CD4 and viral infectious disease: In these patients, absolute counts and percentages of lymphocytes including CD4 Lymphocytes T (CD4+ T), CD8 cytotoxic lymphocytes (CD8+ cytotoxic T), natural killer (NK), and B cells are reduced as well, possibly as a consequence of both the direct cell death secondary to viral infection, and the exhaustion and depletion of T cells driven by circulating chemokines.