Immunofluorescence and SPR analysis. (A) Immunofluorescence patterns of Abs or diabodies reactive with MSP1₁₉ on methanol-acetone-fixed smears of merozoites and erythrocytes infected with P yoelii YM. The smears were incubated with human IgG1 (iii,iv), human IgA1 (v,vi) and the FcγRI × MSP1₁₉ diabody (ii). No specific fluorescence was detected with an irrelevant FITC-labeled Ab (i) or with the secondary F(ab′)₂ anti-Ig Ab alone (not shown). Original magnification: panels i-iii, v, × 40; iv, vi, × 100. (B) SPR association and dissociation curves of Ab binding to MSP1₁₉ immobilized on a CM5 sensor chip. Abs were injected into flow at time 0, and replaced with buffer at the points indicated by vertical arrows.