Immunobiology and pathogenesis of alpha chain disease

alpha chain disease, the most frequent of the heavy chain diseases, is a proliferative disorder of B lymphoid cells involving primarily the small intestine and mesenteric nodes. The characteristic immunoglobulin, whose detection by immunochemical techniques may present some difficulties, consists of incomplete alpha chains devoid of light chains. The deleted portion of the alpha chain is located in the Fd segment and involves both the variable and first constant domains. In both of two proteins for which structural data are available, normal sequence resumes at the beginning of the hinge region. The absence of L chains is due to a failure of synthesis. alpha chain disease appears to proceed in two stages. The early stage is characterized by a possibly non-malignant diffuse and extensive plasma cell infiltration which may be reversible after administration of antibiotics. The later stage is characterized by overt neoplasia (immunoblastic lymphoma). The socio-geographic distribution of the digestive form of alpha chain disease shows a clear predilection for underpriviliged populations living in areas with a high degree of infestation by intestinal pathogens which play presumably a crucial role in the pathogenesis of the disease.