To further examine the role of B cell antigen presentation on CD4+ T cell responses to Brucella, we compared control of infection in B cell specific MHCII deficient mice (CD19CreiABfl/fl) and iABfl/fl control animals and found B cell specific MHCII deficiency enhanced resistance to Brucella four weeks post infection (Fig 2B). This evidence concerns the gene CD4 and infection.