CD4

CD4 is a type I transmembrane glycoprotein that mainly exists in helper T cells (Th). It can bind to MHC II of antigen presenting cells in conjunction with T cell receptors to increase T cell antigen sensitivity and initiate activation programs. In clinical practice, CD4 is expressed in skin diseases such as mycosis fungoides, Sezary syndrome, and primary cutaneous CD4+ small/medium T cell lymphoproliferative disorder. Meanwhile, research on CD4+ follicular helper T cells is beneficial for the diagnosis and prognosis of various diseases such as vascular angioimmunoblastic T cell lymphoma, diffuse large B cell lymphoma, follicular lymphoma, acute myeloid leukemia, chronic lymphocytic leukemia, etc. Moreover, different CD4+ T cells have different mechanisms. In lung cancer, liver cancer, gastric cancer, colorectal cancer, breast cancer, ovarian cancer and other malignant diseases, cytotoxic CD4+ T cells and Th1 can enhance tumor immune response, but regulatory T cells and Th17 can mediate immune escape and angiogenesis of tumors.