Somatic recombination of duplicated genes: an hypothesis on the origin of antibody diversity.

The specificity of antibodies for different antigens appears to result from differences in the amino acid sequences of both the heavy and the light polypeptide chains of which antibody molecules are composed. -4 Although specific antibodies are too heterogeneous for complete amino acid sequence analysis, homogeneous iminunoglobulins may be obtained for this purpose from various plasma cell tumors. Bence-Jones proteins have been shown to be light polypeptide chains5' 6 and data have accumulated on the amino acid sequences of various samples of both humanl-9 and murine origin.'0'" These amino acid sequence analyses show that light polypeptide chains of type K (K chains) are composed of 212-214 amino acid residues.'2 From residue 1