Familial resemblance in humoral immune response to defined and crude Schistosoma mansoni antigens in an endemic area in Brazil

This study addressed whether the humoral immune response to crude and defin ed Schistosoma mansoni antigens aggregates within families. The sample incl uded 155 siblings from 42 nuclear families in Brazil. Sera examined by ELIS A for antibody isotypes reactive to defined schistosome antigens and crude schistosome antigens (soluble adult worm antigen preparation and soluble eg g antigen) demonstrated that there was a difference in sibling-pair correla tions between defined and crude S. mansoni antigens. In contrast to the fin ding with crude antigens, egg-positive sibling pairs showed significant fam ilial resemblance for all IgG subclasses and IgE to adult-stage antigens Sm p20.8 and Smp50. Only the IgE and IgG4 isotypes showed familial resemblance to the egg-stage antigen, Smp40, Egg-negative sibling pairs showed signifi cant familial resemblance only for IgE and IgG4 to Smp40. That both the IgE and IgG4 response to defined S, mansoni antigens showed familial resemblan ce is interesting in light of the converging evidence for the role of IgE a nd IgG4 in human susceptibility and resistance to reinfection.