IgG Levels and Host Specificity in Hydatid Cyst Fluid

Abstract

IgG was found in sheep hydatid fluid at concentrations ranging between 1 and 3 Aug/ml by the specific radial immunodiffusion method. The species-specific antigenic determinants of the host immunoglobulins were found in hydatid cyst fluid from 4 different species of hosts. The albumin levels and albumin/IgG ratios of cyst fluid were also determined. It is postulated that these proteins enter the parasite by diffusion from the surrounding host tissues. Host serum protein components have been demonstrated in hydatid cyst fluid and attempts made to quantify them. Codounis and Polydorides (1936) detected albumin concentrations of 80 to 1,200 /ug/ml in human hydatid fluid (HHF). In studies with paper electrophoresis Magath (1959) reported a total protein concentration of 75 [g/ml in HHF, of which 33 /g/ml were in the albumin region and 13.5 1tg/ml in the gamma globulins. Goodchild and Kagan (1961) observed variations in the concentrations of protein in the albumin and gamma globulin regions of the cyst fluids of Echinococcus granulosus and E. multilocularis using paper and starch electrophoresis. They also found differences between cysts of E. granulosus from different host species. Chordi and Kagan (1965) identified and characterized 10 bands of parasite origin in sheep hydatid fluid (SHF) by means of immunoelectrophoresis. Nine other bands were common to host serum and of these albumin and gamma globulin were the major components. From an examination of the electrophoretic patterns reported by these authors it is clear that some parasite antigens in SHF also have electrophoretic mobilities in the albumin and gamma globulin regions. This suggested to us that measurements of their quantities of host albumin and gamma globulin in hydatid fluid by electrophoretic methods does not provide an accurate account of the levels of those components which are truly of host origin. This report concerns the results obtained using radial immunodiffusion as a specific method for determining the levels of host Received for publication 2 December 1971. albumin and immunoglobulin in sheep hydatid fluid. The species specificity of the immunoglobulins in the hydatid fluid obtained from cysts in different hosts was also investigated. MATERIALS AND METHODS Radial immunodiffusion was performed according to the method of Mancini et al. (1965) and immunoelectrophoresis by that of Scheidegger (1955). Rabbit anti-sheep IgG serum IgG was purified from the whole sheep serum by precipitation with 33% saturated ammonium sulfate followed by dialysis against 0.005 M phosphate buffer pH 8 and separation in a DEAEcellulose column, stabilized with the same buffer. The ascending portion of the first eluted peak was used to immunize rabbits. Each animal was inoculated intramuscularly with 300 uug of purified IgG in Freund's complete adjuvant, weekly for 5 weeks. In immunoelectrophoretic tests using normal sheep serum this rabbit antiserum detected a single band in the IgG region.