BRUGIA-PAHANGI IN CATS - THE PASSIVE TRANSFER OF ANTI-MICROFILARIAL IMMUNITY FROM IMMUNE TO NONIMMUNE CATS

Serum from cats (Felis catus) that were repeatedly infected with Brugi a pahangi and had become amicrofilaraemic (mf-ve) was injected intrave nously into microfilaraemic (mf+ve) cats. If more than 1 mu l of immun e serum per 1000 mf was injected, microfilarial counts fell dramatical ly within minutes and, in some cats, mf completely disappeared. In mos t cases mf reappeared 21-44 days later. However, in two experiments mf never reappeared and circulating antigen (indicative of the presence of living adults) could not be detected. At autopsy no adult worms wer e found, but in one cat 6 mf/ml were detected by filtration of cardiac blood. Passive transfer of single Ig isotypes showed that IgG is the immunoglobulin responsible for the mf killing effect of immune serum, and that IgGl is probably the most active isotype. Mf killing and dest ruction, occurred in the lungs in an antibody dependent cell mediated reaction involving neutrophils, eosinophils and mononuclear cells. Thr ee of the 20 recipient cats died from what appealed to be anaphylactic shock while under anaesthesia probably due to the sudden release of i nflammatory mediators in the lung.