β2-Microglobulin Production and Secretion by Lymphocytes in Culture

A β 2 -microglobulin with molecular weight of 12,600 daltons was initially isolated from the urine and serum of patients with renal tubular insufficiency (1). Smithies and Poulik (2) determined the partial amino acid sequence of this globulin and found that 24 of the first 46 amino acid residues were homologous with the amino acid sequence of parts of the heavy chain of the G-1 myeloma protein. This suggested that a structural relationship existed between the β 2 -microglobulin and the constant region of human IgG immunoglobulins. In spite of this structural relatedness, specific antisera against all known immunoglobulin chains (including secretory piece and J-chain) did not react with this protein. Subsequently, Peterson et al. (3) established the complete sequence of this protein and found that 28 amino acid residues of the β 2 -microglobulin were homologous with the C H 3 domain of the myeloma protein. An homologous protein was also isolated recently from the dog (4), and its partial amino acid sequence was established and related to β 2 -microglobulin of human origin.