Persons exposed to Onchocerca volvulus express differences in manifest
ations of onchocerciasis ranging from hyporeactive (generalized) to hy
perreactive (sowdah) forms; absence of disease is seen in endemic norm
al persons. Analysis of the IgG isotypic antibody response to O. volvu
lus extracts and nonparasite ubiquitous antigens in 92 West Africans r
evealed highest anti-O. volvulus IgG1 and IgG2 responses in sowdah, hi
gh levels in the generalized form, and low antibody levels in endemic
normal persons. Nonexposed persons had no antibodies. A significant Ig
G3 antibody response was detected only in sowdah, while high IgG4 leve
ls occurred in both polar groups but were absent in both control group
s. Isotypic responses to antigens unrelated to O. volvulus were simila
r in all groups but showed higher IgG1 and IgG2 levels in sowdah. Sowd
ah patients had high levels of Ro/SS-A antibodies, circulating immune
complexes, and eosinophil cationic protein. These results document a s
trong B cell response in African sowdah and indicate variations in imm
une responsiveness.