The Antigenic Relationships of Native Antigens of Species of Brucella

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Abstract
Summary: The serologic reactions between phenol-extracted antigens of Brucella and their antisera have been studied by the quantitative precipitin reactions. The curves of the amount of total nitrogen precipitated when plotted against the antigen nitrogen added showed a series of two or more maxima as the amount of antigen was increased. It was suggested that these secondary rises were indications of reactions between minor antigen-antibody systems. The absorption of anti-melitensis serum with a rough strain of either Br. abortus or Br. melitensis eliminated the secondary rises. Throughout the entire range of the reactions an antibody excess has been shown affording further evidence of the mixed nature of the antigens. The ratios, antibody nitrogen/antigen nitrogen, of the precipitates were lower for the suis system than with the other systems at the point of maximum precipitation. The similarity of the reaction curves and the ability of heterologous antigens to remove more precipitins from an antiserum than the homologous antigen, suggested a close relationship between the fractions obtained from the three species. This relationship may be an expression of a common group antigen such as that attributed to the rough component of the cell, or to other still unknown antigenic components. Although the course of the reactions reported here did not follow the linear relationship for pure systems as developed by Heidelberger and Kendall, it appeared that the homologous systems would show a linear relationship between precipitate ratios and antigen added for the first three and four points. Heterologous systems did not and would not be expected to do so.