An IgM Waldenström with specificity against phosphorylcholine

Area of Science:

• Immunology
• Biochemistry

Background:

• Anti-phosphorylcholine specificity is common in mouse IgA myeloma proteins.
• This specificity is rare in human myeloma proteins.

Purpose of the Study:

• To investigate the incidence and characteristics of anti-phosphorylcholine antibodies in human myeloma sera.

Main Methods:

• Screening of 904 human myeloma sera.
• Isolation of active protein using affinity chromatography (Sepharose-phosphorylcholine immunoadsorbent).
• Characterization of the isolated IgM immunoglobulin, including light chain type, association constant, and valence.

Main Results:

• Only one human serum, from a patient with Waldenström's macroglobulinemia, reacted with phosphorylcholine.
• The active protein was identified as a kappa-type IgM immunoglobulin.
• The binding reaction was exothermic, with valences of 10, 2, and 1 for pentamer IgM, 7S IgM, and Fab fragment, respectively.

Conclusions:

• Anti-phosphorylcholine activity is exceedingly rare in human myeloma.
• The characterized human IgM exhibits fundamental characteristics of conventionally induced antibodies, including high specificity and correct stoichiometry.