Functional role of CD95 ligand in concanavalin A-induced intestinal intraepithelial lymphocyte cytotoxicity

Freshly isolated murine intestinal intraepithelial lymphocytes (IEL) express CD95 ligand (CD95L), as shown by reverse transcription-polymerase chain reaction (RT-PCR) and fluorescence-activated cell sorter (FACS) analysis. Between 15 and 25% of IEL could be stained with an antibody to CD95L. Therefore it was investigated whether the CD95L/CD95 pathway was effective in IEL cytotoxicity. Stimulation of IEL in vitro with concanavalin A (Con A) induced a strong cytotoxic response, which was much higher when using CD95-expressing target cells. This effect was most evident when comparing the specific lysis of CD95-transfected target cells of the leukaemia cell line L1210 with that of the untransfected parental cell line. In addition, an antibody to CD95 was able to dramatically reduce the specific lysis of CD95-expressing target cells. After stimulation with Con A, which is able to bind to CD95L, the effects were more obvious compared with the triggering of the T-cell receptor (TCR)-alphabeta or gamma delta. On the other hand, EGTA reduced the Con A-induced cytotoxicity. Together these findings support a role of the CD95L/CD95 pathway in IEL cytotoxicity, even though the reaction was Ca2+ sensitive. As a function, CD95L-expressing IEL should be able to contribute to the elimination of CD95-expressing target cells in the intestine.