Another study found that CD4+ T lymphocytes in COVID-19 patients are rapidly activated to become pathogenic T-helper (Th) 1 cells and produce granulocyte macrophage colony-stimulating factor and other cytokines, further inducing the generation of CD14+CD16+ monocytes that produce high levels of IL-6 and consequently accelerating the inflammatory response. Here, CD4 is linked to COVID-19.