Identification of follicular T helper cells in tissue sections

Follicular T helper (Tfh) cells are a critical population of CD4 T helper cells that are primarily localized in the germinal centers (GCs) to help B cell maturation and antibody production. Tfh cells can be identified in tissue sections based on the expression of a panel of classical Tfh surface makers, transcription marker(s), and effector-function cytokines, as well as by their unique anatomic proximity to other GC cells, including follicular dendritic cells (FDC) and GC B cells. Here, we describe an immunofluorescence staining method for visualization of GC Tfh cells in frozen spleen tissue sections of the autoimmune BXD2 mouse using a confocal imaging strategy. Tfh cells were characterized based on the expression of CD4, CXCR5, Bcl6, IL-21, and IL-17.