Themis differentially regulates T follicular helper cell differentiation during early and late stages of chronic viral Infection

TFH cells play an important role in chronic viral infection by helping B cells produce antibodies. Recent studies have identified a novel CD4+ T cell progenitor population in chronic LCMV infection that sustains the differentiation of TFH and other effector CD4+ T cells. However, the details of this differentiation process remain unclear. Here, we report an unprecedented dual role for Themis in regulating the differentiation of CD4+ T cell progenitors into TFH cells during chronic LCMV infection. Themis expression is strongly upregulated in TFH cells at early stages of infection, and as expected, Themis promotes TFH cell differentiation at this stage. However, unexpectedly, at the late stages of chronic LCMV infection, Themis-deficient CD4+ T cells favored TFH cell differentiation and helped control the virus by enhancing GC responses and antibody production, suggesting that Themis inhibits TFH cell differentiation at this stage. In the late stage we found that Themis inhibits the differentiation of CD4+ T cell progenitors into TFH cells through transcriptional regulation. Overall design: Primary murine tissues were collected from co-transfer p14 mice, with tissues isolated at different time points following infection with LCMV-clone 13. A total of 2 single-cell samples were prepared, consisting of CD4+ T cells from spleen tissues, with both wild-type (WT) and knockout (KO) groups, at 21 days post-infection (dpi). The isolated single-cell suspensions were processed using the DNBSEQ platform, which was run on the DNBelab C4 portable single-cell system (BGI). This system facilitates high-throughput cell capture and gene expression profiling.