Ability of CBA Mice to produce Anti-idiotypic Sera to 5563 Myeloma Protein

Abstract

MICE can produce isoantibodies against immunoglobulins which carry allotypic determinants not present on their own immunoglobulin. For instance, the plasmacytoma 5563 (a _γG_2a protein) arose spontaneously in C3H mice and expresses the Ig-l^a locus like normal immunoglobulin of this class in this strain. C57B1/6 mice whose _γG_2a molecules express the Ig-l^b locus can produce antibodies reacting with Ig-l^a determinants, if they are injected with 5563 myeloma protein in a suitably immunogenic form; but CBA mice cannot. The Ig-l locus is expressed on the constant region within the Fc fragment¹. It has been found that mice producing antibodies against these determinants also produce antibodies against idiotypic—myeloma specific—determinants located within the Fab fragment². Mice immunized with non-conjugated myeloma protein either produce antibodies against both allotypic and idiotypic specificities or they produce nothing against either determinant. Thus mice cannot detect idiotypic determinants on non-conjugated myeloma protein with allotypic determinants that their own immunoglobulins possess. Cohn et al.³ have suggested that the Fc portion of the molecule acts as a “carrier” for the Fab portion, in the sense that an otherwise noii-immunogenic determinant (the “hapten”) becomes immunogenic if attached to a structure which is itself immunogenic (the “carrier”). It has been shown that the “carrier effect” of Ovary and Benacerraf⁴ increases the immune response to the “hapten equivalent” by virtue of antigen-mediated cell cooperation^5,6.