Different appearance of gamma delta T cells during salmonellosis between Ityr and Itys mice.

Ity gene, which is believed to be a single gene on proximal mouse chromosome 1, determines susceptibility to Salmonella infection. We have recently demonstrated that the gamma delta T cells specific for purified protein derivative appear at the early stage after infection with Salmonella choleraesuis strain 31N-1 (avirulent strain) in mice. In the present study, we compared the appearance of the gamma delta T cells in Ityr and Itys mice after infection with S. choleraesuis in an attempt to elucidate the role of the gamma delta T cells in the in vivo effect of the Ity locus on murine salmonellosis. The numbers of gamma delta T cells in the peritoneal cavity and liver were significantly larger in DBA/2 (Ityr) mice than those in BALB/c (Itys) mice after infection with a sublethal dose of S. choleraesuis. C.D2 Ityr mice, which are BALB/c mice with Ityr allele, also showed a significant increase in the number of the gamma delta T cells at the early stage after infection. Similar results in different appearances of the gamma delta T cells could be obtained between BALB/c and DBA/2 mice after infection with Mycobacterium bovis, bacillus Calmette-Guérin. The peritoneal adherent cells of DBA/2 mice infected with S. choleraesuis, which expressed a large amount of heat shock/stress protein (hsp) homologous to the mycobacterial 65-kDa hsp, induced significantly higher level of expansion of the peritoneal gamma delta T cells in normal mice in vivo and in vitro than did those of BALB/c mice infected with S. choleraesuis, which expressed a lesser amount of the hsp. These results suggest that the Ity locus may be closely related to the expression of hsp by macrophages after infection with Salmonella, which in turn stimulate the gamma delta T cells in the host during an early phase of salmonellosis.