MHC classes I, II, III antigens study in 70 insulin-dependent diabetics with associated auto-immune diseases.

Seventy IDDM patients (insulin-dependent diabetics), 48 females and 22 males, most of them adults at the onset of diabetes, and suffering from at least one other associated autoimmune manifestation (AAM) were studied for HLA A,B,C, DR markers and Bf, C4 complement components. Comparisons were made with 108 normal controls and a series of 287 IDDM patients with juvenile onset (under 25 years) and no patent other autoimmune disease. The increase in frequency of HLA-B8 among IDDM patients with AAM was confirmed (36% versus 20% in controls) (p less than 0.04). The frequency of DR4 among diabetics with AAM (33%) was not significantly different from the normal frequency (27%), and the allelic combination DR3/4 was found in only 13% of IDDM with AAM. Corresponding frequencies in patients with IDDM alone were 66% for DR4 and 34% for DR3/4 (p less than 10(-6) and 10(-3) respectively). These results confirm the heterogeneity of IDDM and support, by genetic arguments, the concept of overlapping entities. The hypothesis of a common background of autoimmunity associated with B8 DR3 can be postulated, while the organ specific target process should be associated with various DR alleles.

Study of cis and trans interactions between extended HLA-haplotypes in insulin-dependent diabetes.

From the study of HLA, A, B, C, DR, Bf and C4A, C4B alleles in 287 insulin-dependent diabetes mellitus patients and 108 controls, comparisons were made between 424 diabetic and 216 normal extended haplotypes. In the "cis" situation (haplotype), the highest relative risks (RR) for IDDM were borne by multiloci allelic associations, mainly DR/complement alleles, rather than by DR3 or DR4 considered alone. Susceptibility was strongly associated with two extended haplotypes (Aw30, Cw5, B18, C4BQ0, C4A3, BfF1, DR3 and A2, Cw3, B15, C4Bx, C4A3, BfS, DR4) or their smaller segments. Two haplotypes, S31 associated with DR2 or DR5 and F31 associated with DRw6 or DR7 had a protective effect. In the "trans" situation (opposite haplotype) the large excess of DR3/DR4 heterozygotes was not the only distortion observed. An excess of DR1 (57%) and of C4BQ0 (40%) was noted among non DR3, non DR4 haplotypes in diabetics compared to normal individuals (26% and 23%, respectively, P less than 0.01, 0.05). Homozygotes for DR3 or DR4 were not increased, and other homozygotes were decreased compared to controls. The protective antigens HLA DR2, DR5 and DR7 seemed not to be distributed randomly: their putative protective effect was not observed in the case of combination with DR1 or a B18, DR3 haplotype. DR2 was never found homozygous or combined with DR5. These results suggest that susceptibility to IDDM is generated by both cis and trans interactions between genes or gene products of the HLA region.

Study of HLA antigens in a population of Mali (West Africa).

Eighty-two healthy individuals have been typed for HLA-A, B, C, antigens, and 49 of them also for HLA DR alleles. They were a sample representative of 11 of the 14 Malian ethnic groups living in the area of Bamako (Mali). Phenotypic frequencies have been compared to those of other Negroid and Caucasoid reference populations. As expected, in Negroids the increased frequency of HLA A23, A28, A30, and ATh was confirmed in the present series. Additionally, a significantly increased frequency of HLA B5 (B51 and Bw52) was noted--already observed in some but not all Negroid populations. Conversely, a decreased frequency--compared with that usually found in Negroid population--was observed for the alleles Bw42, Bw58, Cw6, and DRw6. Our results underline the originality of the Malian population among Western Africans.