Immunochemical studies in four cases of alpha chain disease.

Studies of a number of properties of the pathological gammaA-proteins in the first four cases of the recently recognized alpha-chain disease demonstrate that, as in gamma-heavy-chain disease, the abnormal protein is devoid of light chains and represents a portion of the alpha-heavy chain related to the Fc-fragment. In two patients, serum electrophoresis showed a broad abnormal band, whereas in the two others the pathological protein was not noticeable on the electrophoretic pattern. The diagnosis of alpha-chain disease can be established without purification of the protein by immuno-electrophoresis and gel diffusion experiments using selected antisera to gammaA and a reference alpha-chain disease protein. All four proteins belonged to the alpha1-subclass, displayed electrophoretic heterogeneity, and showed a strong tendency to polymerize. The polymers occurred in vivo and were held together both by disulfide bonds and by strong noncovalent forces. Two of the three purified proteins had a very high carbohydrate content. The abnormal protein was always found in concentrated urines in variable but generally low amounts. It was not detected in parotid saliva but was present in significant amounts in jejunal fluid of all four patients. The alpha-chain disease protein was shown to be associated with the secretory piece in external secretions of two patients. The clinicopathological features were strikingly similar in the four patients. All patients were affected with a neoplastic and mostly plasmacytic proliferation involving primarily the whole length of the small intestine and the mesenteric nodes and all exhibited a severe malabsorption syndrome. While Israeli authors have emphasized the frequency of this type of abdominal lymphoma in young Arabs and non-Ashkenazi Jews, two of our patients were Kabyles, one a Syrian Arab, and one an Eurasian. Cellular studies showed that the pathological protein was synthesized by the proliferating cells in the lymphoid tissue of the digestive tract and in the mesenteric nodes, and that there was no detectable light-chain synthesis at the intracellular level.