Germinal center formation is resilient to CD69 deletion on T follicular helper cells

T follicular helper (T FH ) cells are a helper T‐cell subset that is defined by their localisation to B‐cell areas of secondary lymphoid tissues, enabling them to provide their B‐cell helper function. Precursors of T FH cells migrate to the B‐cell follicles by upregulating CXCR5 and downregulating CCR7, a process that can be blocked by S1PR1 overexpression. T FH cells and their precursors also express the early activation antigen CD69, which is a negative regulator of S1PR1. In this study, we tested the hypothesis that CD69 expression by T FH cells is important for their differentiation and localisation after immunization. Genetic deletion of CD69 on T FH cells and a proportion of their precursors did not alter their formation, nor their ability to support high‐affinity B‐cell responses. This demonstrates that although CD69 is expressed highly on T FH cells, it is not necessary for their formation or their B‐cell helper functions in lymph nodes (LNs).