Sclerostin domain-containing protein 1 is dispensable for the differentiation of follicular helper and follicular regulatory T cells during acute viral infection.

T follicular helper (TFH) cells are crucial for effective humoral immunity by providing the required signals to cognate B cells and promoting germinal center (GC) formation. Many intrinsic and extrinsic factors have been reported to be involved in the multistage, multifactorial differentiation process of TFH cells. By comparing gene expression between TFH cells and TH1 cells based on published GEO data, we found selective and high expression of sclerostin domain-containing protein 1 (SOSTDC1) in TFH cells but not in TH1 cells; however, it is unclear whether SOSTDC1 is important for the differentiation and/or function of TFH cells. Using a mouse model of acute lymphocytic choriomeningitis virus (LCMV) infection, we confirmed the selective expression of SOSTDC1 in TFH cells compared to that in TH1 cells, but the ablation of SOSTDC1 did not affect TFH cell differentiation or effector function. Thus, our results indicate that the SOSTDC1 protein is merely a specific marker of TFH cells but does not play a functional role in the differentiation of TFH cells during acute viral infection.