STUDIES ON THE COMPLEMENT FIXATION TEST WITH MYCOPLASMA PNEUMONIAE ANTIGEN

M. pneumoniae cell suspensions prepared by 4 different techniques were examined with regard to the degree of contamination with broth medium constituents, using quantitative protein measurements and gel diffusion tests with antisera against broth medium constituents. Unwashed pellets from high‐speed centrifugation of broth cultures were found to be highly impure. Washing the pellets by repeated resuspensions and centrifugations resulted in an only partial purification, broth medium constituents precipitated as a result of the centrifugation being largely unremovable by this procedure. Prefiltration of the broth medium yielded less contaminated, but still impure, pellet antigens. Suspensions prepared by scraping off washed layers of M. pneumoniae grown on a plastic surface did not show gel precipitation reactions of broth medium constituents; their protein figures were relatively high. The significance of this finding is discussed. The yields from cultures on plastic surfaces were found to be greatly increased by a renewa of the broth medium during the incubation period. A filter disc method for harvesting . pneumoniae cells from broth cultures is described, the cells being washed upon, and thereafter scraped off from, the surface of Millipore filter discs type GS (0.22 μ). This method yielded cell antigens of significantly higher purity than the centrifugation method. The filter disc method, in combination with prefiltration of the broth medium, is easily practicable for harvesting washed cell suspensions of broth‐grown M. pneumoniae for experimental studies and the production of diagnostic antigens.