SPECIFICITY OF ANTI-GLOBULIN FACTORS IN HUMAN SERA

Fifteen sera showing antiglobulin activity non-neutralizible by human γ-globulin, were found by screening with anti-D coated red cells, and characterized as follows:1) Only two out of fifteen sera exhibited no selectivity to various anti-D coated cells and can be included into “anti-antibody” defined by Milgrom. Remaining sera showed more or less selective reactivity either related or unrelated to allotypes of anti-D sera used.2) Red cells sensitized with human anti-bodies other than anti-D or merely coated with human γ-globulin were not agglutinated, or very weakly agglutinated by these sera.3) The antiglobulin activity of some of the sera was found to be neutralized, at least partially, by heat-treated human γ-globulin or by native rabbit γ-globulin.4) Antiglobulin activity to anti-D coated cells was considerably removed even by absorption with anti-D coated cells or with other sensitized cells which did not show strong agglutination by these sera.5) Agglutination titers of anti-D coated red cells and of sensitized sheep red cells were affected by absorption by homologous as well as by heterologous sensitized red cells.From the above results, it can be seen that the antiglobulin factor in these sera is non-neutralizible by syngeneic γ-globulin, yet cross-reacting to xenogeneic antibody.Antiglobulin activity to anti-D coated red cells in rheumatoid arthritis (R. A.) sera, on the contrary, can be analyzed into factors with single allotype specificity py absorption or neutralization procedures, and seems different from the non-neutralizible factor in this respect.