Most T cells express the alphabeta TCR (T cell receptor) protein and have a helper (CD4+) or cytotoxic (CD8+) phenotype.

A subset of cytotoxic T cell also express NK associated antigens and have been called “NK-like” T-cells.

A small population of T cells express the gammalamda TCR and usually have a double negative (CD-CD8-) phenotype, although some may express CD8 or more rarely, CD4. Normal gammalamda T cells are preferentially located at the extranodal sites such as the slenic red pulp, gastrointestinal tract, and skin.