NEUTRALIZATION OF BOTHROPIC AND CROTALIC VENOM TOXIC ACTIVITIES BY IGG(T) AND IGGA SUBCLASSES ISOLATED FROM IMMUNE HORSE SERUM

IgG(T) and IgGa isotypes were isolated from horse hyperimmune anti-bot hropic and anti-crotalic sera using a combination of two affinity chro matographic processes, IgG(T) and IgGa isotypes were isolated from the se sera by chromatography on protein A-Sepharose followed by separatio n of the two isotypes by chromatography on a column of anti-IgG(T)-Sep harose. LO-HoGT-1, a rat anti-horse IgG(T) monoclonal antibody, was us ed. A comparative study of the efficiency of these isotypes in neutral izing the main toxic activities of the homologous venoms was carried o ut. It was found that IgG(T) was about three-fold and seven-fold more protective than IgGa for neutralization of the lethal activity of B, j araraca and C.d. terrificus venoms, respectively. IgG(T) was also more effective than IgGa for the neutralization of the haemorrhagic activi ty induced by B. jararaca venom, while both isotypes neutralized equal ly well the blood incoagulability induced by this venom. The results s uggest that IgG(T) is the most protective isotype present in both anti -bothropic and anti-crotalic sera, followed by IgGa. Owing to their ve ry low concentration in the serum, other IgG isotypes are not likely t o be important in neutralizing the venoms' toxic activities. (C) 1997 Elsevier Science Ltd.