- Protective immune responses to the 42-kilodalton (kDa) region of Plasmodium yoelii merozoite surface protein 1 are induced by the C-terminal 19-kDa region but not by the adjacent 33-kDa region. Ahlborg, N., Ling, I.T., Howard, W., Holder, A.A., Riley, E.M. Infect. Immun. (2002)