H2-M3 major histocompatibility complex class Ib-restricted CD8 T cells induced by Salmonella enterica serovar Typhimurium infection recognize proteins released by Salmonella serovar Typhimurium.

Salmonella enterica serovar Typhimurium causes a typhoid-like disease in mice which has been studied extensively as a model for typhoid fever in humans. CD8 T cells contribute to protection against S. enterica serovar Typhimurium in mice, but little is known about the specificity and major histocompatibility complex (MHC) restriction of the response. We report here that CD8 T-cell lines derived from S. enterica serovar Typhimurium-infected BALB/c mice lysed bone marrow macrophages infected with S. enterica serovar Typhimurium or pulsed with proteins from S. enterica serovar Typhimurium culture supernatants. Cytoxicity was beta-2-microglobulin dependent and largely TAP dependent, although not MHC class Ia restricted, as target cells of several different MHC haplotypes were lysed. The data suggested the participation of class Ib MHC molecules although no evidence for the presence of Qa1-restricted T cells could be found, unlike in previous reports. Instead, the T-cell lines lysed H2-M3-transfected fibroblasts infected with S. enterica serovar Typhimurium SL3261 or treated with Salmonella culture supernatants. Thus, this report increases the number of MHC class Ib antigen-presenting molecules known for Salmonella antigens to three: Qa-1, HLA-E, and now H2-M3. It also expands the range of pathogens that induce H2-M3-restricted CD8 T cells to include an example of gram-negative bacteria.