Expansion of a subset of TCR gamma/delta human lymphocytes from various lymphoid organs cultured with recombinant IL-2.

1. TCR1 cells are a minor component of CD3+ lymphocytes which bear the gamma/delta T-cell receptor. There are limited data concerning the activation of TCR1 cells or TCR1 cell subsets in human lymphoid organs. We analyzed a subset of TCR1 cells (delta TCS1+) in peripheral blood (PBL), spleen (SPL), lymph nodes (LN), bone marrow (BM), and thymus (THY) after activation with IL-2. Lymphoid cells from these organs were cultured with 1500 U/ml IL-2 for 14 days and analyzed at periodic intervals for delta TCS1+ cells. 2. We found increased numbers of delta TCS1+ cells in 6- and 14-day cultures from SPL (20.8 +/- 11.8% positive cells after 14 days of culture), LN, BM and THY but not in peripheral blood (1.8 +/- 0.9%). These delta TCS1+ cells coexpressed CD2, CD3, CD8 and CD56, but were negative for TCR alpha/beta and CD4. We also detected an expansion of TCR1+ cells in IL-2-stimulated PBL employing the pan-gamma/delta marker TCR delta 1; however, in contrast to solid organs, these TCR1+ cells were delta TCS1 negative. 3. Sorting experiments demonstrated directly that delta TCS1 cells from spleen cultures mediate high cytotoxic activity against K562 cell targets (39.4% median specific cytotoxicity) and low activity against Daudi (9.6%), COLO (2.7%) and an antibody-sensitized human B-cell line (17%). 4. These results show expansion and cytotoxic activation by IL-2 of a subset of human TCR1 cells in solid lymphoid organs.