T-cell co-operation in the mediation of acquired resistance to Listeria monocytogenes.

Monoclonal antibodies were used to select T-cell subsets that mediate delayed-type hypersensitivity (DTH) and acquired cellular resistance (CRI) in rats infected with Listeria monocytogenes. The mediators of DTH were identified as W3/25+ OX8- T cells. The latter comprised a subset distinct from that which could protect recipient rats against a Listeria challenge. The protective T cells had a W3/25- OX8+ phenotype. The T-cell mediators of cellular resistance to infection (TCRI) failed to augment the expression of DTH; however, the mediators of DTH (TDTH) significantly enhanced the protective capacity of TCRI. This property of TDTH correlated with the ability of the cells to promote the focal deployment of TCRI and macrophages at sites of soluble Listeria antigen injection in skin, and in peritoneal exudates induced by killed L. monocytogenes. These findings illustrate the co-operative interaction of activated T cells in acquired resistance to L. monocytogenes, and imply that DTH has a purposeful role in the host defence against infection.