Role of strain differences on host resistance and the transcriptional response of macrophages to infection with Yersinia enterocolitica

The outcome of a host-pathogen encounter is determined by virulence factors of the pathogen and defense factors of the host. We characterized the impact of host factors [ resistant (C57BL/6) or susceptible (BALB/c) genetic background and exposure to interferon (IFN)-gamma] on transcriptional responses of bone marrow-derived macrophages (BMDM) to infection with Yersinia enterocolitica. IFN-gamma treatment more profoundly altered the transcriptome of BMDM than did bacterial infection or genetic background. In BALB/c BMDM, 1,161 genes were differentially expressed in response to Yersinia infection with or without IFN-gamma prestimulation. Fourteen genes (1.2%) could only be induced by BALB/c BMDM in response to Yersinia infection after IFN-gamma pretreatment. These genes inhibit apoptosis, activate NF-kappa B and Erk signaling, are chemotactic to neutrophils, and are involved in cytoskeletal reorganization, hence possibly in phagocytosis. Ten of these genes possess a common module of binding sites for Hox, Pou, and Creb transcription factors in 2 kb of upstream genomic sequence, suggesting a possible novel role of these transcription factors in regulation of immune responses. Fifty-two of one thousand fifty differentially expressed genes (4.9%) were induced more strongly by C57BL/6 BMDM in response to Yersinia infection than BALB/c BMDM. These genes activate NK cells, have antibacterial properties, or are involved in sensing chemokines and lipopolysaccharide (LPS). These data show that host resistance factors modulate a surprisingly small, but identifiable and functionally significant, portion of the macrophage transcriptome in response to Yersinia infection.