Quantitative Studies on Reverse Cutaneous Anaphylaxis in Mice with Progressive Cryptococcosis

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Abstract
Summary: Intradermal injections of C. neoformans rabbit antibody specifically provoked cutaneous anaphylactic reactions in mice with active experimental cryptococcosis as well as in uninfected animals previously prepared by passive administration of purified cryptococcal polysaccharides. In general, passive anaphylaxis tests in mice with this fungal system were more sensitive (interms of Ab N required for reactions) than tests reported with other antigen-antibody systems and in guinea pigs, sensitivity was either the same or somewhat less than with other systems. RCA tests became positive in mice after an initial lag period of 4 to 6 days following infection with C. neoformans and thereafter the intensity of the reactions, as measured by intradermal titrations with antibody, increased with time as the disease progressed. A direct correlation was demonstrated between fungus cell count in the brain and sensitivity of antemortem reverse cutaneous anaphylaxis (RCA) titrations. Absorption of C. neoformans antiserum with cryptococcal polysaccharide abolished its capacity to provoke reactions in infected mice. Intravenous injection of 0.1 mg Ab N resulted in severe or fatal anaphylaxis in mice that were infected 15 days prior to the test. The possible application of the antiserum intradermal test to the study of human cryptococcosis is suggested.