Precipitin reaction, quantitative cross-reactions

The immunochemical cross-reactivity revealed by quantitative precipitin reaction of 22 primate serum albumins with anti-HSA was consistent with the presumed phylogenetic relationships to man on the assumption that the evolutionary modification of protein structure has been... 

GSA. A high proportion of anti-BSA—151%—was adsorbed by ESA immunoadsorbent, 66.4% by Sepharose-PSA, and 39% by Sepharose-HSA. The cross-reacting antibodies were found to precipitate more with BSA than with the homologous albumin that is in the immunoadsorbent. The high cross-reactivity shown by immunoadsorbent is the result of the presence of high proportions of nonprecipitating antibodies which es-c q>ed detection in the quantitative precipitin reaction and were trapped by the immunoadsorbent. Therefore, in determination of cross-reactivity, special precaution has to be exercised to account for the presence of nonprecipitating antibodies. 

The quantitative precipitin method presupposes availability of fairly pure antigens and the successful production of specific antisera free of antibodies to contaminant proteins. Immunochemical techniques are available to ascertain whether or not these criteria have been fulfilled. Nevertheless, the possibility of cross-reactions of specific antibodies with other closely related antigens must be considered a limitation of the method. 

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