A quantitative micro-complement fixation test capable of detecting nanogram quantities of antigen is described. The test is simple to perform and is highly reproducible. Typical results from three antigen-antibody systems are given.

Antinuclear antibodies were detected by immunofluorescence in most sera from rabbits immunized with whole human serum emulsified in Freund's complete adjuvant. Four of 14 sera from rabbits immunized with Cohn fractions III, IV-1, or IV-4 also gave positive nuclear fluorescence with human leukocyte nuclei. Other human and animal nuclei gave negative results with these rabbit antisera. Three rabb...