Properdin system in host resistance

Under carefully controlled conditions, bovine serum properdin was isolated and partially purified by employing cold ethanol fractionation procedures. The euglobulin was recovered in the serum fraction which was insoluble at pH 6.9, -5° and at a final ethanol concentration of 20 percent v/v. The partially purified bovine properdin and purified human properdin were employed as therapeutic agents against the effects of ionizing ration in whole body x-irradiated mice and rats. No protection was observed when the solutions were administered intraperitoneally or intravenously; however, there appeared to be a relationship between delayed mortality and post-irradiation time of injection. Under the experimental conditions employed, post-irradiation administration of cell-free mouse splenic extract to whole body x-irradiated mice (intraperitoneally) and guinea pigs (intramuscularly) did not result in protection against post-irradiation death. The treated animals died at an accelerated rate when compared to the controls. In vivo experiments could not elucidate the role of the properdin system in host resistance; therefore, in vitro techniques for investigating the effect of properdin on phagocytes were conducted. Yeast phase Histoplasma capsulatum cells labeled with P-32 were used in a series of experiments to study the effects of humoral factors on the in vitro ingestive and digestive activities of phagocytes obtained from normal and immunized mice. Among humoral factors studied by this technique were complement, properdin and antibody. In all cases, a heat-labile component (complement and/or properdin) not only enhance phagocytic rates by normal and "immune" phagocytes, but caused a significant enhancement of the digestive activities of the "immune" cells as compared to the normal phagocytes. Specific antibody does not appear to play any significant role in phagocytic or cytopeptric activities of normal of "immune" phagocytes when a chronic digest agent, H. capsulatum is used as the P-32 labeled organism.