Characterization of activated lymphocytes in colon cancer.

The percentages of activated lymphocytes in colon cancers were compared to clinical features of the tumors and to functional characteristics of the tumor-infiltrating lymphocytes (TIL) in order to evaluate the role of activated TIL in controlling tumor growth. The TIL isolated from colon cancers contained 80 +/- 6% T cells [cluster designation (CD) 2+], 42 +/- 9% CD4+ cells, 27 +/- 9% CD8+ cells, 17 +/- 5% cells (surface immunoglobulin or SIg+), 6 +/- 2% null cells (CD2-, SIg-), 6 +/- 4% Leu 7+ cells, 1 +/- 0% macrophages (CDw 14+), and no plasma cells (PCA+). The lamina propria lymphocytes (LPL) isolated from adjacent colonic mucosa contained a similar distribution but with fewer CD8+ (10 +/- 5%) and Leu 7+ (0.6 +/- 0.3%) lymphocytes (P less than 0.05). More TIL than LPL expressed the interleukin-2 (IL-2) receptor (9 +/- 8% vs 1 +/- 0.8% CD25+ cells; P less than 0.05) and the transferrin receptor (4 +/- 5% vs 0.3 +/- 0.6% T9+ cells; P less than 0.05). Those TIL expressing activation antigens were CD2+, SIg-. The percentage of TIL that were CD25+ did not correlate with the extent of tumor spread, with the degree of tumor differentiation, nor with the percentage of HLA-DR+ tumor cells. However, there were significantly more CD25+ TIL from tumors located in the left colon, particularly small lesions, than from tumors located in the right colon (P less than 0.05). The proliferation of TIL preparations cultured with medium alone, with mitogens, or with IL-2 did not vary according to the percentage of CD25+ lymphocytes in the TIL. T cells may be activated by foreign surface determinants on tumor cells, particularly in small, left-sided lesions.