Human γ/δ T-cell response to <em>Listeria monocytogenes</em> protein components <em>in vitro</em>.

Listeria monocytogenes is a facultative intracellular pathogen that replicates inside mononuclear phagocytes and induces specific cellular immunity. Listeriosis encompasses many clinical syndromes and meningitis is the most frequent clinical manifestation. Human α/β and γ/δ T cells have been shown to respond to L. monocytogenes antigens and to play an important role in resistance against listerial infection. We investigated the nature of listerial ligands and the influence of the major virulence factor, listeriolysin (hly), on the stimulation of human γ/δ T cells from healthy individuals. We found that a listerial somatic protein ligand, which is sensitive to proteinase treatment, stimulated γ/δ T cells in vitro; the majority of Listeria-responsive γ/δ T cells expressed Vγ9Vδ2 T-cell receptor chains and human leucocyte antigen-DR molecules; γ/δ T-cell responses to hly⁺ and hly^- Listeria strains were comparable; L. monocytogenes strains of different virulence stimulated γ/δ T cells equally. Thus, protein components of L. monocytogenes unrelated to virulence activate human γ/δ T cells in vitro. [ABSTRACT FROM AUTHOR]