Quantitation of antibodies to IgM, IgD and beta2-microglobulin in antisera to chronic lymphatic leukemia lymphocytes.

Rabbit antisera were prepared to chronic lymphatic leukemia (CLL) lymphocytes and were tested for their reaction with radioiodinated, solubilized, cell surface proteins of normal and CLL lymphocytes. A pooled, hyperimmune antiserum precipitated at least 16 polypeptides from both normal and CLL lymphocytes as shown by sodium-dodecyl sulfate polyacrylamide gel electrophoresis. These polypeptides varied in molecular weight from 11,000 to 180,000. None was prominent or unique to the CLL lymphocytes, although four peptide bands in the CLL cells usually showed more radioactivity than their counterparts in normal cells. Precipitation with antisera of known specificity showed that the cell surface proteins from CLL and normal lymphocytes included HLA antigens and beta2-microglobulin. IgM and IgD were found in preparations of normal cells and in cells of 3 of 5 CLL patients. Of cells from the other 2 patients, one showed only IgD and the other no Ig. An antigen-binding capacity test was employed to quantitate the antibody content of a pooled anti-CLL lymphocyte serum. The antiserum reacted with all Ig classes; however, after absorption with light chains and F(ab')2 fragments, the serum retained activity only for IgM and IgD. The absorbed antiserum bound 45 microgram IgM, 1.5 microgram IgD and 4.5 microgram beta2-microglobulin per milliliter. These data indicate that rabbit anti-CLL lymphocyte sera fail to detect a qualitatively unique tumor-specific polypeptide on the surfaces of CLL cells. However, such antisera contain antibodies to many cell surface proteins including IgM, IgD, HLA antigens and beta2-microglobulin.