In contrast, these same organs in BALB/c mice contain persistent levels of organism 8 weeks p.i. and beyond (Kahl-McDonagh et al., 2007) . These results are consistent with previous reports describing enhanced sensitivity of BALB/c mice to Brucella infection following i.p. inoculation (Copin et al., 2007) , confirming the expected immunological outcome despite the use of different routes of inoculation. One explanation for the improved clearance from C57BL6 mice is generation of a TH1-skewed immune response as opposed to a TH2-skewed response in BALB/c mice (Watanabe et al., 2004) . TLR activation induces the maturation of APCs, enhances antigen presentation, up-regulation of co-stimulatory molecules and cytokine production. Cytokine profiles produced by APCs control CD4 + T cell differentiation into either TH1 or TH2 cells. Engagement of different TLRs is expected to affect cytokine production, with significant effect on CD4 + T cell differentiation (Dabbagh and Lewis, 2003) . Previous studies have shown that Brucella infection induces mainly a TH1 response during acute disease (Agranovich et al., 1999; Pasquali et al., 2001; Giambartolomei et al., 2002; Rafiei et al., 2006; Khatun et al., 2009) .