CD4+ T cells
Lymphopenia is one of the predominant phenotypes in COVID-19 patients
[25-27], which is further evidenced by scRNA–seq analysis revealing
a reduction in total and subsets of CD4+ T cells after
SARS-CoV-2 infection [28, 29].
Both naive and Th1
CD4+ T cells were reduced, especially in severe
patients [23, 30], which might be correlated with the less
expression of TBX21 and the lower TBX21 locus
accessibility by integrates analysis of the single-cell assay for
transposase accessible chromatin (ATAC)-seq and scRNA-seq [30]. The
elevated expression of gene sets in metabolic and apoptotic pathways of
CD4+ T cells contributed to T cell lymphopenia
[29].
However,
Wauters et al performed single-cell deep immune profiling of
bronchoalveolar lavage samples and found that CD4+Th1-like-cells expressing TBX21 and RUNX3 were increased in
critical COVID-19 patients compared to mild COVID-19 patients [31].
Moreover, the ZFP36 , which was reported to restrain T cell
expansion and effector functions [32] was downregulated in moderate
and severe recovery patients and might be associated with Th1 proportion
recovery [33]. To dissect the exact roles of CD4+T cells, a better understanding of their subsets and status in COVID-19
patients is needed.