Western blot analysis of IgG subclass responses. Asexual blood-stage F32 parasite proteins (PEMS preparation, 100 μg) were separated by SDS-PAGE and blotted onto nitrocellulose membranes. Membranes were cut in vertical strips, blocked and incubated with individual plasma from A) Danish travelers who have suffered a single episode of P. falciparum malaria (n = 7), B) Ghanaian children age 0-5 (n = 8), C) Ghanaian children age 6-10 (n = 6), and D) clinically immune Liberian adults (n = 12). Antibody responses were revealed with monoclonal antibodies directed to human IgG1, IgG2, IgG3, IgG4 and IgM and visualized with AP-conjugated anti-mouse antibodies. For each of the different groups (A to D) reactivity of two representative individual plasma samples are shown, where the one to the left was seen to have high IgG titers determined by ELISA against late-stage parasite extract, whereas the one to the right had low IgG titers in the same assay. Western blots were performed with different SDS-PAGE gels, all loaded with the same protein preparation (100 μg) and run under identical electrophoretic parameters. The strips shown originate from a single blot.