CD4 and graft versus host disease: Indeed, a recent study using genetic ablation of the MHCII molecule in Ccl19-Cre+ cells revealed that FRCs shape CD4+ T cells’ responses in a murine model of acute graft-versus-host disease (GVHD) with reduced expansion of FoxP3-expressing CD4+ T cells and invariant natural killer (NK) T cells (Shaikh et al., 2022).