The local immune response to large bowel tumors

Methods are described for the purification on isokinetic gradients of isolated large bowel lamina propria lymphocytes (LPL) and large bowel adenocarcinoma-infiltrating lymphocytes (TIL). The in vitro cytotoxic and proliferative responses of these lymphocytes and of peripheral blood lymphocytes from tumor patients were assayed. Neither K cell nor NK cell cytotoxic activity was detected in LPL and TIL, although both types of lytic response were present in PBL. Lectin-induced cytotoxicity was mediated by LPL and TIL populations, but their responses in this assay were reduced comparable to that of PBL. Although TIL comprised equivalent T cell proportions to PBL, the proliferative response of TIL T cells was comparatively lower. LPL and TIL populations, but their responses in this assay were reduced comparable to that of PBL. Although TIL comprised equivalent T cell proportions to PBL, the proliferative response of TIL T cells was comparatively lower. Co-culture experiments and attempts to induce suppressor cells with concanavalin A suggested that the reduced proliferative response of T cells infiltrating these tumors was not due to the action of suppressor lymphocytes.