CD4 and inborn error of immunity: Primary immunodeficiency was specifically inhibited (p = 0.0041), reflecting the up regulation of Cd8 (marker for cytotoxic T cells), Cd3δ, Cd3ε (required for differentiation of pro-T cells into pre-T cells) and Lck (required for Cd4+Cd8+ T cell differentiation into Cd8+ T cells) [58].