Accessing Early Differentiation of Virus-Specific Follicular Helper CD4 + T Cell in Acute LCMV-Infected Mice

Follicular Helper T (T-FH) cells are perceived as an independent CD4 (+) T cell lineage that assists cognate B cells in producing high-affinity antibodies, thus establishing long-term humoral immunity. During acute viral infection, the fate commitment of virus-specific T-FH cells is determined in the early infection phase, and investigations of the early-differentiated T-FH cells are crucial in understanding T cell-dependent humoral immunity and optimizing vaccine design. In the study, using a mouse model of acute lymphocytic choriomeningitis virus (LCMV) infection and the TCR-transgenic SMARTA (SM) mouse with CD4 (+) T cells specifically recognizing LCMV glycoprotein epitope I-A(b)GP 66-77 , we described procedures to access the early fate commitment of virus-specific T-FH cells based on flow cytometry stainings. Furthermore, by exploiting retroviral transduction of SM CD4 (+) T cells, methods to manipulate gene expression in early-differentiated virus-specific T-FH cells are also provided. Hence, these methods will help in studies exploring the mechanism(s) underlying the early commitment of virus-specific T-FH cells.