Contribution of secretory IgA, polymeric IgA and IgA/secretory component-containing circulating immune complexes to the serum hyper-IgA in diabetes mellitus

The impact of the Th17:Treg axis on the IgA-Biome across the glycemic spectrum

Secretory IgA (SIgA) is released into mucosal surfaces where its function extends beyond that of host defense to include the shaping of resident microbial communities by mediating exclusion/inclusion of respective microbes and regulating bacterial gene expression. In this capacity, SIgA acts as the fulcrum on which host immunity and the health of the microbiota are balanced. We recently completed an analysis of the gut and salivary IgA-Biomes (16S rDNA sequencing of SIgA-coated/uncoated bacteria) in Mexican-American adults that identified IgA-Biome differences across the glycemic spectrum. As Th17:Treg ratio imbalances are associated with gut microbiome dysbiosis and chronic inflammatory conditions such as type 2 diabetes, the present study extends our prior work by examining the impact of Th17:Treg ratios (pro-inflammatory:anti-inflammatory T-cell ratios) and the SIgA response (Th17:Treg-SIgA axis) in shaping microbial communities. Examining the impact of Th17:Treg ratios (determined by epigenetic qPCR lymphocyte subset quantification) on the IgA-Biome across diabetes phenotypes identified a proportional relationship between Th17:Treg ratios and alpha diversity in the stool IgA-Biome of those with dysglycemia, significant changes in community composition of the stool and salivary microbiomes across glycemic profiles, and genera preferentially abundant by T-cell inflammatory phenotype. This is the first study to associate epigenetically quantified Th17:Treg ratios with both the larger and SIgA-fractionated microbiome, assess these associations in the context of a chronic inflammatory disease, and offers a novel frame through which to evaluate mucosal microbiomes in the context of host responses and inflammation.

Impact of Diabetes on the Gut and Salivary IgA Microbiomes

Mucosal surfaces like those present in the lung, gut, and mouth interface with distinct external environments. These mucosal gateways are not only portals of entry for potential pathogens but also homes to microbial communities that impact host health. Secretory immunoglobulin A (SIgA) is the single most abundant acquired immune component secreted onto mucosal surfaces and, via the process of immune exclusion, shapes the architecture of these microbiomes. Not all microorganisms at mucosal surfaces are targeted by SIgA; therefore, a better understanding of the SIgA-coated fraction may identify the microbial constituents that stimulate host immune responses in the context of health and disease. Chronic diseases like type 2 diabetes are associated with altered microbial communities (dysbiosis) that in turn affect immune-mediated homeostasis. 16S rRNA gene sequencing of SIgA-coated/uncoated bacteria (IgA-Biome) was conducted on stool and saliva samples of normoglycemic participants and individuals with prediabetes or diabetes (n = 8/group). These analyses demonstrated shifts in relative abundance in the IgA-Biome profiles between normoglycemic, prediabetic, or diabetic samples distinct from that of the overall microbiome. Differences in IgA-Biome alpha diversity were apparent for both stool and saliva, while overarching bacterial community differences (beta diversity) were also observed in saliva. These data suggest that IgA-Biome analyses can be used to identify novel microbial signatures associated with diabetes and support the need for further studies exploring these communities. Ultimately, an understanding of the IgA-Biome may promote the development of novel strategies to restructure the microbiome as a means of preventing or treating diseases associated with dysbiosis at mucosal surfaces.

Proteomic analysis to identify candidate biomarkers associated with type 1 diabetes

PURPOSE

Type 1 diabetes mellitus (DM1) is one of the most common chronic diseases observed during childhood. The incidence of DM1 is increasing worldwide, and there is currently no way to prevent or delay the onset or to cure the disease. Most diseases, including diabetes, stem from abnormalities in the functioning of proteins, and some studies have reported the expression of protein variation to be involved in the development of DM1. Thus, the aim of this study was to investigate the differential expression of serum proteins in patients with DM1.

MATERIALS AND METHODS

Serum of patients with DM1 (n=30) and healthy controls (n=30) was collected. A proteomic approach was used with depletion of albumin and immunoglobulin G chromatography on serum samples followed by data-independent, label-free mass spectrometric analysis.

RESULTS

A total of eight serum proteins were identified as being differentially expressed and involved in the immune system, lipid metabolism, and pathways of coagulation. DM1 was associated with the upregulation of six proteins: alpha-2-macroglobulin, apolipoprotein A-II, β2 glycoprotein I, Ig alpha-2 chain C region, alpha-1-microglobulin, and prothrombin. A total of two proteins were downregulated, including pregnancy zone protein and complement C4.

CONCLUSION

To the best of our knowledge, these findings show differential expression of proteins revealing new proteins that may be involved in the development and progression of diabetes.

Prevalence of selective immunoglobulin A deficiency in Greek children and adolescents with type 1 diabetes

BACKGROUND

The association of selective immunoglobulin A (IgA) deficiency with type 1 diabetes (T1D) remains unclear. This study was to evaluate serum IgA concentrations in Greek children and adolescents with T1D.

METHODS

In two hundred individuals with T1D, serum IgA concentrations were quantitatively determined using nephelometry.

RESULTS

Immunoglobulin A deficiency was detected in 6 (3.0%) of 200 patients who were subjected to immunological evaluation. Recurrent infections were not recorded, but human papilloma virus infection was clinically suspected and confirmed by laboratory examination in a 5-year-old girl. In regard to coincidence of selective IgA deficiency with autoimmune diseases, celiac disease was detected in a girl and juvenile idiopathic arthritis in a boy. Serum IgA concentrations differed significantly when patients were grouped according to age at the beginning of the study (P<0.001), age at diagnosis of T1D (P=0.015) and coincidence of celiac disease (CD) (P=0.038). However, when the age of the patients was adjusted, difference in serum IgA concentrations was not statistically significant despite CD was present or not. Moreover, serum IgA concentrations were positively correlated with serum IgG (P<0.001) and IgE (P=0.001) concentrations and negatively correlated with serum antigliadin antibody IgG (P=0.035) concentrations. There was no association or correlation of serum IgA concentrations with glycemic control.

CONCLUSION

The prevalence of selective IgA deficiency in Greek children and adolescents with T1D is high (3.0%). The correlation of serum IgA concentrations with serum IgG, IgE and anti-gliadin antibody IgG concentrations needs further investigation.

Spinal infections in patients with compromised immune systems

Spinal infections are relatively uncommon but have potentially devastating consequences if not diagnosed and treated correctly. Compromised immunologic responsiveness, either transient or permanent, predisposes patients to more frequent and more severe infections. Through a Medline review of the English-language literature from 1990 to 2005, we examined the current understanding of the etiology of common immunocompromising conditions, how these diagnoses impact the relative spine infection rates including diagnosis and therapeutic monitoring, and practice trends regarding surgical intervention.

LEVEL OF EVIDENCE

Level V (expert opinion). Please see Guidelines for Authors for a complete description of the levels of evidence.

IgA-dominant acute poststaphylococcal glomerulonephritis complicating diabetic nephropathy

Two pathological patterns of acute poststaphylococcal glomerulonephritis are well defined and include (1) an acute proliferative and exudative glomerulonephritis closely resembling classical acute poststreptococcal glomerulonephritis in patients with Staphylococcus aureus infection and (2) a membranoproliferative glomerulonephritis in patients with Staphylococcus epidermidis infection secondary to ventriculovascular shunts. In this study, we report a novel immunopathologic phenotype of immunoglobulin (Ig) A-dominant acute poststaphylococcal glomerulonephritis occurring in patients with underlying diabetic nephropathy. Five patients with type 2 diabetes presented with acute renal failure occurring after culture-positive staphylococcal infection. Renal biopsy disclosed an atypical pattern of acute endocapillary proliferative and exudative glomerulonephritis with intense deposits of IgA as the sole or dominant immunoglobulin, mimicking IgA nephropathy. The deposits were predominantly mesangial in distribution with few subepithelial humps. All five cases occurred superimposed on well-established diabetic nephropathy. Outcome was poor with irreversible renal failure in four of five (80%) cases. The possible pathophysiological basis of this atypical form of acute poststaphylococcal glomerulonephritis in diabetic patients is explored. Proper recognition of this entity is needed to avoid an erroneous diagnosis of IgA nephropathy, with corresponding therapeutic and prognostic implications.

Antibodies to oxidized LDL and LDL-containing immune complexes as risk factors for coronary artery disease in diabetes mellitus

Several groups have published results from clinical studies supporting the involvement of anti-modified LDL antibodies as risk factors for the initiation or progression of cardiovascular disease. However, the data published so far are judged inconclusive because of several contradictory observations concerning the correlation between clinical evidence of arteriosclerosis and the levels of antibodies to oxidized LDL (oxLDL Ab). We have previously reported that oxLDL Ab exist both in free form and as antigen-antibody complexes (LDL-IC) in patients with insulin-dependent diabetes mellitus (IDDM). The presence of LDL-IC in IDDM patients has important implications: it may interfere with the assay of oxLDL antibodies and the levels of LDL-IC may correlate better with the development of arteriosclerosis than the levels of free oxLDL antibodies. To clarify these questions baseline samples collected from 49 IDDM patients, who subsequently developed coronary artery disease (CAD) during an 8-year follow-up period, were compared to baseline samples from 49 age-, sex-, and duration-matched control IDDM subjects who remained free of clinical CAD during an identical follow-up period. The levels of free oxLDL antibody were significantly lower in the patients who developed CAD. The same patients had significantly higher concentrations of total cholesterol, apolipoprotein B, and IgA in immune complex-enriched polyethylene glycol (PEG) precipitates. The concentration of IgG was also higher in PEG precipitates from patients who developed CAD, but did not reach statistical significance. This indicates that patients who develop CAD had higher levels of circulating LDL-IC, a fact that could not be deduced from the measurement of free oxLDL antibody concentrations. A linear regression analysis of the correlation between the concentrations of total cholesterol in PEG precipitates, taken as a surrogate measurement of PEG-precipitated oxLDL-IC, and the concentration of free oxLDL antibody in serum showed a statistically significant negative correlation (r = -0.229, P = 0. 024). Our results support the conclusion that oxLDL-IC may be a risk factor for the development of macrovascular disease in IDDM patients. We also have demonstrated that circulating oxLDL-IC interfere with the assay of free oxLDL antibodies.

Anti-modified LDL antibodies and LDL-containing immune complexes in IDDM patients and healthy controls

Antibodies to oxidized LDL (ox-LDL) and LDL-containing immune complexes (LDL-IC) have been reported to be associated with the presence or progression of arteriosclerosis. We screened for anti-modified LDL antibodies and isolated soluble IC by precipitation with 3.5% (w/v) polyethylene glycol (PEG) 6000 in two groups. The patient group was constituted by 16 insulin-dependent diabetes mellitus subjects free of macrovascular complications. The control group was constituted by 16 healthy, age-, gender-, race-, and body mass index-matched nondiabetic subjects. We detected anti-ox-LDL antibodies and anti-malondialdehyde-modified LDL antibodies with similar levels in patients and controls, while the levels of anti-glycated LDL antibodies were very low, but slightly higher in diabetics than in healthy controls. Isolated LDL-IC were adsorbed to red blood cells (RBC) and incubated with human macrophages for 18 hr at 37 degrees C. Under those experimental conditions, RBC-adsorbed IC are taken up by macrophages but the RBC remain intact and are not ingested. Slightly higher levels of cholesteryl ester (CE) accumulation were measured in macrophages incubated with RBC to which we adsorbed IC isolated from diabetics (15.4 +/- 2.5 micrograms/mg of protein, mean +/- SEM) than in macrophages incubated with IC isolated from controls (12.5 +/- 1.6 micrograms/mg of protein, mean +/- SEM), but the difference did not reach statistical significance. PEG-precipitable IC isolated from both normal and diabetic subjects led, in some instances, to the transformation of macrophages into foam cells. Significant correlations were observed between CE accumulation and the content of apo B (P < 0.0001), total cholesterol (P = 0.0004), IgG (P = 0.015), and IgA (P = 0.015) in the isolated IC. The correlation between CE accumulation and the content of apo B in isolated IC was stronger in diabetics than in the control group (r = 0.759 vs r = 0.500). Fractionation of isolated IC in immobilized protein A/G yielded immunoglobulin-rich fractions which contained cholesterol and IgG anti-ox-LDL antibodies. The cholesterol content of these fractions was significantly correlated (P = 0.001) with CE accumulation. In conclusion, both diabetics and normal individuals have circulating IC whose atherogenic potential appears to be related to the presence of LDL and antibodies of the IgG and IgA isotypes.

Significance of high levels of serum IgA and IgA-class circulating immune complexes (IgA-CIC) in patients with non-insulin-dependent diabetes mellitus

Significance of serum IgA and IgA-class circulating immune complexes (IgA-CIC) elevation in patients with non-insulin-dependent diabetes mellitus (NIDDM) was described. Seventeen patients with NIDDM and 17 patients with diffuse mesangial proliferative glomerulonephritis without deposition of IgA (DPGN) as controls were examined. The levels of serum IgA in patients with NIDDM were significantly higher than those in patients with DPGN (p < or = 0.01). The levels of IgA-CIC in patients with NIDDM were also significantly higher than those in patients with DPGN (p < or = 0.01). Production of IgA derived from B cells and the proportion of IgA bearing B cells in patients with NIDDM were not significantly higher than those in patients with DPGN. Furthermore, the levels of IgA in pharyngeal washings from diabetic patients were not significantly higher than those for DPGN patients. Duration of diabetes, the level of HbA1c, and the presence of hypertension, microalbuminuria, or retinopathy showed no significant correlations with the levels of serum IgA or IgA-CIC in patients with NIDDM. It was postulated that the elevations of serum IgA and IgA-CIC were based on subclinical infection of the mucosa and/or deterioration of IgA clearance in patients with NIDDM.