IgG antibodies to Loxosceles sp. spider venom in human envenoming

The presence and specificity of IgG antibodies produced by patients with loxoscelism were studied. The loxoscelism diagnosis was supported mainly by clinical parameters. A search for IgG antibodies anti-Loxosceles gaucho venom in patients with loxoscelism submitted to serumtherapy showed antibodies in four out of 20 patients. The IgG antibodies were detected as early as 9 days and as late as 120 days after bite. The highest IgG antibody titer was 1:640 and the lowest was 1:80. Immunoblotting tests showed that human anti-L. gaucho IgG antibodies recognize preferentially the components responsible for the dermonecrotic and lethal activities of the venom. A comparison of the clinical picture, the level of serum IgG antibodies and the dose of antivenom administered suggest that there is no relationship between these parameters.