A quantitative immunofluorescence test for the detection of anti-Candida antibodies.

A quantitative immunofluorescence assay for anti-Candida antibodies has been developed using a recently introduced system that includes an automatic fluorometer and a special immunoadsorbent for antigen coating. A commercially available cytoplasmic antigen preparation was adsorbed into the substrate, and after incubation with sera from patients with systemic candidiasis or from normal controls, the antibodies bound to the antigen-coated immunoadsorbent were revealed by the use of fluorescein-labeled antisera to human immunoglobulins. Using doubling dilutions of a high titer serum, a positive relation was found between antibody concentration and the logarithm of the intensity of fluorescence. Quantitative assays of unknown samples were performed using a calibration curve constructed from dilutions of that strongly positive sample; the results of antibody determinations were expressed as percentages of the control. Seven of 9 sera from patients with systemic candidiasis, and only 2 of 42 from asymptomatic individuals, had antibody levels considered significant in this assay. Precipitating antibodies were detected by counterimmunoelectrophoresis in all patients and in 18 of the asymptomatic controls; measurable antibody levels were also found in 14 controls showing no precipitating antibodies. This assay is simple, sensitive and inexpensive, and its quantitative nature makes it useful in the investigation of the immune response to C. albicans.