Multiple CD4 T cell dependent tolerance mechanisms control adaptive B cell immunity to environmental antigens. We recently demonstrated a PD-1 checkpoint within steady-state splenic germinal centers (GC) that constrains the maturation of type 2 IgG1 isotype-specific antibody homeostasis. Here, we utilized single cell-indexed custom RNA-sequencing to probe the follicular T cell mechanisms directly targeted by acute PD-1 blockade. We find a pre-existing subset of follicular helper T (TFH) cells that express type 2 immune response properties (TFH2) with exaggerated pathways of TCR activation, cytokine signaling, and enhanced cell-cell contact upon acute PD-1 blockade. This selective amplification of the TFH2 program significantly increases predicted molecular connections to type 2 IgG1 GC B cells that dominate limited changes in GC localized follicular regulatory T (GC TFR) cell programs. These studies demonstrate how type 2 isotype-specific adaptive B cell tolerance is selectively disrupted by acute PD-1 blockade to reveal the modular regulatory mechanisms that control splenic GC dynamics at homeostasis.
This is a companion discussion topic for the original entry at https://doi.org/10.1101/2021.09.27.462076