A NEW SURFACE-ANTIGEN ON INTRAEPITHELIAL LYMPHOCYTES IN THE INTESTINE

A new surface molecule has been discovered on mouse intestinal intraepithelial lymphocytes (IEL) using a rat anti‐mouse IEL monoclonal antibody, M290. It was expressed at high levels on nearly all IEL and on a majority of T cells in the gut lamina propria. M290 stained, with lower intensity, a small minority of T cells in other lymphoid tissues. Expression was biased towards the CD8+ subset. Stimulation of peripheral T cells with mitogens did not induce expression of the new antigen but addition of transforming growth factor β to stimulated T cells had a marked inductive effect. Sodium dodecyl sulfate‐polyacrylamide gel electrophoretic analysis of IEL surface components precipitated with M290 showed principal bands at 135, 120, 28 and 24 kDa (reduced) and 135, 100, 24 and 21 kDa (nonreduced). Precipitation with antibodies to integrin subunits showed that the new molecular complex was not a member of the β1, β2, or β3 integrin families although all of these were represented on IEL. A 13‐amino acid N‐terminal sequence obtained from the 120‐kDa β subunit of the antigen prepared from an M290+ Thybridoma (MTC‐1) did not show homology with integrins. Pulse‐chase studies using MTC‐1 cells showed that the 135‐kDa α subunit was derived from a 147‐kDa precursor. The function of this new molecular complex is not yet known. Copyright © 1990 Wiley‐VCH Verlag GmbH & Co. KGaA