The V kappa gene repertoire in the human germ line.

The question of how many V kappa gene segments exist in the human germ line was addressed. Seventy-five V kappa genes of the kappa locus and twenty-five V kappa genes localized outside of the locus ("orphons") had been cloned previously; 67 of the genes and 19 of the orphons had already been sequenced yielding 36 and 1 potentially functional V kappa genes, respectively, the remaining ones being pseudogenes. We now (a) determined the relative hybridization intensities of the cloned V kappa genes and orphons, (b) identified the bands in blot hybridizations of genomic DNA digests with the cloned genes and orphons, (c) determined the band intensities in the genomic DNA digests from two individuals and one cell line, (d) normalized the results with the help of the C kappa gene segment which is present in the haploid genome in one copy, (e) compared the genomic blot hybridization patterns with patterns of equimolar mixtures of the cloned V kappa genes and orphons, and (f) defined the bands and fractional intensities in bands that could not be assigned to cloned genes or orphons. From the resulting data we conclude that there are 5-7 still uncloned V kappa genes in germ-line DNA in addition to the 75 known V kappa genes and in addition to the 25 orphons 12-15 orphon candidates. It appears that the rheumatoid factor light chains of the Wa and 6B6.6 idiotypes are coded for by one V kappa III gene each. It is concluded that the kappa locus comprises no more than 50 potentially functional genes and no more than 85 V kappa genes altogether.