Resident pulmonary lymphocytes expressing the gamma/delta T-cell receptor

The biological role of cells bearing the gamma delta T-cell antigen receptor (TCR) is as yet unclear. Although there are indications that some gamma delta+ cells can mediate cytotoxicity, their antigen-related functions have not yet been defined. In the mouse, gamma delta+ cells constitute 1-3% of T cells in lymphoid organs. Intestinal intraepithelial lymphocytes (IELs) and dendritic epidermal cells (DECs) also appear to carry the gamma delta TCR. The strategic locations of DECs and IELs have led to the suggestion that gamma delta+ cells could constitute a first line of defence in the vicinity of large surfaces of contact with the environment. We report here that an estimated 8-20% of resident pulmonary lymphocytes (RPLs) are CD3+ alpha beta TCR-, and presumably gamma delta TCR+. Furthermore, mice exposed to aerosols containing a Mycobacterium tuberculosis extract have an increased number of activated CD3+ alpha beta-TCR- pulmonary T cells which can be propagated in vitro.