AP BIOLOGY

Detailed explanation-1: -Helper T cells express a protein called CD4 on their surface. This protein plays a critical role in helper T cell activation by binding class II major histocompatibility complex (MHC) molecules, which specialize in helping the immune system recognize foreign substances.

Detailed explanation-2: -CD4 is, by contrast, a type of protein found on certain immune cells like T-cells, macrophages, and monocytes. CD4 T cells are considered “helper” cells because they do not neutralize infections but rather trigger the body’s response to infections.

Detailed explanation-3: -Helper T cells are also known as Th cells or CD4 T cells, because they have a protein called CD4 that associates with the TCR and assists in the binding of the TCR to the MHC class II molecule.

Detailed explanation-4: -CD4 is a membrane glycoprotein and a member of the immunoglobulin supergene family and a co-receptor in MHC class II-restricted T-cell activation [5, 48]. It also plays a role in the differentiation of thymocytes and the regulation of T-lymphocyte/B-lymphocyte adhesion [5, 48, 49].

Detailed explanation-5: -CD4 is found on the surface of immune cells such as T helper cells, monocytes, macrophages, and dendritic cells.