Spontaneous cytotoxicity ofintestinal intraepithelial lymphocytes: clues tothemechanism

SUMMARY Humanintestinal intraepithelial lymphocytes (IEL) demonstrate target cell-restricted spontaneous cytotoxic (SC)activity thatisduetoCD2+CD3+CD8+CD16-CD56-effector cells; theykill epithelial cell (EC)tumours(such asDLD-Icolon cancercells), butnotnatural killer (NK)-sensitive K-562cells. Thepresent study showsthatthemeasured levels ofSCactivities byIELcorrelated with thoseofautologous laminapropria lymphocytes (LPL), butnotwiththoseofperipheral blood lymphocytes (PBL). Also, thesusceptibilities ofDLD- 1 cell clones tolysis byIELandPBLeffector cells didnotcorrelate, suggesting different mechanisms oflysis. Antibody blocking experiments showedthatthemainsurface molecules involved inlysis depended on theeffector celltype: aE#7 (HML-l) on IELandCD16on PBL.No antibody-dependent cell-mediated cytotoxicity (ADCC) was demonstrated byIEL,even after stimulation withinterferon-gamma (IFN-y). Few IEL expressed Fcreceptors forIgG.Thisstudy describes further differences between theSCactivities of IELandPBL.