CD244 and HIV infectious disease: Negative checkpoint regulators (NCRs) such as cytolytic T lymphocyte-associated antigen-4 (CTLA-4), T-cell immunoglobulin mucin-3 (TIM-3), programmed death-1 (PD-1), 2B4 (CD244), lymphocyte activation gene-4 (LAG-3), and CD160 play a critical role in the regulation of anti-viral CD8+ T cell responses during human immunodeficiency virus (HIV) infection (8).