SOLUBLE ANTIGEN FLUORESCENT-ANTIBODY TECHNIQUE.

An indirect fluorescent-antibody (FA) procedure employing soluble antigen fixed onto an artificial matrix was developed, and a mechanical means for reading of test results was devised. The method employs two small cellulose acetate paper discs for each test. One disc contains soluble antigen diluted in 1% bovine serum albumin (BSA); the other contains only 1% BSA and serves as a control. After testing by the indirect FA procedure, the results of the tests are read on a fluorometer fitted with a paper chromatogram door. The instrument is set at zero with the control disc as a blank, and the specific fluorescence of the antigen disc is determined. Findings obtained with homologous and heterologous antisera indicated that the method yields excellent results. The soluble antigen fluorescent-antibody technique has definite advantages over the conventional indirect FA procedures. (i) The investigator may objectively select the antigen to be employed. (ii) It is possible to obtain objective mechanical reading of test results rather than the highly subjective readings required by conventional methods. (iii) The system compensates for any nonspecific fluorescence contributed either by the serum (e.g., drugs) or by free fluorescein in the conjugated antiserum.