[Genetic markers and disease susceptibility (author's transl)].

The HLA system includes several genes and each of them is polymorphic. Several associations between some HLA alleles and the susceptibility to various diseases are already described. Three kinds of associations are reported: [1] a constant association between an HLA allele and a disease whatever the tested population, [2] an association between the HLA allele and a disease varying according to the tested populations, [3] an association probably due to a mutation of metabolic gene closely linked to HLA. These three kinds of associations probably correspond to three different mechanisms.