Microfilariae of Brugia pahangi in the Blood of Cats Have Variable Levels of Feline IgG on Their Sheaths

r: Feline IgG was found on the sheath of microfilariae (mf) of Brugia pahangi isolated from the blood of cats. Gamma heavy chains, both light chains, and the Fc and F(ab')2 portions of IgG were present, suggesting that the molecule is intact. The amount of IgG on the sheath was variable and the younger the mf the less IgG was present on their sheaths. Possible functions of this adherent layer of host protein are considered. Microfilariae (mf) survive in the circulation of mammals despite the production of antibodies that recognize their interior metabolic or surface antigens. This suggests that they have some mechanism for evading immune attack. It is possible that they adsorb some host factor that shields susceptible sites from immune attack. Using affinity-purified anti-cat Ig reagents and mouse anticat Ig monoclonal antibodies (Mab) we have demonstrated feline immunoglobulin on the surface of mf of Brugia pahangi isolated from the blood of infected cats. Rabbits were immunized (Parkhouse and Askonas, 1969) with cat IgG that had been adsorbed from normal cat serum onto protein-Asepharose (Pharmacia), eluted with 0.2 M glycine-HCl at pH 2.8, neutralized with solid tris, and dialyzed against 0.15 M NaCl. Rabbit anticat IgG antiserum was passed through cat IgGsepharose columns, and anti-cat IgG antibody was eluted as above. Cat IgG was converted to F(ab')2 by digestion with pepsin (0.2 M NaAc, pepsin 2% w/w of IgG for 16 hr, 37 C at pH 4.2) and rabbits were immunized. Their antibodies were affinity purified by adsorption onto a column of cat IgG-sepharose followed by elution as above. Anti-cat Fc was collected in the unbound fraction obtained when purified rabbit anti-cat IgG was passed through a column of cat F(ab')2-sepharose. All the affinity-purified rabbit anti-cat reagents were conjugated with fluorescein isothiocyanate (FITC). Mouse Mab to cat mu chains (CC4), gamma chains (ACS), kappa light chains (BA3), and lambda light chains (EA2) were donated by Drs. F. Klotz and M. D. Cooper (University of AlaThis content downloaded from 207.46.13.145 on Sun, 03 Jul 2016 04:33:31 UTC All use subject to http://about.jstor.org/terms