B5 T cells make cytokines to parasite infection in RAG mice. B5 and BALB/c CD4⁺ cells were purified (> 99% CD4⁺) by high-speed flow cytometry and transferred into RAG^-/- mice, which were then infected with 10⁴P chabaudi parasites. Some mice were immunized with the T-cell antigen (MSP1_900-1507) covalently linked to a protective B-cell antigen (MSP1₂₁). (A-C) On days 7 and 15, splenocytes were analyzed by flow cytometry for surface expression of activation markers CD45RB and CD69 and intracellular IFN-γ, IL-2, and IL-10. Cells shown are lymphocyte gated CD4⁺Vβ8⁺ B5 T cells. n.d. indicates not determined.