Characterization of peptides found in human biological fluids in macroglobulinemia IgM

Excessive production of IgM in macroglobulinemia is accompanied frequently by secretion of proteins and peptides which are normally absent from biological fluids. These proteins and peptides are probably secreted by cells producing IgM. Three types of peptides were isolated and their basic properties are described. One peptide showed calcium-binding properties, and the other two peptides were bound to secreted IgM immunoglobulin.