Comparison of an immunohistochemical and immunofluorescence procedure to detect antibody to pancreatic islet cells

Immunohistochemical and Molecular Investigations Show Alteration in the Inflammatory Profile of Multiple System Atrophy Brain

Multiple system atrophy (MSA) is an adult-onset neurodegenerative disease characterized by aggregation of α-synuclein in oligodendrocytes to form glial cytoplasmic inclusions. According to the distribution of neurodegeneration, MSA is subtyped as striatonigral degeneration (SND), olivopontocerebellar atrophy (OPCA), or as combination of these 2 (mixed MSA). In the current study, we aimed to investigate regional microglial populations and gene expression in the 3 different MSA subtypes. Microscopy with microglial marker Iba-1 combined with either proinflammatory marker CD68 or anti-inflammatory marker Arginase-1 was analyzed in control, SND, and OPCA cases (n = 5) using paraffin embedded sections. Western immunoblotting and cytokine array were used to determine protein expression in MSA and control brain regions. Gene expression was investigated using the NanoString nCounter Human Inflammation panel v2 mRNA Expression Assay. Analysis of neuropathological subtypes of MSA demonstrated a significant increase in microglia in the substantia nigra of OPCA cases. There was no difference in the microglial activation state in any region. Cytokine expression in MSA was comparable with controls. Decreased expression of CX3CL1 precursor protein and significantly greater CX3CR1 protein was found in MSA. NanoString analysis revealed the >2-fold greater expression of ARG1, MASP1, NOX4, PTGDR2, and C6 in MSA.

Familial and sporadic insulin-dependent diabetes: evidence for heterogeneous etiologies?

Heterogeneity within insulin-dependent diabetes mellitus (IDDM) has been hypothesized, but few studies have focused on differences which may exist between familial and sporadic IDDM cases. Presenting characteristics for 330 white, newly diagnosed IDDM cases were evaluated. Familial cases were older (10.2 +/- 5.1 years vs 7.9 +/- 4.2 years, P = 0.010) and had, on average, less severe metabolic disturbances at presentation, as demonstrated by lower mean hemoglobin A1 (12.6 +/- 2.4% vs 14.4 +/- 2.6%, P = 0.001) and mean insulin dose at discharge (0.62 +/- 0.35 U/kg/day vs 0.85 +/- 0.29 U/kg/day, P less than 0.001), and higher mean plasma bicarbonate concentrations (19.3 +/- 3.9 mmol/l vs 15.8 +/- 5.9 mmol/l, P = 0.023) and mean plasma C-peptide levels (0.35 +/- 0.36 pmol/ml vs 0.14 +/- 0.15 pmol/ml, P less than 0.001). Further analyses on a subset of IDDM cases (n = 100) indicated that initial differences in metabolic indices observed at diagnosis were no longer apparent at one-year post-diagnosis. These results suggest that the etiology of familial and sporadic IDDM is similar and that the less severe presentation observed at diagnosis in the familial cases may be due to earlier identification of the disease, reflecting increased parental knowledge of diabetic symptoms and/or frequent testing for diabetes.

Assessment of precision, concordance, specificity, and sensitivity of islet cell antibody measurement in 41 assays

Forty-one assays were analysed at the 3rd International Workshop on the standardisation of islet cell antibodies. Analysis of precision demonstrated assays consistently detecting blind duplicates within one doubling dilution and capable of discriminating one doubling dilution differences in islet cell antibody concentration. Some assays, however, reported duplicates discrepantly by more than seven doubling dilutions, and consequently could not distinguish even large quantities of islet cell antibodies. Precision was best in assays from laboratories which had participated in all three Standardisation Workshops and was not dependent upon methodology. The use of the Juvenile, Diabetes Foundation reference islet cell antibody standard and standard curves reduced the scatter of results, and was best amongst assays with better precision. Twenty-seven assays reported all ten blood donor sera as negative. However, 14 assays did not, and specificity (negativity in health) was less than 50% in three assays. Low specificity was strongly associated with poor precision. The detection limit of assays ranged from less than 5 to 50 JDF units and was partially dependent upon methodology. Assays incorporating extended incubation had the lowest detection limits without a decrease in the specificity of the ten blood donor sera. Precise quantification is fundamental for the standardisation and comparability of islet cell antibodies. Precise quantitative assays have been identified and reference standards and common units established.

Analyses on possible heterogeneity of IDDM based on presence of islet cell cytoplasmic antibody at diagnosis

In a large, representative sample of newly-diagnosed IDDM patients, using a highly sensitive assay to detect islet cell cytoplasmic antibodies (ICA), no marked differences were found between ICA+ and ICA- patients on various clinical, genetic, immunologic, and epidemiologic characteristics. In particular, there was no evidence for associations between ICA status at diagnosis and either sex, race, family history of IDDM, HLA-DR phenotype, antibody titers to Coxsackie B viruses, immunoglobulin levels, C-peptide and glycosylated hemoglobin concentrations, or insulin requirements. The most significant relationship was between the presence of ICA and a young age at diagnosis; however, the large overlap between the distributions of the ages at onset for ICA+ and ICA- groups on this variable suggests that this association is of limited importance. These data suggest that the presence or absence of ICA at diagnosis may not be useful in defining possible subtypes of IDDM.

Presence of complement-dependent cytotoxic activity against clonally-derived rat islet tumour cells in sera from type 1 (insulin-dependent) diabetic patients and control subjects

Heat-inactivated sera from newly diagnosed Type 1 (insulin-dependent) diabetic patients and control subjects were tested for the presence of antibodies to islet cell surface antigens by means of a sensitive immunofluorescent, microcytotoxicity assay using two clones of a rat islet cell tumour as antigens. Complement-dependent cytotoxicity was found in 74% of diabetic patient sera and 87% of control sera, and there were no significant differences in titres between diabetic patients and control subjects. A minority of the sera from both patients and controls were cytotoxic for only one of the two clones, suggesting the presence of multiple antigen-antibody systems. Preadsorptions of the sera with rat liver powder, sheep erythrocytes, and/or protein A-conjugated agarose beads were inconsistently effective in decreasing levels of lytic activity in control sera. It is concluded that more information is required concerning the antigens of rat islet cells and islet cell cytotoxic factors present in normal sera before such cells and assays can be reliably used for the detection of islet cell surface antibodies.

Height at diagnosis of insulin dependent diabetes in patients and their non-diabetic family members

Height at the onset of insulin dependent diabetes mellitus was evaluated in 200 newly diagnosed children, 187 non-diabetic siblings, and 169 parents. Diabetic children 5-9 years of age at diagnosis were consistently taller than the national average. Non-diabetic siblings of the same age were also tall. Diabetic children aged 14 or over at diagnosis were short, while their siblings and parents were of normal height. Diabetic children positive for islet cell antibodies were taller than those without islet cell antibodies. No association between height and HLA antigens was found. Non-diabetic siblings at high risk for the disease were closer in height to the diabetic children than were the lower risk, non-diabetic siblings. Siblings, particularly those under 10, were also significantly more obese than the general population. Deviations in growth in patients with insulin dependent diabetes mellitus appear to be related to age at diagnosis and a factor(s) not related to parental height.

Glucose tolerance in siblings of type 1 diabetic patients: relationship to HLA status

In this report, we present an analysis of glucose and insulin responses during oral glucose tolerance tests in 369 siblings of Type 1 diabetic patients. All have been HLA typed at the A, B and C loci. Though most had normal glucose tolerance by National Diabetes Data Group criteria (92% of the males and 95% of the females), siblings who shared both HLA haplotypes with the diabetic patient in the family had higher mean 3-hour glucose areas than those who shared one or neither HLA haplotype (p less than 0.01). This difference was more marked in males and older siblings. Insulin concentrations did not differ significantly between the two groups except that, for those aged less than 16 years, the group sharing both haplotypes had lower fasting insulin concentrations (p = 0.05); for 16-29 year olds, the corresponding group had marginally higher 3-hour insulin areas than the remainder of siblings (p = 0.17). Little association with specific haplotypes (A1B8 or A2B15) was seen. Multivariate analyses, adjusting for age and obesity, eliminated the 3-h glucose difference in females by HLA sharing status (p = 0.37) although in males it remained significant (p less than 0.001). Failure to account for age, sex and obesity may explain some of the conflicts in the reported literature. The glucose tolerance differences seen by HLA haplotype sharing status did not correlate with the presence of anti-islet cell antibodies. These results are consistent with the hypothesis that the HLA identical siblings, particularly males, have different (i.e. worse) glucose tolerance than their haploidentical and non-HLA identical siblings.