Increase in the proportion of granulated CD56 + T cells in patients with malignancy

SUMMARY Evidence is presented for the existence of a unique T cell population which expressed one of the natural killer (NK) markers, CD56 antigen, in humans. Although such 0056 + T cells were a minor population in the peripheral blood (< 10%). They were abundant in the liver (up to 50%). which was recently demonstrated to be a major organ for extrathymic T cell differentiation in mice. As in the case of extrathymic T cells in mice, these CD56 + T cells in humans contained a higher proportion of γδ cells than did CD56 − T cells, contained double‐negative CD4 −8 cells, and had the morphology of large granular lymphocytes. This unique population of CD56 + T cells tended to be elevated in the blood and among tumour‐infiltrating lymphocytes in patients with colorectal cancer, especially in advanced cases. These results raise the possibility that, as in mice, CD56 + T cells with extrathymic T cell properties may also be associated with tumour immunity in humans.