CD4 and lymphopenia: Dysregulated immune responses in critically ill patients with COVID-19 is reflected by lymphopenia, affecting mostly CD4+ T cells, including effector, memory, and regulatory T cells, and decreased IFN-γ expression in CD4+ T cells.8 Exhaustion of cytotoxic T lymphocytes, activation of macrophages, and a low human leukocyte antigen-DR expression on CD14 monocytes has been noted in patients with COVID-19.