CD4 and lymphopenia: To distinguish T cell-intrinsic or -extrinsic mechanism(s) under-lying peripheral T cell lymphopenia upon specific deletion of RACK1 in T cells, we created mice with mixed bone marrow through transferring bone marrow cells from congenically marked Gnb2l1F/F (CD45.1CD45.2) and Gnb2l1F/F; CD4-Cre (CD45.2CD45.2) mice into sublethally irradiated CD45.1CD45.1 mice.