[Genetic linkage of HLA-Bf. Study of 19 informative families]

Since the discovery of the linkage between HLA and Bf by Allen in 1974 several reports have shown a very close linkage between Bf and HLA-B. We have studied 19 families with 81 offsprings for the linkage between HLA (A,B) and Bf. The total "lod scores" in our material for the linkage between HLA-B and Bf is 17,167 at theta = 0.00. No recombination was observed between HLA-B and Bf. One recombination out of 79 informative meiotic divisions was observed between HLA-A and Bf. This result would mean that the Bf locus is about 1.3% recombination fraction far from the HLA-A locus. Our estimation is in good agreement with the results of other authors. However the estimation of recombination fractions is only an arbitrary mean to map genetic loci on chromosomal regions and family studies of cases with intra-HLA cross-overs are of more interest. All available data from the litterature are in favour to a very close linkage between Bf and HLA-B and to a situation of the Bf locus between HLA-B and HLA-D. However some conflicting data on Bf gene mapping have been published. More precise informations may be obtained as soon as a more exact structure of the HLA region, in particular of the HLA-D region, will be known.