Diverse populations of T cells with NK cell receptors accumulate in the human intestine in health and in colorectal cancer.
Populations of cytotoxic CD3+CD56+ cells were selectively expanded when monocyte-depleted human PBL (M(-) PBL) were cultured with 20 U/ml IL-12 and 100 U/ml IL-2. In a majority of cases, CD4-CD8- as well as CD8+ gammadelta T cells with CD56 Ag were induced, but in some cases CD4+CD56+ alphabeta T cells were selectively increased. Determination of which will increase, gammadelta or alphabeta T cells, apparently is dependent upon individuals. When M(-) PBL were stimulated with IL-12 and IL-2 in the presence of immobilized anti-CD3 Ab, CD8+CD56+ alphabeta T cells increased exclusively. When M(-) PBL were cultured by IL-2 alone, CD3+CD56- cell expansion was predominant while CD3+CD56+ cells remained a minor population. Cytotoxic activity of M(-) PBL cultured with a combination of IL-12 and IL-2 is much greater than when cultured with IL-2 alone. The cytotoxicity of activated M(-) PBL was abrogated by the depletion of either CD3+ or CD56+ cells irrespective of their gammadelta or alphabeta phenotypes. These types of cells are preferentially present in the livers of humans. The results revealed that, under certain conditions, IL-12 synergizes with IL-2 to induce potent cytotoxic T cells with CD56 Ag of humans, and suggest that these cells in the human liver are functionally similar to NK1+ alphabeta T cells in murine liver.