CD4 T cell

Patent Pending Mature Th cells express the surface protein CD4 and are referred to as CD4+ T cells. CD4+ T cells are generally treated as having a pre-defined role as helper T cells within the immune system. For example, when an antigen presenting cell expresses an antigen on MHC class II, a CD4+ cell will aid those cells through a combination of cell to cell interactions (e.g. CD40 and CD40L) and through cytokines. Nevertheless, there are rare exceptions; for example, sub-groups of regulatory T cells, natural killer T cells, and cytotoxic T cells express CD4. All of the latter CD4+ T cell groups are not considered T helper cells.