Myeloma precipitin reaction

Percent Inhibition of Glucosyl Compounds for the Myeloma Protein and Precipitin Reaction... 

Kabat (251) was able to show by immunochemical methods that the main component of the serum of case 11 (Table VII) was, in fact, a Bence-Jones protein. Rabbit antiserum to this patient s urinary Bence-Jones protein gave a strong precipitin reaction with a 1 625 dilution of the patient s serum. This reaction appeared to be due entirely to Bence-Jones protein since after absorption of the rabbit antiserum with case 11 myeloma serum no additional precipitin reaction could be obtained with the patient s urine or purified Bence-Jones protein nor did the (absorbed) antiserum react with normal serum protein constituents. Qualitative dilution tests indicated a concentration of Bence-Jones protein in the serum of the same order of magnitude as was obtained for the main abnormal component by other methods. In case 1 (Table VII) Kabat was also able to demonstrate by immunochemical methods that while the main component was not a Bence-Jones protein, 0.15 to 0.2 gram per cent of a Bence-Jones protein nevertheless was present and could be identified and estimated by emplojdng the quantitative precipitin method. This concentration, approximately 1.5% of the total protein content of this serum, obviously could not be detected by salting-out, electrophoretic, or ultracentrifugal methods. 

Quite different results have been obtained when cross-reactions were investigated by inhibition of specific precipitation. In several systems nonspecific IgG inhibited, partially or completely, the precipitation in liquid medium of human IgG myeloma proteins by rabbit anti-D antisera classical precipitin tests were utilized (18,97). 

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