Failure of anti-gamma 3 antibodies to detect some gamma3 chains by an agglutination inhibition test.

Four of eight anti-gamma3 antibodies that detect gamma3 by double diffusion were found to test for Gm allotypes when they were used in the agglutination inhibition test. One tested for Gm (26), two for Gm (11), and one for both allotypes. So far as the present data show, the remaining four test for a gamma3 isotype in the agglutination inhibition test. We suggest that a sample that is negative by the agglutination inhibition test should be tested by double diffusion before it is concluded that the sample lacks gamma3.