Monoclonal IgG1 immunoglobulinaemia with strictly pH dependent cryoprecipitability.

A monoclonal IgG1 lambda protein with peculiar cryoprecipitable characteristics was found in the serum of a patient with advanced multiple myeloma. The cryoprecipitate was observed only when the serum was exposed to the air. Further studies defined this phenomenon as being strictly pH-dependent. No antiglobulin activity (rheumatoid factor) was detected in the cryoglobulin. The isoelctric focussing of isolated cryoglobulin showed four distinct fractions around the pH 7.8 zone, which was comparable to the pH at which the cryoprecipitate began to form. Electrostatic bonds probably contribute to the mechanism involved in the formation of cryoprecipitate in this case.