Classification of blood-group antibodies as beta2M or gamma globulin

Abstract

Thirty selected blood-group antibodies (excluding anti-A and anti-B) have been classified as β₂M (19S γ) globulin, γ (7S γ) globulin or mixtures, using the following three methods: fractionation on a DEAE-cellulose column; indirect anti-globulin tests, using specific anti-β₂M-globulin and anti-γ-globulin sera; and treatment with 2-mercapto-ethanol. With only minor exceptions, results obtained with the three methods were in agreement.

Most blood-group antibodies within the Le, MNSs and P systems appear to be `naturally occurring' and these were found to be β₂M globulin. Blood-group antibodies within the Rh, K and Jk systems, which had arisen after an antigenic stimulus, were usually γ globulin but were occasionally β₂M globulin.

Antibodies composed of β₂M globulin usually behave as agglutinins but may behave as incomplete antibodies (e.g. some examples of anti-Jk^a); conversely, antibodies composed of γ globulin usually behave as incomplete antibodies but may behave as agglutinins (e.g. an example of anti-M).

The ability to bind complement seems to be related more to the blood-group specificity of the particular antibody than to its molecular size. For example, anti-Jk^a, when composed either of γ or β₂M globulin, seems invariably to bind complement, whereas potent anti-M or anti-Rh, whether composed of γ or β₂M globulin, do not bind complement.