Mary E. Witt

The HLA System in Congenital Rubella Patients With and Without Diabetes

The HLA antigens of 173 patients with the congenital rubella syndrome (CR) are reported. Twenty-one of these patients are also clinically diabetic, and among them the frequencies of the HLA antigens DR2 and DR3 are significantly lower and higher, respectively, than in CR patients without diabetes or in controls. These data suggest that the genes that control susceptibility to type I or insulin-dependent diabetes mel-litus are necessary for the development of glucose intolerance in CR patients.

Anti-Insulin Antibodies in Children With Type I Diabetes Mellitus: Genetic Regulation of Production and Presence at Diagnosis Before Insulin Replacement

We evaluated the production of antibodies against insulin in a genetically well-defined population. In the first study, 124 young patients with type I diabetes for longer than 6 mo were included. Anti-insulin antibodies were detected by polyethyleneglycol (PEG) precipitation after incubation of acidified, charcoal-stripped sera with 125I-labeled pork insulin andwere expressed as microunits insulin bound per milliliter whole serum. For comparison, the patients were divided into six groups based on HLA DR antigens: 3/3, 3 /−, 4/4, 4 /− , 3/4, and − / − (– is non-DR3 or -DR4). The mean age of the patients was 14.7 ± 0.5 yr; the duration of diabetes was 5.8 ± 0.4 yr; and the glucose control, as measured byhemoglobin A1c was average (7.6 ± 0.2%). There were no significant differences in any of these parameters among the patients in any of the HLA DR groups. Patients expressing DR3/3 had significantly lower insulin binding than the rest of the groups (2.5 ± 0.4 vs. 13.6 ± 1.4 μU/ml, P < 0.0001). Patients with DR3/− did not differ in insulin-binding capacity from the other groups. The type of insulin used for replacement was not correlated with the serum insulin-binding capacity. In a second study, sera from 48 children, newlydiagnosed with type I diabetes, were examined for the presence of insulin binding before treatment with exogenous insulin and compared with sera from 80 children without diabetes or a family history of diabetes and from 103 unaffected HLA-identical or haploidentical siblings of a child withtype I diabetes. The sera from the newly diagnosed diabetics bound significantly more insulin in the assay (1.02 ± 0.06 μUsol;ml than the sera from either of the two control groups (0.52 ± 0.01 and 0.51 ± 0.02%, respectively, P = 0.0012). Sera from the newly diagnosed girls bound significantly more insulin than did those from the boys (1.13 ± 0.09 vs. 0.89 ± 0.07%, P < 0.02), and there was a highly significant (P = 0.0017) negative correlation between the age at onset of diabetes and the insulin bound by serum before insulin treatment. Finally, sera from six siblings of type I diabetics who became diabetic themselves were obtained when these children were metabolically normal and again just before insulin treatment was begun. Four of these children had a significant increase in their serum insulin binding from normal values to clearly elevated levels over intervals before metabolic decompensation. These data support the following conclusions. The reduced insulin binding previously observed in type I diabetics expressing HLA DR3 can be entirely attributed to the very low binding in individuals homozygous for this antigen. Thus, human antibody response to exogenous insulin is probably regulated by a dominant gene in negative linkage disequilibrium with HLA DR3. Most younger patients have detectable insulin binding at diagnosis of type I diabetes. The level of binding is reduced in older patients, suggesting either that younger children have a better response to insulin released from injured β-cells in a form that is antigenic or that younger children have animmaturity in the clearance of antigen-antibody complexes. Our preliminary data suggest that the elevation in insulin binding is a late event in the pathogenesis of type I diabetes, occurring soon before the symptoms are present.

HLA Antigens, Cytoplasmic Islet Cell Antibodies, and Carbohydrate Tolerance in Families of Children with Insulin-dependent Diabetes Mellitus

Cytoplasmic pancreatic islet cell antibodies were found in 21﹪ of 244 unaffected first degree relatives of type I diabetic patients. Twenty-five percent of HLA-identical, 35﹪ of HLA-haploidentical, 16﹪ of HLA-nonidentical siblings, and 14﹪ of parents were ICA-positive. In the HLA-identical sibs, irrespective of ICA, and in the 18 ICA-positive parents but not the other groups, increased plasma glucose levels were observed after the administration of glucose. In most children, these were associated with reduced insulin levels, while in the adults elevated insulin responses were noted. In 48﹪ of the ICA-positive children and 84﹪ of the ICA-positive parents, other evidence of “autoimmunity” was obtained either by history or by testing for specific autoantibodies. Two of the originally unaffected HLA-identical and ICA-positive siblings developed diabetes during the course of the study. These findings, plus previously reported data in families with two diabetic sibs demonstrating that the empiric risk for developing IDDM is of the order of 30﹪ for HLA-identical sibs but < 5﹪ for those that are HLA-haploidentical, suggest that HLA-identity may be a useful predictor of potential type I diabetes. The presence of ICA may, at times, portend the need for future antidiabetic therapy but prospective studies must be continued to fully elucidate this relationship.

Thyroid autoantibodies in HLA-genotyped type 1 diabetic families: sex-limited DR5 association with thyroid microsomal antibody.

Thyroid autoantibodies are common in Type I diabetics and their first degree relatives and may be part of the autoimmune diathesis present within such families. We have measured the prevalence of microsomal (M‐Ab) and thyroglobulin (Tg‐Ab) autoantibodies in 84 HLA‐typed families having a Type 1 diabetic child, using enzyme‐linked immunosorbent assay techniques. Thyroid autoantibodies were detectable in 201/407 (49%) individuals in these families. Both autoantibodies were significantly more frequent in the subsets of parents, diabetic children and their non‐diabetic siblings than in groups of control adults and children. The prevalence of these autoantibodies in the diabetic families was increased in both sexes with a female:male ratio of 1.4:1. Antigen DR5 was significantly associated with M‐Ab production but only for male subjects (P= 0.005 after correction for the number of DR antigens tested). No significant associations were encountered for Tg‐Ab. Within‐family analyses indicated that thyroid autoantibodies occurred with increased prevalence in HLA‐identical or haplo‐identical siblings of autoantibody‐positive index cases in comparison to control children. We conclude (1) the DR association with thyroid autoantibody production in this diabetes‐selected population was thyroiditis‐related and not diabetes‐related, and (2) the DR5 association was restricted to males and the production of M‐Ab. These data are consistent with the hypothesis that multiple genetic and non‐genetic factors played a role in the high prevalence of thyroid autoantibodies in this population.

ANALYSIS OF BIO(B) AND IMMUNO(I)-LH DURING PUBERTY: A LONGITUDINAL STUDY IN NORMAL BOYS

As part of a serial assessment of normal children throughout puberty, gonadotropins (B- and I-LH) were measured by sensitive RICT assay and RIA in 20 boys and related individually to chronologic (CA) and skeletal age (BA), stage of pubertal development and sex steroid levels. The boys were studied at 6-month intervals for 5 to 6 years. In overall data, B-LH and I-LH were highly correlated (r=.73,p<.001). In 52 samples during prepuberty, I-LH was detectable in 79%, but B-LH in only 27%(X2=28.13, p<.001). Time of initial detection of B-LH differed from I-LH in CA (11.5 vs 10.7,p<.02), BA (10.8 vs 9.9,p<.01) and in levels of testosterone (T) (17.8 vs 12.4,p<.04). A significant linear relationship existed between B-LH or I-LH and T in 70% of the boys. Fitting a quadratic model to these data significantly improved LH-T correlations, suggesting a plateau of LH after the early T rise. There was no significant relationship between B-LH or I-LH and E2 in 13 individual boys. In conclusion: (1) I-LH is detectable by sensitive RIA more commonly than B-LH by sensitive RICT in prepubertal boys; (2) I-LH was measurable at a younger CA and BA, and at a lower T than B-LH; this discordance affirms that which has recently been described in analysis of pulsatile LH secretion, but does not clarify the role of the early pubertal increment of T upon a changing B/I ratio; (3) The relationship between I-LH and/or B-LH and T seems best described by a quadratic equation.

904 HEMOGLOBIN A1C AND |[ldquo]|TIGHT|[rdquo]| BLOOD GLUCOSE CONTROL IN NEWLY DIAGNOSED JUVENILE DIABETICS

The recent demonstration that glycosylated hemoglobin measurements correlate with integrated blood glucose levels over the preceding 1 to 2 months and the mounting experimental evidence that maintenance of normal blood glucose levels may reduce diabetic complications, suggests that early vigorous treatment of newly diagnosed juvenile diabetics, monitored by Hb A1C measurements, may be important in the long-range managements of these children. Fifteen youngsters, ages 3 to 18, were studied at the time of diagnosis of insulin-dependent diabetes and sequentially at 1 to 2 months intervals. Initial concentrations of Hb A1C were 8.6±1.2% of total hemoglobin (normal, non-diabetic children 2.2-4.8%), indicating the presence of hyperglycemia for a significant period of time prior to diagnosis. Within 4 to 6 weeks after diagnosis and placement of the children on a therapeutic regimen designed to promote normoglycemia, Hb A1C values declined to 5.4±0.9% and were maintained at these levels in 12 of the 15 patients for periods ranging up to one year. No significant hypoglycemic reactions occurred in any of the children on the “tight control” protocol which included high protein meals plus 3 snacks per day, daily afternoon exercise and a combination of intermediate and short acting insulin given once or twice per day. The results indicate that it is possible to maintain insulin dependent diabetic children in a relatively euglycemic state that can be monitored sequentially by Hb A1C determinations.