Figure 2: SEB interferes with exogenous helper memory CD4 T cell function to block B cell recall responses. Recipient BALB/c mice were primed with TNP-RGG adsorbed to alum. At 13 weeks, DO11.10 CD4+ naive and memory T cells were injected into the immune mice. 24 hours after adoptive transfer the mice were injected with either PBS or SEB, as indicated in the figure. After an additional 48 hours, all mice were challenged with an injection of TNP-OVA. Splenocytes were collected 5 days after immunization and IgM (gray) and IgG (black)-producing B cells were measured using a TNP-specific ELISPOT assay. Control mice were primed and also challenged but did not receive any donor cells. Data are from 2 pooled spleens per treatment and representative of three independent experiments.