Both antibodies and T cells have been shownto contribute towardhost-mediated protection against C. burnetii infection.While antibodies play an important role during the early stages ofextracellular infection, T cell activation is vital for clearanceof intracellular bacteria.87 Of particularsignificance are Th1 cells, identified by class switched B cells toproduce IgG2c and IFN-γ positive CD4 T cells. The gene discussed is CD4; the disease is infection.