THE HUMAN VH3B-GENE SUBFAMILY IS HIGHLY POLYMORPHIC

We have previously shown that human antibody (Ab) directed against the capsular polysaccharide of the important bacterial pathogen, Haemophi lus influenzae type b (Hib) is encoded by a small group of VH3 gene fa mily members. The majority of anti-Hib PS Ab use members of the smalle r VH3b subfamily. To examine directly the available human VH3 repertoi re, we have used PCR to amplify and clone candidate germ-line VH3b H c hain V region genes from two unrelated subjects from whom anti-Hib pol ysaccharide mAb had been previously obtained. A single functional VH3b germ-line gene was obtained from one subject. This gene is identical throughout the coding region to the previously identified gene 9.1. Tw elve distinct VH3b germ-line sequences, 87.6-99.8% homologous to one a nother, were obtained from the second subject. One of these genes, LSG 1.1, is also identical to the 9.1 germ-line gene, and a second, LSG6.1 , is identical to a previously reported cDNA, M85. These germ-line VH3 b genes are 82.7-94.1% homologous to rearranged anti-Hib PS VH3b segme nts obtained from these subjects. Our findings further demonstrate tha t considerable polymorphism of VH segments exists in the human populat ion. Despite the presence of very highly homologous VH elements in the germ line, particular genes are highly conserved within the outbred h uman population.