The amino acid alternatives at the amino terminal four positions were studied in the light chains from 13 normal humans. Residues characteristics of three variable region subgroup (2 kappa and 1 lambda) were present in each of the 13 individuals, implying that the corresponding genes which encode these subgroups are present in the germ line of each individual. Thus the kappa subgroup genes can not be alleles at a single structural locus. At the amino terminus the light chains from Caucasian, Mongoloid and Negroid individuals could not be distinguished from one another. Although there was a marked similarity between the hertogeneous pool of light chains from a single individual and the pool of mycloma light chains, at position 2 in normal individuals valine was seen at 2-5 times the level present in the mycloma pool. This is, to our knowledge, the first clear example of variable region selection in the myceloma process.
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