A pH-dependent macroglobulin gel.

Plasma from a patient with Waldenstrom's macroglobulinemia was observed to gel upon exposure to room air, yet to remain in solution indefinitely at 4 degrees C if sealed. Three studies were carried out which showed this change not to be due primarily to decreases in carbon dioxide tension or temperature, but to variations in the concentration of hydrogen ions within or just above physiologic levels. In purified material (IgM) a marked increase in viscosity occurred between pH 7.5 and 8.0, followed by precipitation between pH 8.0 and 9.7, and by reversible dissolution between pH 9.7 and 10.0. The analytical and clinical consequences of these solubility changes are discussed.