Lymphocytes expressing gamma/delta antigen receptors constitute a minor population in lymphoid tissue, but a major population within epidermal, gastraintestine, and vaginouterine epithelia. Gamma/Delta T cells are involved in immunological surveillance of epithelia separating the external environment from the internal milieu. The GL2 antibody reacts with Vdelta4 T-cell receptor (TCR) bearing T cells, which are the predominant gamma/delta T cells in intestinal epithelium (gamma/delta IEL). Gamma/delta T cells has been found in mammary glad as well. The frequency of Vdelta4 TCR-bearing cells varies among inbred strains of mice.