Studies on the Macroglobulins of Human Serum : III. Quantitative Aspects Related to Cold Agglutinins

Eighteen sera containing cold hemagglutinins were examined. IgM levels were determined before and after absorption of this cold antibody. In 5 sera with M-components (immunologic type M kappa) 33 per cent, 93 per cent, 93 per cent, 95 per cent, and 75 per cent of the total IgM was serologically active—that is, lost after the absorption. In 12 sera with no M-component (polyclonal), 0-24 per cent of the IgM molecules had cold activity. One exception was noted in a serum from a patient with cold agglutinin disease containing no monoclonal M-component, but which lost 66 per cent of its IgM after absorption with stromata. No correlation existed between cold agglutinin titer, total IgM-concentration, or per cent active IgM molecules. The results indicate a general qualitative difference between polyclonal and monoclonal cold hemagglutinins.