CD40LG and infection: Figure 5A indicates that naïve splenic B cells contain a cell fraction that is highly responsive to IgM Fab activation and proliferation. This fraction is absent in spleens of T. brucei infected C57Bl/6 mice 10 days after infection (Fig. 5B). Also when cells were stimulated in a non-specific manner with LPS, naïve CD19+ B cells showed a dose dependent proliferative response (Fig. 5C), while infection derived affected B cells showed a complete inhibition of LPS-mediated proliferation (Fig. 5D).