A quantitative study of the binding of ALS to various cell types.

The fraction of antibody which bound to the lymphocyte surface, was determined in the [I]IgG preparations of rabbit-anti-mouse ALS prepared by different immunization protocols. This fraction increased with continuing immunization and was higher in sera raised by injection of lymphoid cells in Freund's complete adjuvant (5·3–9·6% of total IgG) than in sera raised by intravenous injection of lymphoid suspension (2·3–5·2% of total IgG). 8·5% of IgG from adjuvant-raised ALS bound to non-lymphoid (liver) cells as compared to 9·6% of IgG which binds to the lymphoid cells themselves. Antibodies against these `species specific' non-lymphoid antigenic determinants were completely absorbed with lymphocyte-free liver cell suspensions. Such absorption did not substantially reduce the immunosuppressive activity of ALS.