CCR2 and infection: Ccr2, Ccl3, and Il1b had their expression increased by the infection (P < 0.001; P < 0.01; and P < 0.001, respectively); however, unlike other genes tested that were also affected by BM (Mmp9, Tjp2, Ocln, Timp1, Ccl2, Il6, Casp3, Nfkb, Tnfa, Il10, and Cxcl1) (Additional file 2), their increased expression was attenuated by adjuvant B12 (P < 0.05; P < 0.01; and P < 0.01, respectively) (Fig. 5).