IEs adhering to the antibody-coated beads were isolated in a strong magnetic field and subsequently returned to in vitro culture. Selection protocol was repeated when multiplication of the antibody-selected parasites allowed it. VSA expression was assessed by flow cytometry analysis as described elsewhere (8) . We used plasma from 10 P. falciparum -exposed multigravidae, 10 sympatric men, and 10 nonexposed controls to assess the sex-specificity of VSA recognition. According to the original criteria (9), sex-specific recognition requires that (i) levels of IE-surface reactive IgG are significantly higher in P. falciparum -exposed multigravidae than in sympatric men, and that (ii) the difference in IgG levels in P. falciparumexposed men and nonexposed controls is not statistically significant. We used term plasma from 30 P. falciparum -exposed women (10 pregnant for the first time, 10 for the third time, and 10 for the fifth time) to assess parity-dependency, which requires a statistically significant relationship between IgG levels and number of pregnancies in P. falciparumexposed women (9) . Parasite isolates were only considered to express VSA PAM if plasma IgG recognition of IEs was both sex-specific and parity-dependent.