Experimental infection of cats with Bartonella henselae resulted in rapid clearance associated with T helper 1 immune responses.

Six cats were inoculated with Bartonella henselae strains A and B, which were isolated from the same naturally infected cat. The numbers of CD4(+) cells decreased following the infection. The levels of bacteremia were significantly correlated with the expression levels of IFN-gamma mRNA during the various stages of bacteremia and elimination of the bacteremia. Furthermore, the lower levels of TNF-alpha mRNA expression during the bacteremia related to the emergence of higher levels of bacteremia. These results indicate that the activation of cell-mediated immune responses, including IFN-gamma and TNF-alpha production, play an important role in elimination of B. henselae from bacteremic cats.