IgM molecules were purified by the use of anti-IgM antibody-coupled Sepharose from the culture supernatant of an Epstein-Barr-virus-transformed lymphoblastoid cell line, MP1, that secretes alloantibodies possessing HLA-DQw2 specificity as defined by the cytotoxicity assay. The obtained IgM preparation was labeled with radioactive iodine-125I and fractionated by gel filtration. It contained pentameric IgM and smaller oligomeric IgMs. When tested by the direct cellular binding assay against a panel of HLA-typed cell lines, they all showed the DR3 and DR7 association pattern characteristic of DQw2. A weak but significant binding was detected for DR1, DR6, and DR9. On isoelectrofocusing, MP1 pentameric IgM gave a restricted banding pattern comparable to monoclonal IgM obtained from a patient with Waldenström's syndrome. Moreover, the pattern was identical to that of IgM purified from the culture supernatant of a defined hybrid clone, 162, that was generated by fusing MP1 cells with heteromyeloma D33 cells. The target class II molecules showed the dimeric structure that conforms to DQw2 molecules.
ASJC Scopus subject areas
- Immunology and Allergy