Variable Levels of Host Immunoglobulin on Microfilariae of Brugia Pahangi Isolated from the Blood of Cats

Using a variety of polyclonal affinity purified antibodies and monoclonal antibodies against humoral components of cat serum we have demonstrated cat IgG on the microfilarial sheath of Brugia pahangi isolated from the blood of cats. No feline IgG could be seen on microfilariae born to pregnant adult female worms maintained in vitro, nor on the surface of microfilariae whose sheaths had been removed. Microfilariae are born without IgG on their sheaths and slowly accumulate it as they circulate in the blood. This process results in variable levels of host immunoglobulin on the microfilariae. It is not known whether the IgG protects the worm from recognition by the host or that it eventually accumulates to such a level that it mediates killing of the worm by granulocytes.