IN-VIVO AND IN-VITRO ACTIVATION AND EXPANSION OF GAMMA-DELTA T-CELLS DURING LISTERIA-MONOCYTOGENES INFECTION IN HUMANS

Serial flow cytometry analyses of peripheral blood mononuclear cells o btained from 8 patients infected with Listeria monocytogenes showed a higher percentage (P < 0.01) of gamma delta T cells (median, 11.7; ran ge, 3.7 to 353) than did 16 age-matched uninfected controls (1.7, 0.4 to 13). Most in vivo-expanded gamma delta T cells expressed the V gamm a 9 and V delta 2 gene products and displayed a memory phenotype (CD45 RO(high)), and patients' gamma delta T cells expressed significantly m ore (P < 0.01) activation marker HLA-DR than did controls (19.8% [medi an] and 0.9 to 87.6% [range] versus 2.3% and 0 to 4.7%, respectively). When peripheral blood mononuclear cells from normal donors were cultu red in vitro with heat-killed Listeria cells, analysis of CD25 and HLA -DR expression on gamma delta and alpha beta T cells indicated that a high percentage of gamma delta T cells was activated early compared to alpha beta T cells. In addition, depletion of gamma delta T cells bef ore culture abrogated the early lymphocyte proliferative response indu ced by the pathogen, Taken together, these results argue for the invol vement of gamma delta T cells during L. monocytogenes infection in hum ans.