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Figure S1. B5 and B7 T cell epitopes of MSP1 protein. The B5 hybridoma recognizes an epitope (MSP1 aa 1,157-1,171) located within the p39 fragment of the MSP1 protein that is cleaved upon merozoite invasion of the RBC. This fragment is processed in early endosomes and presented on recycling H-2Ed molecules (Quin, S.J., E.M. Seixas, C.A. Cross, M. Berg, V. Lindo, B. Stockinger, and J. Langhorne. 2001. Eur. J. Immunol. 31:72-81). B7 epitopes are processed from the p21 fragment of the MSP1 protein (MSP1 aa 1,690-1,709), which remains attached to the merozoite membrane. This epitope is released in the late endosome/lysosome after the reduction of several disulphide bonds and presented on newly synthesized H-2Ad molecules (Quin, S.J., E.M. Seixas, C.A. Cross, M. Berg, V. Lindo, B. Stockinger, and J. Langhorne. 2001. Eur. J. Immunol. 31:72-81).