Calculation of disease susceptibility gene frequency in insulin-dependent diabetes mellitus.

An analysis of HLA-linked genetical factors conferring susceptibility to IDDM is reported. On the basis of population and family studies a recessive mode of inheritance of disease susceptibility provided by an assumption of HLA-B8-linked DS gene was observed. The characteristic component of the immunogenetical background was the high frequency of HLA-B8 (0.208) and the HLA-A1, B8 haplotype (0.134) (linkage disequilibrium D = 0.1031), reminiscent of that found also in other disorders with autoimmune features, such as Graves disease, SLE, etc. Considering the HLA-B8 and IDDM association, the DS gene frequency (pD = 0.25) was estimated and the gametic association between HLA-B8 andu DS gene was calculated. The low value of penetrancy (4.8%) revealed the important role of non-HLA-linked genetical and environmental factors. The HLA-linked genetic factors in question might be responsible for an inclination to several kinds of autoimmune disorders.