CD4 is a type I transmembrane glycoprotein expressed on most thymocytes and the helper/inducer subpopulation of mature T lymphocytes of all mouse strains tested. CD4 has also been detected at low density on pluripotent hematopoietic stem cells, bone marrow myeloid precursors, and intrathymic lymphoid precursors. The CD4 antigen functions as a co-receptor, interacting with class II major histocompatability complex (MHC) molecules in the recognition of foreign antigens by T cells. In vivo and in vitro treatment with the GK1.5 monoclonal antibody effectively depletes CD4+ cells. GK1.5 also blocks helper T cell responses to MHC class II antigens, including cytolysis, proliferation, allogeneic B cell help, and release of lymphokines.
BALB/c mouse splenocytes were stained with Rat Anti-Mouse CD4-APC/CY5.5 (SB Cat. 1540-18) and Rat Anti-Mouse CD8α-FITC (SB Cat. No. 1550-02).