CD5

CD5 is a type I transmembrane glycoprotein that mainly exists in T lymphocytes and B-1 lymphocytes. CD5 has dual functions. It can not only participate in initiating immune response, but also negatively regulate signal transduction of T cell receptors and B cell receptors. In clinical practice, CD5 can assist in the diagnosis of almost all T cell lymphomas. Meanwhile, CD5 can be expressed in chronic lymphocytic leukemia, small lymphocytic lymphoma, and mantle cell lymphoma, but some research found the CD5 positive follicular lymphoma, and the patients have shorter survival time compared to being negative. Similarly, some diffuse large B cell lymphoma patients with high expression of CD5 have poor prognosis, which may be because CD5 hinders the progression of tumor B cell apoptosis programs and activates multiple cell proliferation pathways. However, some scholars pointed out that CD5 is related to the good prognosis of breast cancer and non-small cell lung cancer, speculated that it may enhance the antitumor immune response by maintaining the survival of cytotoxic T cells.