Investigating the role of DOCK8 in T follicular helper cells positioning and function in germinal centers

T follicular helper (Tfh) cell migration into germinal centers (GC) is essential for the generation of GC B cells and antibody responses to T dependent (TD) antigens. This process requires interactions between LFA-1 on Tfh cells and ICAMs on B cells. The mechanisms underlying defective antibody responses to TD antigens in DOCK8 deficiency are incompletely understood. We show that mice selectively lacking DOCK8 in T cells have impaired IgG antibody responses to TD antigens, decreased GC size, and reduced numbers of GC B cells. However, they develop normal numbers of Tfh cells with intact capacity for driving B cell differentiation into a GC phenotype in vitro. Notably, migration of DOCK8 deficient T cells into GCs is defective. Following TCR/CD3 ligation, DOCK8 deficient T cells have impaired LFA-1 activation and reduced binding to ICAM-1. DOCK8 is important for LFA1-dependent positioning of Tfh cells in GCs, and thereby the generation of GC B cells and IgG antibody responses to TD antigen. RNA seq analysis of mouse T follicular helper (Tfh) (CD4+CD19-CD25-CXCR5+ICOS+) sorted from popliteal and inguinal Lymph nodes of Cd4-CreTgDock8flox/flox and control mice immunized in the hock with TNP-KLH