduction and functional exhaustion of t cells in patients with coronavirus disease 2019 (COVID-19)

Predictors of mortality for patients with COVID-19 pneumonia caused by SARSCoV-2: a prospective cohort study

Deep immune profiling of COVID-19 patients reveals distinct immunotypes with therapeutic implications

Next generation sequencing of T and B cell receptor repertoires from COVID-19 patients showed signatures associated with severity of disease

SARS-CoV-2-reactive T cells in healthy donors and patients with COVID-19

Phenotype and kinetics of SARS-CoV-2-specific T cells in COVID-19 patients with acute respiratory distress syndrome

Targets of T Cell responses to SARS-CoV-2 coronavirus in humans with COVID-19 disease and unexposed individuals

Visualizing data using t-SNE

Role of aging and the immune response to respiratory viral infections: potential implications for COVID-19

Imbalance of regulatory and cytotoxic SARS-CoV-2-reactive CD4+ T cells in COVID-19

Distribution of ACE2, CD147, CD26, and other SARS-CoV-2 associated molecules in tissues and immune cells in health and in asthma, COPD, obesity, hypertension, and COVID-19 risk factors

Immune response to SARS-CoV-2 and mechanisms of immunopathological changes in COVID-19

Immunology of COVID-19: current state of the science

Pathological findings of COVID-19 associated with acute respiratory distress syndrome

Circuits between infected macrophages and T cells in SARS-CoV-2 pneumonia

Pathological study of the 2019 novel coronavirus disease (COVID-19) through postmortem core biopsies

Single-cell landscape of bronchoalveolar immune cells in patients with COVID-19

CXCR3-deficiency protects influenza-infected CCR5-deficient mice from mortality

CXCR3 directs antigen-specific effector CD4 + T cell migration to the lung during parainfluenza virus infection

CXCR3 ligands in disease and therapy

MAIT cell activation and dynamics associated with COVID-19 disease severity

Dysregulation of the immune response affects the outcome of critical COVID-19 patients

Functionality testing of stem cell grafts to predict infectious complications after allogeneic hematopoietic stem cell transplantation

Evaluation of T and B lymphocyte function in clinical practice using a flow cytometry based proliferation assay

Homeostasis of naive and memory T cells

The role of cytokines in T-cell memory in health and disease

Longitudinal immunological analyses reveal inflammatory misfiring in severe COVID-19 patients

Influenza virus infection induces functional alterations in peripheral blood lymphocytes

The human immune response to respiratory syncytial virus infection

Divergent SARS-CoV-2-specific T-and B-cell responses in severe but not mild COVID-19 patients

Longitudinal profiling of respiratory and systemic immune responses reveals myeloid cell-driven lung inflammation in severe COVID-19

Selective expression of the interleukin 7 receptor identifies effector CD8 T cells that give rise to long-lived memory cells

Functional and phenotypic characterization of tetanus toxoid-specific human CD4± T cells following re-immunization

Measles virus infection diminishes preexisting antibodies that offer protection from other pathogens

Incomplete genetic reconstitution of B cell pools contributes to prolonged immunosuppression after measles

Innate-like cytotoxic function of bystander-activated CD8(+) T cells is associated with liver injury in acute hepatitis A. Immunity

Association of interleukin 7 immunotherapy with lymphocyte counts among patients with severe coronavirus disease 2019 (COVID-19)

Baricitinib plus remdesivir for hospitalized adults with covid-19

Interleukin-2 signals converge in a lymphoid-dendritic cell pathway that promotes anticancer immunity

Receptor-gated IL-2 delivery by an anti-human IL-2 antibody activates regulatory T cells in three different species

Palladium-based mass tag cell barcoding with a doublet-filtering scheme and single-cell deconvolution algorithm

A practical guide to multiplexed mass cytometry

Transient partial permeabilization with saponin enables cellular barcoding prior to surface marker staining

AirLab: a cloud-based platform to manage and share antibody-based singlecell research

CyTOF workflow: differential discovery in high-throughput high-dimensional cytometry datasets

Data-driven phenotypic dissection of AML reveals progenitor-like cells that correlate with prognosis

An R-based reproducible and user-friendly preprocessing pipeline for CyTOF data

Jo ur na l P re of

IL-17 receptor A and adenosine deaminase 2 deficiency in siblings with recurrent infections and chronic inflammation