In vitro generation of tumour-specific lymphocyte reactivity to colonic carcinoma cells. Comparison with normal colonic mucosa cells.

Purified tumour cells and normal mucosa cells from fresh human colorectal cancer resection specimens, and T-cell-enriched autologous peripheral blood lymphocytes, were mixed in short-term (6 day) mixed lymphocyte-tumour cell (MLTC) microcultures. Lymphocyte stimulation was measured by 3H-thymidine uptake, and a stimulation index (SI = [lymphocytes vs tumour cells (cpm)-tumour cells (cpm)]/[lymphocytes (cpm)] greater than 3 was regarded as significant. Significant lymphocyte reactivity was found in 10/15 patients with colon carcinoma. However, 1 patient with autologous tumour reactivity, also showed significant stimulation against autologous normal mucosa cells, suggesting tumour-associated reactivity. Maximum stimulation occurred most frequently at a lymphocyte:tumour cell ratio of 2:1 and with nylon wool-passaged lymphocytes.