Effects of presensitization on the development of lymphatic lesions in Brugia pahangi-infected jirds.

Experiments were conducted to measure the degree of lymphatic pathology which develops in mongolian jirds (Meriones unguiculatus) sensitized to Brugia pahangi antigens prior to subcutaneous infections. Two protocols were used to sensitize jirds. One group of animals received three intravenous (IV) inoculations of 5,000 frozen, washed, B. pahangi-microfilariae at 10-day intervals. A second group received three inoculations of 150 micrograms of soluble somatic adult B. pahangi antigen (Ag) in Freund's complete adjuvant (FCA) at 10-day intervals. Groups of animals receiving saline in FCA and animals receiving no treatment served as controls. Following immunizations, animals from each group were tested for circulating antibody by the indirect hemagglutination assay, and for immediate and delayed hypersensitivity responses by the footpad swelling assay. All sensitized animals tested showed positive reaction to these assays. Observations at necropsy 90 days after inoculation with infective larvae showed that: 1) the percent recoveries of adult worms were the same in all treatment groups; 2) the numbers of patent infections which developed in the Ag in FCA-treated animals was greatly reduced; 3) level of microfilaremia which developed in animals sensitized with microfilariae was markedly lower; and 4) the degree of lymphatic pathology as judged by lesion score, numbers of intralymphatic thrombi, and lymphatic vessel size was significantly greater in presensitized animals than in nonsensitized infected controls. The increased lymphatic pathology seen in presensitized animals was most marked in jirds with occult infections and high antibody titers. These observations indicated that the B. pahangi-jird model is a useful semiquantitative system for the study of filarial-associated lymphatic pathology and strongly supports the hypothesis that the host immune response is involved in the pathogenesis of lymphatic filariasis.

Development of Brugia pahangi infections and lymphatic lesions in male offspring of female jirds with homologous infections.

The development of Brugia pahangi infections and associated gross lymphatic lesions were compared in male offspring from B. pahangi-infected and uninfected female jirds. The numbers of adult worms recovered did not differ between groups but a greater number of offspring of infected females (92%) developed circulating microfilaraemias than did individuals from uninfected females (50%). Intralymphatic granulomatous thrombi, lymphatic dilatations and lymphatic lesion scores were significantly reduced in offspring from infected mothers.

Specific hypo-responsive granulomatous tissue reactions in Brugia pahangi-infected jirds.

Two types of experiments were used to study the degree of tissue responsiveness which occurred in Brugia pahangi-infected jirds. In experiment 1, the severity of lymphatic lesions which developed following subcutaneous infection of jirds which has existing intraperitoneal infections was compared to the severity of lymphatic lesions that developed following subcutaneous infection of jirds without previous infections. In experiment 2, comparisons were made of the sizes of granulomas which formed in the lungs around cyanogen bromide-activated Sepharose 4B beads coupled with B. pahangi antigen, which were inoculated intravenously into jirds which: 1. had existing lymphatic infections; 2. were uninfected. Results of both experiments indicated that jirds with intraperitoneal or lymphatic infections of B. pahangi of 120 to 160 days duration were significantly less responsive to B. pahangi or B. pahangi antigens as measured by pathologic tissue reactions than were uninfected jirds. The sizes of granulomas which formed around beads coupled to B. pahangi antigen in noninfected and nonsensitized jirds suggest that this worm material may contain factors which nonspecifically enhance the granulomatous inflammatory reaction.

Equine alternative pathway activation by unsensitized rabbit red blood cells.

The equine alternative complement pathway has been partially characterized and compared to the equine classical activation pathway. A dose-dependent lysis of RbRBC was observed with peak lytic values noted within 10 minutes at 37 degrees C when rabbit red blood cells (RbRBC) were used as an alternative pathway activator. Sheep red blood cells (SRBC) sensitized with rabbit hemolysin or partially purified equine IgM antibodies were equally sensitive to lysis. Dilution of the commercial hemolysin by 1/5 reduced lysis from 90% to 38% in the presence of constant cell numbers. Hemolysis of SRBC peaked at 10 minutes and the majority of lysis occurred within 10 minutes. Dilution of equine sera by as little as 1/5 decreased hemolytic activity for SRBC to 21.5% from greater than 90% with undiluted sera. The alternative pathway protein, equine factor B, was tested using RbRBC and monitored by its differential susceptibility to heat treatment at 50 degrees C. This treatment led to almost complete inactivation after a 15-minute incubation. An apparent heat-dependent decay of certain classical pathway components was also observed after 50 degrees C treatment. This sensitivity was indicated by a reduction in the lytic activity for sensitized SRBC. Treatment for 15 minutes at 56 degrees C with either RbRBC or SRBC was sufficient to abolish hemolytic activity in all equine sera tested. Chelation of cations with 0.04 M EDTA blocked expression of alternative and classical pathway activation; however, chelation of Ca++ ions with 10 mM EGTA containing 1 mM Mg++ ions permitted lysis of the RbRBC but not the SRBC. A dose-related Mg++-ion dependence for RbRBC hemolytic activity was observed as the concentration of Mg++ was increased to 1.0 mM. In addition, our results obtained with pre-colostral foal serum strongly suggest that natural antibody to RbRBC was of little importance in the lysis observed with these cells. These results also show that the equine alternative pathway activation may require Ca++ ions. If Ca++ ions are required, the equine alternative pathway is quite different from any other mammalian complement system so far described. Our results suggest that the alternative pathway of activation is of major importance in the equine complement system. Confirmation of this hypothesis requires both purification of the components involved as well as further characterization.