HUMAN T-CELL RECOGNITION OF LISTERIA-MONOCYTOGENES - RECOGNITION OF LISTERIOLYSIN-O BY TCR-ALPHA-BETA(-GAMMA-DELTA(+) T-CELLS() AND TCR)

The cell-mediated immune response to Listeria monocytogenes has been w ell characterized in the mouse. Listeriolysin O (LLO) is a major antig en in murine T-cell recognition of L. monocytogenes. In this study, we show that LLO is also recognized by human TcR alpha beta T cells and TcR gamma delta T cells. Human peripheral blood mononuclear cells (PBM C) cultured in vitro with live listeriae and then expanded with interl eukin 2 were shown to respond to purified LLO. The generation of LLO-r esponsive T cells was dependent on the use of live bacteria during the initial in vitro challenge. LLO-induced proliferation of T cells expa nded by exposure of PBMC to live listeriae was major histocompatibilit y complex restricted. PBMC cultured with formalin-fixed listeriae and subsequently expanded by interleukin 2 gave high proliferative respons es to fixed bacteria but failed to respond to LLO. PBMC stimulated in vitro with fixed listeriae contained predominantly TcR alpha beta(+) T cells. In contrast, PBMC obtained from 85% of the donors studied gene rated high numbers of TcR gamma delta(+) T cells following in vitro cu lture with live listeriae. Using a panel of synthetic amphipathic LLO peptides, we found that LLO-specific T cells from different individual s recognized both common and unique peptides, LLO 470-508 was recogniz ed by three of five individuals, while LLO 203-226 and LLO 107-126 wer e recognized by two of six individuals. A TcR gamma delta(+) T-cell li ne was established from PBMC stimulated,vith live listeriae and was sh own to recognize LLO 470-508. Proliferative responses could be induced in this cell line by peptide-pulsed autologous PBMC but not by peptid e-pulsed allogeneic PBMC. Our results establish the importance of LLO in human T-cell recognition of listeriae and show that both TcR alpha beta(+) T cells and TcR gamma delta(+) T cells recognize this antigen, Finally, since LLO 470-508 has a high degree of homology with other g ram-positive bacterial toxins, the recognition of this peptide by TcR gamma delta(+) T cells suggests that an important role of these T cell s in host defense is the recognition of bacterium-derived toxins.