Investigation of the mode of inheritance of the HLA associated diseases by the method of antigen genotype frequencies among diseased individuals.

Statistical features of the method of antigen genotype frequencies among the diseased, for single and multiple disease associations at a locus, will be presented. A methodology to determine when a true intermediate mode of inheritance can be distinguished from strict recessive or additive inheritance will be developed. The effect of sporadics and ascertainment bias on the observed antigen genotype frequencies will be investigated. Data on ankylosing spondylitis, multiple sclerosis and dermatitis herpetiformis are very close to expectations for an additive (or dominant) mode of inheritance for the HLA-linked disease-predisposing gene, and data on hemochromatosis, insulin dependent diabetes mellitus and celiac disease are close to recessive expectations. If an intermediate model does apply in any of these cases, it must be an intermediate model that is fairly close to a strict recessive or dominant model; as appropriate. DR data for insulin dependent diabetes mellitus (IDDM) strongly indicate that there are two separate "disease" alleles, which exhibit negative complementation, predisposing individuals to IDDM, where the mode of inheritance of the "disease" alleles considered separately is close to recessive. In general, this method cannot rule out the existence of sporadics or a second disease-predisposing gene, when the penetrance values over the two disease-predisposing genes are strictly additive, for diseases showing agreement with additive (or dominant) modes of inheritance.