RESUMO
The plasma immunoglobulins of patients with severe combined immunodeficiency were studied by immunoelectrophoresis and, following isolation by affinity chromatography, by SDS-polyacrylamide gel electrophoresis. Immunoglobulins in plasma from the eight patients studied were immunoelectrophoretically abnormal. Although certain of the immunoglobulins in plasma from five patients could not be identified antigenically, all possessed two mu determinant-bearing proteins with abnormally fast electrophoretic mobilities. Molecular analysis of immunoglobulins of three of these patients revealed two mu heavy chains of abnormally low molecular weight which lacked the ability to polymerize into the pentameric structure of IgM. The failure of concanavalin A to precipitate these molecules suggests that they lack the carbohydrate moiety of normal IgM. Using these techniques, we documented the acquisition of normal IgM synthesis by a patient grafted with maternal leukocytes and the partial immunologic development of a child maintained under gnotobiotic conditions. In the latter patient, between the age of 1 and 4 years, an abnormal mu component disappeared from plasma and normal IgM appeared.
