Myeloma proteins with antiphosphorylcholine activity

Not all BALB/c myeloma proteins with antiphosphorylcholine activity are similar. Some (MOPC 167, MOPC 603) do not share idio-type with other proteins having the same antibody activity and have L chains belonging to unrelated subgroups. The same principle applies to a myeloma protein with mti-Salmonella activity, MOPC 467, whose L chains differ from those of proteins 870 and 384. 

A number of different mouse myeloma proteins [IgA(/f)] have the capacity to bind phosphorylcholine (77,92-94). There is evidence that some of these proteins, which arose independently in different mice, may be very similar or identical in structure. This evidence includes idiotypic specificity and partial sequence analyses (Chapter 11). These proteins also react with pneumococcal type C polysaccharide, which contains haptenic determinants resembling phosphorylcholine. There exist other mouse myeloma proteins which are also reactive with phosphorylcholine but which differ in structure, as shown by differences in their idiotypic determinants, affinities for various haptens related to phosphorylcholine, and partial amino acid sequences. Leon and Young (92) recognized three classes of myeloma proteins with antiphosphorylcholine activity. Class 1 is characterized by a fairly high affinity for choline as well as phosphorylcholine the other two classes do not combine well with choline. Classes 2 and 3 are distinguished by differences in affinity for phosphonocholine. Leon and Young identified four proteins in class 3 all of these had previously been shown by Potter and Liebermann (77)... 

The frequent appearance of mouse myeloma proteins with antiphosphorylcholine or anti-Salmonella activity may possibly be ascribed to antigenic stimulation, resulting in the presence of substantial numbers of cells making antibody with these specificities and subject to malignant transformation. This implies that the transformation can occur subsequent to magnification of the clone after exposure to antigen. 

The Fab fragment of a mouse myeloma protein (number 603) with antiphosphorylcholine activity has been subjected to X-ray crystallography at high resolution (Chapter 5). 

Cosenza and Kohler (47,48) and Sher and Cohn (49) found that antiidiotypic antibodies to the myeloma proteins, TEPC 15 or SI07, which have antipneumococcal (antiphosphorylcholine) activity, almost completely inhibit plaque formation by spleen cells from BALB/c mice immunized with heat-killed strain R36A pneumococci. Erythrocytes used in the plaque-forming tests could be coated either with pneumococcal C-polysaccharide or with phosphorylcholine, with similar results. These significant experiments indicated that nearly all the antibodies produced by BALB/c mice in the primary in vitro response to the pneumococcal polysaccharide shju-e idiotype with a group of mouse... 

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