Different appearance of γδ T cells during salmonellosis between Ity(r) and Ity(s) 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 γδT 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 γδT cells in Ity(r) and Ity(s) mice after infection with S. choleraesuis in an attempt to elucidate the role of the γδT cells in the in vivo effect of the Ity locus on murine salmonellosis. The numbers of γδT cells in the peritoneal cavity and liver were significantly larger in DBA/2 (Ity(r)) mice than those in BALB/c (Ity(s)) mice after infection with a sublethal dose of S. choleraesuis. C.D2 Ity(r) mice, which are BALB/c mice with Ity(r) allele, also showed a significant increase in the number of the γδ T cells at the early stage after infection. Similar results in different appearances of the γδ T cells could be obtained between BALB/c and DBA/2 mice after infection with Mycobacterium bovis, bacillus Calmette-Guerin. 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 γδ 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 γδ T cells in the host during an early phase of salmonellosis.