BALB/c recipients with GVHD had very low to no detectable B cells, CD4 T cells, or CD8 T cells in peripheral blood as compared with transplanted control mice without GVHD (Figure 2A), suggesting that loss of MCMV control in recipient mice with GVHD was caused by profound GVHD-induced immunodeficiency. Here, CD4 is linked to immune system disorder.