CD4 and atherosclerosis: Global MHCII deletion causes congenital CD4+ T-cell deficiency; thus, it is not an appropriate model to study T-cell/B-cell interactions.59 Using a mixed BM Ldlr−/− chimera model (Table 2), Tay et al10 found B cell–selective MHCII deletion decreased TFH and GC B cells without changing IgM levels, leading to decreased early atherosclerosis in comparison to nonlittermate WT mice.