CD4 and infection: Upon recognizing cognate antigens presented by antigen-presenting cells (APCs), naive CD4 + T cells differentiate into various phenotypes, including T-helper 1 (Th1), Th2, Th17, and regulatory T cells (Tregs), which are influenced by environmental cytokines.[64–70] Tregs play a vital role in maintaining immune homeostasis, limiting excessive immune responses after infection to prevent tissue damage.[71] The presence of CD39+-secreting CD4 regulatory T cells may act as a protective factor for patients with sepsis by preventing excessive immune responses that could lead to self-inflicted harm.