Immunological studies of the anticryptococcal factor of normal human serum

Preliminary studies have shown a very high inhibitory activity in the alpha2 and gamma zone of human serum towards the growth of Cryptococcus neoformans. These findings are now corroborated by single radial immunodiffusion tests, which showed the some loss of IgA and IgM globulins and of the other three globulin fractions (ceruloplasmin, alpha2 macroglobulin and alpha2 HS glycoprotein) which migrate in the alpha2 zone. The data was obtained by single radial immunodiffusion tests. The losses were not statistically significant however. No change in the immunoglobulin content of the sera kept for 6 days in contact with a heat-killed suspension of C. neoformans was noted. These findings suggest, that the inhibitory activity of the normal human serum on the in-vitro growth of C. neoformans is due to the above mentioned globulin fractions and not to a single specific factor.