The presence of masked antiribosomal P autoantibodies in healthy children.

OBJECTIVE: To determine if antiribosomal P (anti-P) autoantibodies are present in healthy children.
METHODS: Sera from healthy children were screened for anti-P by conventional enzyme-linked immunosorbent assay and immunoblot techniques. Sera were also treated with immobilized ribosomal P antigens on nitrocellulose strips; affinity-purified fractions were tested for anti-P by high-sensitivity immunoblot. The relative binding affinities were compared for affinity-purified anti-P antibodies from healthy children and adults, and patients with systemic lupus erythematosus. IgG fractions of anti-P-depleted sera from healthy children were assessed for inhibition of autologous anti-P activity.
RESULTS: Conventional serologic screening showed no IgG nor IgM anti-P in 88 untreated sera. IgG anti-P were unmasked in all 79 sera treated by the membrane batch affinity technique. IgM anti-P were identified in 27 of the treated sera; the percentage of positive sera decreased with increasing age (chi(2) for linear trend P = 0.00081). Affinity-purified anti-P from children had relative binding affinities similar to those of anti-P from other groups. Sera from healthy children contained inhibitory IgG antibodies to anti-P.
CONCLUSION: These results show that anti-P autoantibodies are present in all healthy children. The majority of these autoantibodies are masked by IgG antibodies, suggesting concordant development of a regulatory network.