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Coeliac disease (CD) is a malabsorption syndrome mediated by gluten toxicity. In almost all populations studied CD is strongly associated with HLA.DR3 and to a lesser extent with DR7, the frequency of DR2 is often low. There is a highly significant excess of DR3/DR7 heterozygotes. Although the association of CD with HLA has been known for 15 years the mode of transmission is poorly understood. In multiple case families the segregation of haplotypes is in favour of a recessive mode of inheritance with low penetrance. The rare cases of CD negative for DR3 and DR7 are positive for DR4 and negative for DQw2, ruling out the intervention of DQw2 by linkage disequilibrium. A recent study tends to show an hyporesponsiveness of T lymphocytes from patients to an antigenic extract of gluten.

A linkage disequilibrium was searched for between HLA-DR antigens and rheumatoid factor level both measured using latex agglutination and a solid phase immuno-enzymic assay (FR-PAP) among 251 sera from patients suffering from classical rheumatoid arthritis for at least 5 years, recorded in the Cooperative Swiss Study on Rheumatoid Arthritis. An association between the presence of HLA-DR7 and low levels of rheumatoid factor was found. This association was stronger when the DR4, 7 heterozygous subjects were excluded. The comparison of the DR7, not equal to 4 and DR not equal to 4, not equal to 7 subjects demonstrated that the DR7 effect was independent of DR4. Although the association between DR4 and high levels of rheumatoid factor was not statistically significant in this study, these data suggested an opposite influence of DR4 and DR7 on rheumatoid factor level among rheumatoid arthritis suffering patients. The influence of DR4 appeared to be dominant among heterozygous DR4, 7 patients.

Genetic susceptibility (HLA types), clinical and pathological findings, amount of acetylcholine receptor antibodies and T lymphocyte subpopulations were studied in 63 patients with Myasthenia Gravis (MG). The frequency of HLA-DR5 was increased among patients (0.50 versus 0.23 in controls, pc less than 0.01, relative risk 3.3) and that of HLA-DR3 previously described as associated with MG was slightly increased (0.31 versus 0.20 in controls). The relative frequencies of two T cell subpopulations (T4 helper and T8 suppressor/cytotoxic lymphocytes) were normal in HLA-DR5 positive patients while the ratio T4/T8 was increased in other MG patients, who were HLA-DR3 (p less than 0.005). The high rate was due to an increase in the absolute number of T4 lymphocytes (p less than 0.001). HLA-DR3 patients were mostly women with early onset of a severe form of the disease, marked by the presence of thymic follicular lymphoid hyperplasia. A third genetic susceptibility to this disease was recently described in patients treated with D-penicillamine, the antigenic frequency of HLA-Bw35, DR1 is significantly increased. These 3 types of association between HLA and myasthenia gravis can be related to three different physiopathological mechanisms: the first two are probably linked to individual immunity (inductor/suppressor disequilibrium), in the third association, the mechanism is immunopharmacological.

High prevalence of HLA DR7 was well documented in idiopathic nephrotic syndrome (INS) of childhood. Our data in 43 INS, child and adult patients, did not show any significant difference from control group, specially for HLA DR7. Moreover a significant difference occurred when the data was compared in child and adult INS patients. HLA DR7 was more frequent when the nephrotic syndrome appeared before 15 years old. There was no correlation between the presence of HLA DR7 and those of allergy history or increased serum IgE level, on the opposite with previous data. The presence of DR7 would favor its onset at an earlier age. Alternatively, the difference in DR7 prevalence could be an additional argument for considering that the corticosensitivity and negative histological criteria might collect, under the same name, different glomerulopathies.