Prevalence of HSP47 antigen and autoantibodies to HSP47 in the sera of patients with mixed connective tissue disease

The 47-kDa heat shock protein (HSP47) is an endoplasmic reticulum molecular chaperone that assists in the maturation of collagen molecules and whose expression is known to be upregulated in lesions of fibrotic diseases. We examined the levels of HSP47 protein and autoantibodies to HSP47 in the sera of patients with rheumatic autoimmune diseases, including rheumatoid arthritis, systemic lupus erythematosus, Sj?gren's syndrome, and mixed connective tissue disease (MCTD) by enzyme-linked immunosorbent assay and immunoblot analysis. Patients with idiopathic pulmonary fibrosis (IPF) were assessed as an example of non-autoimmune fibrotic disease. HSP47 antigen and autoantibody levels are significantly elevated in the sera of the rheumatic autoimmune disease patients, but not in the sera of the IPF patients. The sera of the MCTD patients showed particularly high levels of HSP47 antigen relative to healthy controls (1.99+/-0.22 vs 0.41+/-0.07 ng/ml). Autoantibodies to HSP47 were also in high levels in the sera of MCTD patients. These results suggest that simultaneous occurrence of systemic inflammation and upregulation of HSP47 caused leakage of HSP47 from fibrotic lesions into the peripheral blood, and the leaked antigen induced high titer of autoantibodies to HSP47. The high levels of HSP47 antigen and autoantibody may be useful blood markers of MCTD.     

Autoantibody to DNA binding protein B as a novel serologic marker in systemic sclerosis

Systemic sclerosis is a systemic disease that is characterized by tissue fibrosis, small-vessel vasculopathy, and an autoimmune response associated with autoantibodies. We performed serological analysis of cDNA expression library (SEREX) to identify autoantibodies associated with systemic sclerosis. We identified 4 clones that react with sera of patients with SSc but not with those of healthy donors. These clones are phosphoglycerate mutase, centromere autoantigen C, U1 small nuclear ribonucleoprotein, and DNA binding protein B (dbpB). We chose to study autoantibody to DNA binding protein B. Immunoreactivity against recombinant dbpB was detected in 40.5% (15/37) of patients with SSc, 14.6% (6/41) of patents with systemic lupus erythematosus, 6.7% (1/15) of patients with rheumatoid arthritis, 0% (0/12) of patients with Sjogren syndrome, and 5.9% (1/17) of patients with polymyositis/dermatomyositis. The frequency of anti-dbpB was significantly higher in the SSc patients (15/37, 40.5%) compared to the healthy controls (3/41, 7.3%, p=0.0005 by chi(2) test). Eleven patients (11/20, 55%) with the diffuse cutaneous type of SSc had anti-dbpB and 4 patients (4/17, 23.5%) with the limited cutaneous type had anti-dbpB. The presence of anti-dbpB was significantly associated with the diffuse cutaneous type (p=0.00003 by chi(2) test). This is the first report to suggest that autoantibody to dbpB can be used as a serologic marker of systemic sclerosis.     

Identification of autoantibodies associated with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the presence of antinuclear antibodies. We performed serological analysis of cDNA expression library (SEREX) to identify autoantibodies associated with SLE. The screening of three different cDNA expression libraries with pooled sera of patients with SLE yielded 11 independent clones that reacted with pooled sera of patients with SLE. In this screening, autoantibodies to poly(ADP-ribose) polymerase (PARP), U1snRNP, and galectin-3 were prevalent in the sera of patients with SLE (26/68, 25/68, 12/63, respectively). The frequency of autoantibody to PARP was significantly higher in SLE than that of healthy donors (0/76) (38.2% vs 0%, p<0.00001). The autoantibody to PARP was infrequently detected in the serum of patients with RA (1/50). However, autoantibody to PARP was not found in the sera of patients with other rheumatic diseases including Sjogren's syndrome (0/19), systemic sclerosis (0/18), and polymyositis/myositis (0/37). The frequency of autoantibody to human galectin-3 (12/63) was significantly higher in SLE than that of healthy donors (0/56) (19% vs 0%, p=0.0006). Autoantibody to galectin-3 was not found in the sera of patients with rheumatoid arthritis (0/50), Sjogren's syndrome (0/18), and systemic sclerosis (0/19). Interestingly, autoantibody to galectin-3 was also prevalent in the sera of patients with polymyositis/dermatomyositis (16/37, 43.2%). Further functional characterization of these autoantibodies would be necessary to determine their value as diagnostic markers or to define clinical subsets of patients with SLE. Statistical analysis revealed that the presence of autoantibody to PARP was inversely related with pleurisy, and the presence of autoantibody to galectin-3 related with renal disease.     

Autoantibodies as potential biomarkers for nasopharyngeal carcinoma

Autoantibody signatures, as new biomarkers, may improve the early detection of nasopharyngeal carcinoma (NPC). We constructed a T7 phage cDNA library from mixed NPC tissues, and we isolated 31 tumor-associated proteins using biopan enrichment techniques with sera from NPC patients and from healthy population. DNA sequence analysis showed that among 31 phage-displayed proteins, 22 have sequence identity with known or putative tumor-associated proteins. The results of immunochemical reactivity of patients' sera with phage-expressed proteins showed enrichment in the number of immunogenic phage clones in the biopanning process and also confirmed that antibodies were present in the sera of patients but not in the sera of healthy donors. The autoantibody against phage-expressed protein MAGE, HSP70, Fibronectin, and CD44 measured by ELISA had greater predictive value than that against EBNA-1, respectively. The antibody levels against MAGE in sera positively correlated with the clinical stages of NPC, and the antibody levels against other three proteins partly correlated with the clinical stages of NPC. Our studies suggested that the autoantibodies against tumor-associated antigens in the sera of NPC patients could be used as a screening test for NPC. Studies of the corresponding proteins may have significances in tumor biology, novel drug development, and immunotherapy.     

Extrapancreatic Autoantibody Profiles in Type I Diabetes

Type I diabetes (T1D) is an autoimmune disease characterized by destruction of insulin-producing β-cells in the pancreas. Although several islet cell autoantigens are known, the breadth and spectrum of autoantibody targets has not been fully explored. Here the luciferase immunoprecipitation systems (LIPS) antibody profiling technology was used to study islet and other organ-specific autoantibody responses in parallel. Examination of an initial cohort of 93 controls and 50 T1D subjects revealed that 16% of the diabetic subjects showed anti-gastric ATPase autoantibodies which did not correlate with autoantibodies against GAD65, IA2, or IA2-β. A more detailed study of a second cohort with 18 potential autoantibody targets revealed marked heterogeneity in autoantibody responses against islet cell autoantigens including two polymorphic variants of ZnT8. A subset of T1D subjects exhibited autoantibodies against several organ-specific targets including gastric ATPase (11%), thyroid peroxidase (14%), and anti-IgA autoantibodies against tissue transglutaminase (12%). Although a few T1D subjects showed autoantibodies against a lung-associated protein KCNRG (6%) and S100-β (8%), no statistically significant autoantibodies were detected against several cytokines. Analysis of the overall autoantibody profiles using a heatmap revealed two major subgroups of approximately similar numbers, consisting of T1D subjects with and without organ-specific autoantibodies. Within the organ-specific subgroup, there was minimal overlap among anti-gastric ATPase, anti-thyroid peroxidase, and anti-transglutaminase seropositivity, and these autoantibodies did not correlate with islet cell autoantibodies. Examination of a third cohort, comprising prospectively collected longitudinal samples from high-risk individuals, revealed that anti-gastric ATPase autoantibodies were present in several individuals prior to detection of islet autoantibodies and before clinical onset of T1D. Taken together, these results suggest that autoantibody portraits derived from islet and organ-specific targets will likely be useful for enhancing the clinical management of T1D.     

Identification of kinectin as a novel Behçet's disease autoantigen

There has been some evidence that Beh?et's disease (BD) has a significant autoimmune component but the molecular identity of putative autoantigens has not been well characterized. In the initial analysis of the autoantibody profile in 39 Chinese BD patients, autoantibodies to cellular proteins were uncovered in 23% as determined by immunoblotting. We have now identified one of the major autoantibody specificities using expression cloning. Serum from a BD patient was used as a probe to immunoscreen a lambdaZAP expression cDNA library. Candidate autoantigen cDNAs were characterized by direct nucleotide sequencing and their expressed products were examined for reactivity to the entire panel of BD sera using immunoprecipitation. Reactivity was also examined with normal control sera and disease control sera from patients with lupus and Sj?gren's syndrome. Six independent candidate clones were isolated from the cDNA library screen and were identified as overlapping partial human kinectin cDNAs. The finding that kinectin was an autoantigen was verified in 9 out of 39 (23%) BD patient sera by immunoprecipitation of the in vitro translation products. Sera from controls showed no reactivity. The significance of kinectin as a participant in autoimmune pathogenesis in BD and the potential use of autoantibody to kinectin in serodiagnostics are discussed.     

The heterogeneity of islet autoantibodies and the progression of islet failure in type 1 diabetic patients

Type 1 diabetes mellitus is heterogeneous in many facets. The patients suffered from type 1 diabetes present several levels of islet function as well as variable number and type of islet-specific autoantibodies. This study was to investigate prevalence and heterogeneity of the islet autoantibodies and clinical phenotypes of type 1 diabetes mellitus; and also discussed the process of islet failure and its risk factors in Chinese type 1 diabetic patients. A total of 1,291 type 1 diabetic patients were enrolled in this study. Demographic information was collected. Laboratory tests including mixed-meal tolerance test, human leukocyte antigen alleles, hemoglobinA1c, lipids, thyroid function and islet autoantibodies were conducted. The frequency of islet-specific autoantibody in newly diagnosed T1DM patients (duration shorter than half year) was 73% in East China. According to binary logistic regressions, autoantibody positivity, longer duration and lower Body Mass Index were the risk factors of islet failure. As the disease developed, autoantibodies against glutamic acid decarboxylase declined as well as the other two autoantibodies against zinc transporter 8 and islet antigen 2. The decrease of autoantibodies was positively correlated with aggressive beta cell destruction. Autoantibodies can facilitate the identification of classic T1DM from other subtypes and predict the progression of islet failure. As there were obvious heterogeneity in autoantibodies and clinical manifestation in different phenotypes of the disease, we should take more factors into consideration when identifying type 1 diabetes mellitus.     

Influence of sex and age at onset on autoantibodies against insulin, GAD65 and IA2 in recent onset type 1 diabetic patients.

METHODS: Autoantibodies against insulin (IAA), glutamic acid decarboxylase (GADA) and tyrosine phosphatase IA2 (IA2A) were measured in sera from 448 recent onset patients with type 1 diabetes mellitus (DM) subdivided according to sex (194 female and 254 male) and age at onset (134 patients diagnosed before 10 years, 187 between 10 and 20 years, 66 between 20 and 30 years and 61 over 30 years. RESULTS: Autoantibodies were more frequent in female DM patients (93.8 vs. 86.6%, p = 0.013) due to an increased prevalence of both GADA (86.1 vs. 70.1%) and IA2A (59.3 vs. 49.2%), with GADA levels also significantly higher in women (0.24 vs. 0.18 U, p = 0.0003). When age groups were compared, there was a reduction in prevalence in patients over 20 years for both IAA (70% for patients diagnosed under 20 and 36% for older patients) and IA2A (65 and 25%, respectively). These differences also affected IAA levels, with the highest antibody titres in the youngest group (1,214.1 nU/ml in children under 10 compared to 546.9, 345.6 and 341.1 nU/ml in the subsequent groups; p < 10(-4)). GADA prevalence did not differ significantly between age groups but, nevertheless, autoantibody levels were highest among the oldest type 1 DM patients (0.327 U compared to 0.216, 0.197 and 0.176 U in the decreasing age groups; p < 10(-4)). CONCLUSION: There are sex- and age-related differences affecting the presence and/or titres of beta cell autoantibodies. We speculate that these differences could reflect the severity and specificity of the autoimmune attack against the endocrine pancreas and might influence the rate of progression to type 1 DM or the risk of developing other autoimmune diseases.     

A mimic of viral double-stranded RNA triggers fulminant type 1 diabetes-like syndrome in regulatory T cell-deficient autoimmune diabetic mouse

Human fulminant type 1 diabetes (FT1D) is an extremely aggressive disease. The delay of proper diagnosis results in high mortality. However, the pathophysiology of this disease remains unclear. We took advantage of CD28-deficient NOD (CD28(-/-) NOD) mice, which have limited numbers of regulatory T cells and develop aggressive autoimmune diabetes, to create a FT1D model that mimicked the disease in humans. Young CD28(-/-) NOD mice were injected with polyinosinic-polycytidylic acid to activate innate immunity in an effort to induce diabetes onset. In this model, innate immune cell activation precedes the onset of diabetes similar to ～70% of FT1D patients. Eighty-three percent of CD28(-/-) NOD mice developed diabetes within 1-6 d after injection of polyinosinic-polycytidylic acid. Moreover, T cells infiltrated the pancreatic exocrine tissue and destroyed α cells, an observation characteristic of human FT1D. We conclude that an FT1D-like phenotype can be induced in the background of autoimmune diabetes by a mimic of viral dsRNA, and this model is useful for understanding human FT1D.     

Identification of kinectin as a novel Beh?et's disease autoantigen

There has been some evidence that Beh?et's disease (BD) has a significant autoimmune component but the molecular identity of putative autoantigens has not been well characterized. In the initial analysis of the autoantibody profile in 39 Chinese BD patients, autoantibodies to cellular proteins were uncovered in 23% as determined by immunoblotting. We have now identified one of the major autoantibody specificities using expression cloning. Serum from a BD patient was used as a probe to immunoscreen a λZAP expression cDNA library. Candidate autoantigen cDNAs were characterized by direct nucleotide sequencing and their expressed products were examined for reactivity to the entire panel of BD sera using immunoprecipitation. Reactivity was also examined with normal control sera and disease control sera from patients with lupus and Sj?gren's syndrome. Six independent candidate clones were isolated from the cDNA library screen and were identified as overlapping partial human kinectin cDNAs. The finding that kinectin was an autoantigen was verified in 9 out of 39 (23%) BD patient sera by immunoprecipitation of the in vitro translation products. Sera from controls showed no reactivity. The significance of kinectin as a participant in autoimmune pathogenesis in BD and the potential use of autoantibody to kinectin in serodiagnostics are discussed.     

Proteomics-based identification of autoantibodies in the sera of healthy Chinese individuals from Beijing

The identification of panels of tumor antigens that elicit an antibody response may have utility in cancer screening, diagnosis and in establishing prognosis. However, autoantibodies normally exist in sera of healthy individuals and are enormously diversified. To explore the reservoir of autoantibody in healthy population, we performed a proteomics investigation of autoantibody profiles in the sera of 36 healthy Chinese individuals from Beijing, which may provide valuable reference information to the identification of disease-specific autoantibodies. The results showed that autoantibody profiles varied individually, but some autoantibodies were identified at a high frequency in the healthy population. The autoantibodies against alpha-enolase and those against heterogeneous nuclear ribonucleoprotein L were positive in more than 50% of the sera samples. The autoantibodies identified in more than 20% of samples included those against annexin II, F-actin capping protein beta subunit and calreticulin. Some of these autoantibodies have been previously reported to be involved in autoimmune conditions and cancers. Autoantibodies in the healthy population are important as a foundation from which disease-specific autoantibodies can be defined. Thus our report on autoantibodies in healthy individuals may be useful as a reference for defining new autoantibody biomarkers.     

Autoantibodies specific for the cardiac myosin isoform are found in mice susceptible to Coxsackievirus B3-induced myocarditis

Several mouse strains are susceptible to immunopathic myocarditis after infection with Coxsackievirus B3 (CB3). This disease is associated with autoantibodies that are directed against myosin. In this study we characterized sera from CB3-infected mice for their reactivity with three different myosin isoforms (heart, skeletal muscle, and brain myosins) and for autoantibody isotype by using an ELISA. Competitive inhibition assays and absorption studies with various myosins demonstrated the presence of two autoantibody populations in sera of susceptible A.CA and A.SW mice. The first was specific for cardiac myosin and was mainly IgG. The second antibody population cross-reacted with heart, skeletal muscle, and brain myosin and was mainly IgM. B10.PL/SgSf and B10.A/SgSf mice, which do not develop immunopathic myocarditis, produced only the IgM autoantibody population cross-reactive with all three myosin isoforms. Because the heart-specific myosin autoantibodies were found exclusively in the mouse strains that developed immunopathic myocarditis, they can be considered a serologic marker for autoimmune heart disease.     

Proteomics-based identification of HSP60 as a tumor-associated antigen in early stage breast cancer and ductal carcinoma in situ

The detection of autoantibodies in cancer patients has been shown to constitute an excellent tool for early diagnosis. Because breast cancer still lacks early diagnostic markers, we investigated novel tumor-associated antigens and related autoantibodies in sera from patients with early stage breast cancer compared to autoimmune disease, other cancers, and healthy volunteers, using a proteomics-based approach. Among the 26 protein antigens specifically recognized by early stage breast cancer sera, we focused on Heat Shock Protein 60 (HSP60). Using ELISA, we investigated the frequency of autoantibodies directed against this protein in the sera of 240 individuals, comprising patients with either ductal carcinoma in situ (DCIS) ( n = 49) or early stage breast cancer ( n = 58), other cancers ( n = 20), autoimmune disease ( n = 20), and healthy subjects ( n = 93). Autoantibodies directed against HSP60 were present in 16/49 (31%) early stage breast cancer and 18/58 (32.6%) DCIS patients, compared to 4/93 (4.3%) healthy subjects. In particular, autoantibodies were present in 11/23 patients (47.8%) with high-grade DCIS, compared to 5/26 (19.2%) with low-grade DCIS. HSP60 mRNA levels were significantly higher in primary breast cancer compared to healthy breast tissues. Using immunohistochemistry, we found that HSP60 expression gradually increases from normal through DCIS to invasive tissues. Our results indicate that HSP60 autoantibodies may be of interest in terms of clinical utility for the early diagnosis of breast cancer and more particularly in DCIS. Moreover, HSP60 overexpression during the first steps of breast carcinogenesis may be functionally correlated to tumor growth and/or progression.     

Wuchereria bancrofti: cloning and characterization of heat shock protein 70 from the human lymphatic filarial parasite

Heat shock protein 70 (HSP70) was identified as an immunodominant antigen by screening a Wuchereria bancrofti (Wb) microfilarial cDNA library with pooled Wb-infected sera, with 28% of the immunopositive clones coding for Wb-HSP70. The deduced amino acid sequence showed greater than 97 and 85% identity with HSP70 from filarial nematodes and humans, respectively. Recombinant HSP70 (74 kDa) and a recombinant protein from the C-terminal portion (43 kDa) also reacted with pooled Wb-infected sera, suggesting that the C-terminal region of HSP70 contains at least one antibody epitope. Brugia malayi L3 larvae showed increasing levels of HSP70 with increasing temperatures. Further, a polyclonal mouse anti-Wb-HSP70 antibody had reactivity to the HSP70 of cattle filarial parasite Settaria digitata and to human HSP70 derived from a Hep-2 cell line. Immune reactivity to Wb-HSP70 was strong, with uninfected non-endemic normal sera showing significantly greater reactions than sera from filaria-infected individuals. Both immunodominant self-HSP70 and HSP70 from other microbial infections may be primary targets for developing autoantibodies naturally.     

Screening for associated autoimmunity in type 1 diabetes mellitus with respect to diabetes control

As an autoimmune disease, type 1 diabetes mellitus (DM) can be associated with other autoimmune disorders. The aim of this study was to detect subclinically associated autoimmune thyroid disease, coeliac disease, and Addison's disease. The presence of autoantibodies was evaluated with special regard to the control of diabetes and to the clinical status of the patient. Fifty-one type 1 diabetic patients (22 men, 29 women, mean age 37+/-11 years, mean duration of diabetes 16+/-13 years) were included into this study. Specific antibodies to islet antigens--glutamic acid decarboxylase (GAD65), protein thyrosine phosphatase IA-2alpha, and to thyroid autoantigens--thyroid microsomal peroxidase (TPO) and thyroglobulin (TG) and also thyroid stimulating hormone (TSH) were measured by RIA. Autoantigens of the small intestine--tissue transglutaminase autoantibodies (ATTG), IgA and IgG antibodies to gliadin (AGA-IgA, AGA-IgG) were evaluated by ELISA. Endomysial autoantibodies (EMA) and adrenal cortex antibodies (ACA) were detected by indirect immunofluorescence microscopy. Eleven new cases of thyreopathy (22 % of patients) were detected by the assessment of thyroid autoantibodies and TSH. Two new cases of thyreotoxicosis were diagnosed during the study. Coeliac disease was diagnosed in at least two cases. Addison's disease was not diagnosed, although the ACA were positive in two patients. No influence of single or combined autoantibody positivity on the control of diabetes was found if normal organ function was preserved. In both patients with thyreotoxicosis the control of diabetes was worsened and improved after treatment. The screening of autoantibodies in type 1 diabetic patients could reveal subclinical cases of AITD or coeliac disease. Subclinical forms of these disorders have no influence on diabetes control. However, impaired organ function may be associated with the worsened control of diabetes as we demonstrated on two newly diagnosed cases of thyreotoxicosis. We suggest the need for the follow-up of patients with positive autoantibodies because further deterioration of the respective organs can be expected.     

Genome-wide association analysis of autoantibody positivity in type 1 diabetes cases

The genetic basis of autoantibody production is largely unknown outside of associations located in the major histocompatibility complex (MHC) human leukocyte antigen (HLA) region. The aim of this study is the discovery of new genetic associations with autoantibody positivity using genome-wide association scan single nucleotide polymorphism (SNP) data in type 1 diabetes (T1D) patients with autoantibody measurements. We measured two anti-islet autoantibodies, glutamate decarboxylase (GADA, n = 2,506), insulinoma-associated antigen 2 (IA-2A, n = 2,498), antibodies to the autoimmune thyroid (Graves') disease (AITD) autoantigen thyroid peroxidase (TPOA, n = 8,300), and antibodies against gastric parietal cells (PCA, n = 4,328) that are associated with autoimmune gastritis. Two loci passed a stringent genome-wide significance level (p<10(-10)): 1q23/FCRL3 with IA-2A and 9q34/ABO with PCA. Eleven of 52 non-MHC T1D loci showed evidence of association with at least one autoantibody at a false discovery rate of 16%: 16p11/IL27-IA-2A, 2q24/IFIH1-IA-2A and PCA, 2q32/STAT4-TPOA, 10p15/IL2RA-GADA, 6q15/BACH2-TPOA, 21q22/UBASH3A-TPOA, 1p13/PTPN22-TPOA, 2q33/CTLA4-TPOA, 4q27/IL2/TPOA, 15q14/RASGRP1/TPOA, and 12q24/SH2B3-GADA and TPOA. Analysis of the TPOA-associated loci in 2,477 cases with Graves' disease identified two new AITD loci (BACH2 and UBASH3A).     

Localization of the discontinuous immunodominant region recognized by human anti-thyroperoxidase autoantibodies in autoimmune thyroid diseases

The discontinuous immunodominant region (IDR) recognized by autoantibodies directed against the thyroperoxidase (TPO) molecule, a major autoantigen in autoimmune thyroid diseases, has not yet been completely localized. By using peptide phage-displayed technology, we identified three critical motifs, LXPEXD, QSYP, and EX(E/D)PPV, within selected mimotopes which interacted with the human recombinant anti-TPO autoantibody (aAb) T13, derived from an antibody phage-displayed library obtained from thyroid-infiltrating TPO-selected B cells of Graves' disease patients. Mimotope sequence alignment on the TPO molecule, together with the binding analysis of the T13 aAb on TPO mutants expressed by Chinese hamster ovary cells, demonstrated that regions 353-363, 377-386, and 713-720 from the myeloperoxidase-like domain and region 766-775 from the complement control protein-like domain are a part of the IDR recognized by the recombinant aAb T13. Furthermore, we demonstrated that these regions were involved in the binding to TPO of sera containing TPO-specific autoantibodies from patients suffering from Hashimoto's and Graves' autoimmune diseases. Identification of the IDR could lead to improved diagnosis of thyroid autoimmune diseases by engineering "mini-TPO" as a target autoantigen or designing therapeutic peptides able to block undesired autoimmune responses.     

Use of a High-Density Protein Microarray to Identify Autoantibodies in Subjects with Type 2 Diabetes Mellitus and an HLA Background Associated with Reduced Insulin Secretion

New biomarkers for type 2 diabetes mellitus (T2DM) may aid diagnosis, drug development or clinical treatment. Evidence is increasing for the adaptive immune system’s role in T2DM and suggests the presence of unidentified autoantibodies. While high-density protein microarrays have emerged as a useful technology to identify possible novel autoantigens in autoimmune diseases, its application in T2DM has lagged. In Pima Indians, the HLA haplotype (HLA-DRB1*02) is protective against T2DM and, when studied when they have normal glucose tolerance, subjects with this HLA haplotype have higher insulin secretion compared to those without the protective haplotype. Possible autoantibody biomarkers were identified using microarrays containing 9480 proteins in plasma from Pima Indians with T2DM without the protective haplotype (n = 7) compared with those with normal glucose regulation (NGR) with the protective haplotype (n = 11). A subsequent validation phase involving 45 cases and 45 controls, matched by age, sex and specimen storage time, evaluated 77 proteins. Eleven autoantigens had higher antibody signals among T2DM subjects with the lower insulin-secretion HLA background compared with NGR subjects with the higher insulin-secretion HLA background (p<0.05, adjusted for multiple comparisons). PPARG2 and UBE2M had lowest p-values (adjusted p = 0.023) while PPARG2 and RGS17 had highest case-to-control antibody signal ratios (1.7). A multi-protein classifier involving the 11 autoantigens had sensitivity, specificity, and area under the receiver operating characteristics curve of 0.73, 0.80, and 0.83 (95% CI 0.74–0.91, p = 3.4x10^-8), respectively. This study identified 11 novel autoantigens which were associated with T2DM and an HLA background associated with reduced insulin secretion. While further studies are needed to distinguish whether these antibodies are associated with insulin secretion via the HLA background, T2DM more broadly, or a combination of the two, this study may aid the search for autoantibody biomarkers by narrowing the list of protein targets.