Reactivity in ELISA of sera from lupus mothers of groups I and II with Ro antigens. Sera were classified into three subgroups: (a), (d) before, (b), (e) during, and (c), (f) after pregnancy. The results are expressed in terms of frequency (%) of positive reaction ((a)–(c)) and antibody level (mean optical density [OD] values + standard deviation) ((d)–(f)). Mothers' sera were tested at a 1:1,000 dilution and the IgG response only was evaluated. The number of samples (number of mothers) was as follows; group I (black bars): (a)–(d), 5 (3); (b)–(e), 8 (5); (c)–(f), 6 (5); group II (white bars): (a)–(d), 18 (4); (b)–(e), 44 (16); (c)–(f), 12 (7). All samples were systematically tested in at least two independent tests. The results shown in the figure correspond to one complete representative experiment. The sera were considered positive when OD ≥0.3 (visualized by a longitudinal lane in panels (d)–(f)). All sera were tested with the 48 antigens. Only the Ro antigens showing reactivity are depicted. For clarity, the first residue of each peptide sequence is indicated in the figures (107-1 for 107–122; 107-2 for 107–126). (a)–(c) Student's t test, *0.05 > P > 0.01, **P ≤ 0.01; (d) and (e) Mann-Whitney U test, *0.05 > P > 0.005, **P ≤ 0.005.