Abstract
Direct sequencing of mRNA has shown that the early primary response of the BALB/c mouse to the hapten 2-phenyloxazolone is dominated by antibodies with a particular light chain, V kappa-Ox1. Although the V kappa-Ox1 sequence is still commonly expressed later in the response it now includes a number of nucleotide changes. From two independent BALB/c germ-line DNA libraries 13 different genes hybridizing to a V kappa-Ox1 probe were isolated and characterized. Two are identical to mRNA sequences found in the early primary response, one of which is the V kappa-Ox1 sequence. None of the germ-line clones show the characteristic nucleotide changes contained in the late anti-phenyloxazolone light chain mRNAs. These results demonstrate that the V kappa-Ox1 sequence used in the early primary response is entirely encoded by the germ-line and further substantiate the importance of somatic mutations in the maturation of the anti-phenyloxazolone response. The statistical analysis of the data shows that the V kappa-Ox1 related germ-line gene family contains greater than 20 and probably less than 50 genes.