CD4 and infection: Activated Th1 CD4 T cells and effector CD8 T cells (Moser and Loetscher, 2001; Hu et al., 2011) express this receptor, and promote migration of activated CD8 T cells into non-lymphoid tissue infection sites under the influence of the chemokine ligands CXCL9 and CXCL10 (Weng et al., 1998; Christensen et al., 2006).