CD4 is a glycoprotien expressed on the surface of Helper T Cell

CD4+ or T-helper cell.

CD4+ or T=helper cell.

CD4

CD4 is a surface receptor expressed by helper T lymphocytes, known as CD4+ T cells. Its purpose is to stablize the interaction between the T cell receptor (on the T cell) and an antigen-bearing MHC Class II molecule (on an antigen presenting cell).

Under the right circumstances, this interaction activates CD4+ T cells that recognize an invading pathogen. Activated CD4+ T cells do many things, and are required for a robust adaptive immune response.