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Immunological unresponsiveness induced by cryptococcal capsular polysaccharide assayed by the hemolytic plaque
Abstract:
Numerous studies have suggested that cryptococcal capsular polysaccharide could induce an immunological paralysis. To investigate this possibility, mice were given various concentrations of purified cryptococcal polysaccharide and then 14 days later were challenge-immunized with the same material in Freund's incomplete adjuvant. Anticryptococcal agglutinin titers were determined at various periods after polysaccharide treatment and after challenge immunization. At the same periods the hemolytic plaque technique was used to determine the number of spleen cells capable of producing antibody against cryptococcal polysaccharide. The data indicated that there was a transitory immune response which preceded tolerance induction. In animals given the largest doses of polysaccharide, "in vivo" neutralization was responsible for low serum agglutinin titers during the transitory response. The capsular polysaccharide was considered to have induced immunological unresponsiveness at the highest concentration, because challenge immunization did not stimulate an increase in the number of plaque-forming cells (PFC). A sixfold increase in numbers of PFC was found in animals injected initially with the lowest concentration of polysaccharide. These results support the idea that tolerance was due to terminal differentiation without proliferation of the immunocompetent cells. The central failure of the immune mechanism which was apparent in the paralyzed mice was temporary under the conditions of this experiment.
Insights
Cryptococcal polysaccharide can induce temporary immune tolerance in mice. High doses lead to unresponsiveness, while lower doses initially boost antibody production before tolerance develops.
Area of Science:
- Immunology
- Microbiology
Background:
- Cryptococcal capsular polysaccharide is suspected to cause immunological paralysis.
- Understanding this phenomenon is crucial for developing effective immune interventions.
Purpose of the Study:
- To investigate the potential of cryptococcal capsular polysaccharide to induce immunological paralysis in a murine model.
- To characterize the immune response following polysaccharide administration and subsequent challenge immunization.
Main Methods:
- Mice were administered varying concentrations of purified cryptococcal polysaccharide.
- Mice were subsequently challenge-immunized with the polysaccharide in Freund's incomplete adjuvant.
- Anticryptococcal agglutinin titers and plaque-forming cells (PFCs) were measured.
Main Results:
- A transient immune response was observed, preceding tolerance induction.
- High polysaccharide doses resulted in immunological unresponsiveness, with no increase in PFCs upon challenge.
- Lower doses initially increased PFCs, suggesting a dose-dependent tolerance induction mechanism.
Conclusions:
- Cryptococcal capsular polysaccharide can induce temporary immunological unresponsiveness.
- Tolerance appears to result from terminal differentiation without proliferation of immunocompetent cells.
- The observed immune paralysis is temporary under experimental conditions.