Antibodies to germinating and yeast cells of Candida albicans in human and rabbit sera.

Two major antigenic components, I and II, were detected by double immunodiffusion in sonic extracts of the germinating (G) or yeast (Y) cells of the dimorphis organism, Candida albicans group A. Component I may be a heterogeneous mixture of antigens which are stable to heating and phenol. Component II is more homogeneous but is labile to heat and phenol. Rabbit antisera, showing only precipitin to component II or certain human sera at high dilution, were found to react with G cells to give an immunofluorescence which was confined to the germ tubes. This suggested that component II is localised on the germ tubes, whereas no immunofluorescent reaction against the yeast cells could be detected under the same conditions although component II was as readily extracted from these cells as from G cells. This suggested that component II might exist in a cryptic state in the Y cells. In support of the latter contention it was shown that live Y cells did not absorb precipitin to component II nor were they capable of providing these antibodies in rabbits. Using both human and rabbit sera, it was shown that the antigenic specificity of the immunofluorescence assay where Y cells were used was related to component I and that where G cells were used it was related to both components I and II.