IL-12/β2-microglobulin knockout mice infected with B. abortus 2308 have shown increased numbers of bacterial load in spleens as compared to C57BL/6 mice [53] and administration of anti-IL-12 monoclonal antibodies to B. abortus 19 infected CBA mice led to an exacerbation of the infection [54]. This evidence concerns the gene HLA-G and infection.