To determine the development of cell-mediated immunity, the splenocytes collected at 8 weeks p.i. from knockout and control mice are stimulated with Brucella antigen ex vivo. Using an LDH release assay to measure lymphocyte proliferation, no significant differences in proliferation was detected for TLR2 −/− , TLR4 −/− , MyD88 −/− and control C57BL/6 mice ( Figure 4A ). This result indicates that cell-mediated adaptive immunity against Brucella is unimpaired in these knockout mice. Consistent with the results of the lymphocyte proliferation assay, IFN-γ levels detected in splenocyte supernatants collected from the knockout mice are not significantly different from C57BL/6 mice ( Figure 4B ).