Serological characterization of γM (19 S) and γG (7 S) rabbit antibodies in response to Entamoeba histolytica antigens

Abstract

Entamoeba histolytica (DKB strain) antigen mixed with an equal volume of complete Freund's adjuvant was injected at multiple sites into three rabbits. Primary response sera were drawn 1, 2, and 3 weeks after the first injection. Two injections of antigen were given in the fourth week, at 3-day intervals. The secondary response sera were drawn 5, 6, and 12 weeks after the beginning of immunization. A steady hemagglutination (HA) titer of 1:128 was obtained with all the three primary response sera, while the secondary response sera showed HA titers of 1:2000 to 1:8000. The 0.1 M 2-mercaptoethanol treatment of these sera reduced, but did not completely obliterate, their HA activity. The HA activity was detected in both the pooled γM and γG classes of immunoglobulins of the primary and secondary response sera; the immunoprecipitating activity was confined to the γG class. 2-Mercaptoethanol treatment completely destroyed the antibody activity of γM fractions without affecting that of the γG fraction. Repeated immunoelectrophoresis runs of the whole sera and pooled γM and γG fractions showed variable numbers of precipitin bands at the γG position but none at the γM and γA positions.