Diabetes 56:2400-2404, 2007 DOI: 10.2337/db07-0416 © 2007 by the American Diabetes Association
Screening for Insulitis in Adult Autoantibody-Positive Organ DonorsFrom the Diabetes Research Center, Brussels Free University and Juvenile Diabetes Research Foundation Center for Beta Cell Therapy in Diabetes, Brussels, Belgium Address correspondence and reprint requests to Peter In't Veld, PhD, Department of Pathology, Brussels Free University, Laarbeeklaan 103, B-1090 Brussels, Belgium. E-mail: intveld{at}vub.ac.be
Abbreviations:
aAb, autoantibody; GADA, glutamate decarboxylase autoantibody; IAA, insulin autoantibody; IA-2A, insulinoma-associated protein 2 autoantibody; ICA, islet cell antibody; LCA, leukocyte common antigen
Antibodies against islet cell antigens are used as predictive markers of type 1 diabetes, but it is unknown whether they reflect an ongoing autoimmune process in islet tissue. We investigated whether organs from adult donors that are positive for autoantibodies (aAbs) against islet cell antigens exhibit insulitis and/or a reduced ß-cell mass. Serum from 1,507 organ donors (age 25–60 years) was analyzed for islet cell antibodies (ICAs), glutamate decarboxylase aAbs (GADAs), insulinoma-associated protein 2 aAbs (IA-2As), and insulin aAbs. Tissue from the 62 aAb+ donors (4.1%) and from matched controls was examined for the presence of insulitis and for the relative area of insulin+ cells. Insulitis was detected in two cases; it was found in 3 and 9% of the islets and consisted of CD3+/CD8+ T-cells and CD68+ macrophages; in one case, it was associated with insulin+ cells that expressed the proliferation marker Ki67. Both subjects belonged to the subgroup of three donors with positivity for ICA, GADA, and IA-2-Ab and for the susceptible HLA-DQ genotype. Comparison of relative ß-cell area in aAb+ and aAb– donors did not show a significant difference. Insulitis was found in two of the three cases that presented at least three aAbs but in none of the other 59 antibody+ subjects or 62 matched controls. It was only detected in <10% of the islets, some of which presented signs of ß-cell proliferation. No decrease in ß-cell mass was detected in cases with insulitis or in the group of antibody+ subjects. Type 1 diabetes results from a specific and major loss of insulin-producing ß-cells presumably through a T-cell–mediated process (1–5). At clinical onset, patients present circulating autoantibodies (aAbs) against islet cell antigens, which can appear many years before hyperglycemia is established and which are therefore used for prediction of the disease. In first-degree relatives of type 1 diabetic patients, the risk for developing the disease is higher when multiple positivity is present for aAbs against the islet cell cytoplasm (islet cell antibodies [ICA]), insulin (insulin aAbs [IAA]), the 65,000 Mr isoform of glutamate decarboxylase (glutamate decarboxylase aAbs [GADA]), or the insulinoma-associated protein 2 tyrosine phosphatase (insulinoma-associated protein 2 aAbs [IA-2A]) (6–12). Antibody positivity is therefore used for patient recruitment in prevention trials, but it is still unknown whether it corresponds to an insulitis process in the pancreas and, if so, for which combination. There are only few studies available on the histopathology of the pancreas in antibody+ nondiabetic individuals (13,14). In the four reported cases, no leukocytic islet infiltrate or signs of ß-cell damage were noticed; three of them were GADA+ patients with polyendocrinopathy, and one was an IA-2A+ organ donor. In the present study we investigated the pancreas in 62 aAb+ organ donors. This larger series allowed us to identify two cases with insulitis, one of whom presenting signs of ß-cell proliferation, and to correlate these histopathological findings to the small subgroup of patients with three or four aAbs and a high-risk genotype.
Collection of pancreatic tissue. Pancreas biopsies were obtained from the Beta Cell Bank, which operates for a clinical trial on islet cell transplantation in Belgium (15,16). They were taken as part of a quality control procedure that was approved by the ethics committees of the Belgian Diabetes Registry and participating hospitals. Tissue ( 0.5 cm3) was excised from the body region of cold-preserved (UW flushed) donor organs that were provided by Eurotransplant Foundation (Leiden, The Netherlands). It was fixed in 4% (vol/vol) phosphate-buffered formaldehyde, pH 7.4, or Bouin's fixative; embedded in paraffin; and then histologically analyzed. Between 1989 and 2004, a total of 1,507 biopsies were collected from patients aged 25–60 years for whom serum or plasma was also available for islet cell antibody assays. For none of these donors was diabetes mentioned in the donor information sheets.
Analysis of donor blood for aAb and genetic risk markers for type 1 diabetes.
Screening for insulitis.
Characterization of leukocytic infiltrates.
Quantification of relative ß-cell area and ß-cell proliferation.
Screening of organ donors for risk markers of type 1 diabetes. Testing for the four IAAs resulted in 62 positive cases (aAb+) of 1,507 donors in the age-group of 25–60 years (4.1%). Most cases were positive for a single aAb (n = 55), with only four double, two triple, and one quadruple positive case(s) (Table 1). The three donors with 3 aAbs displayed a susceptible HLA-DQ genotype, whereas the four cases with only two aAbs exhibited a neutral or protective HLA-DQ genotype (Table 1). We observed lower aAb titers in the single aAb cases than in the multiple aAb cases (results not shown), probably as a result of their high fraction of "statistical positives " (1% cutoff). A control group of 62 aAb– donors was selected from the total donor group by matching for age, sex, and BMI.
Screening of organ donors for insulitis and histopathology of positive cases. Of the 62 antibody+ and 62 antibody– donors, only two cases presented islets with insulitis as defined under RESEARCH DESIGN AND METHODS; they belonged to the small subgroup (n = 3) with positivity for 3 aAbs (Table 1). Case subject 1 (M-59y) died 10 h after hospitalization for a subdural hematoma (plasma glycemia 6.4 mmol/l at admission), and case subject 2 (F-46y) died 43 h after hospitalization for subarachnoidal hemorrhage (plasma glycemia 8.2 mmol/l at admission). In case subject 1, 5 of the 58 examined islets (9%) showed peri- or central insulitis. Four of these islets contained both insulin+ and glucagon+ cells, whereas one was insulin negative and mainly composed of glucagon+ cells. No other insulin–/glucagon+ islets were detected in this donor. In case subject 2, 27 of 917 islets (3%) presented insulitis (Fig. 1A and B), all islets containing insulin+ and glucagon+ cells. Another 3% of the islets were insulin negative and mainly composed of glucagon+ cells; these islets did not present signs of insulitis (Fig. 1C).
In both cases, the infiltrating cells predominantly corresponded to CD3+CD8+ T-cells (Fig. 1G–I) and CD68+ macrophages (Fig. 1F), with a few CD20+ B-cells and CD3+CD4+ T-cells detected (Table 2).
ß-Cell surface area and proliferation in donors with high-risk markers for type 1 diabetes. When the average ß-cell surface area in antibody+ donors with 2 aAbs was compared with that in donors with a single aAb or that in antibody– controls, no significant difference was noted (Table 3). Individual values in case subjects with multiple aAbs fell within the range of the control group.
The average percentage of insulin+ cells that were also positive for the proliferation marker Ki67 was very low (<1 ) in the three groups. The range in aAb negatives was 0–7 . Only one aAb+ case presented a value outside this range (49 ). This case was characterized by insulitis and positivity for the four aAbs (case subject 1); the Ki67+ cells were only noticed in islets with a leukocytic infiltrate (Fig. 1D and E; Table 3).
In the present study, we have screened for insulitis in pancreatic tissue from 62 adult organ donors carrying aAb risk markers for type 1 diabetes. Insulitis was detected in two of three cases with at least three aAbs, be it in <10% of the islets. It was not found in any of the 59 case subjects with only one or two aAbs or in any of the 62 antibody– control subjects. Both case subjects also presented a susceptible HLA-DQ genotype. There were no signs of a reduced ß-cell mass in the two insulitis case subjects nor in the group of aAb+ donors. These data demonstrate that insulitis is a rare phenomenon in aAb+ nondiabetic adults. Insulitis is also a rare finding at clinical onset of type 1 diabetes after 30 years of age, which contrasts with its detection in all onset patients younger than 7 years of age (4). Although type 1 diabetes in adults is, by definition, characterized by the presence of aAbs, a combination of three or more of such aAbs in association with a high-risk genotype is infrequent, especially in latent autoimmune diabetes in adults (20). The absence of insulitis in most adult aAb+ donors does therefore not exclude progression to the disease. The present observations should, however, be interpreted with caution in terms of their possible significance for the development of type 1 diabetes. The seven donors with more than one antibody risk marker were older than 38 years, an age that is not typical for the development of classical type 1 diabetes. Moreover, four of them presented with a protective HLA-DQ genotype that may have modulated an autoimmune response. It is nevertheless conceivable that the presence of insulitis in two subjects with four risk markers illustrates a stage in the disease process that might eventually lead toward a sufficient ß-cell loss such that diabetes develops. However, no decrease in ß-cell mass became apparent after measuring relative ß-cell surface area. There were also no substantial numbers of pseudo-atrophic islets (1) as a remnant of prior destructions and a sign of self-limiting insulitis at an earlier age. It is conceivable that both subjects exhibit a low-intensity autoimmune process affecting only a small percentage of the islets. The occurrence of Ki67+ ß-cells in some of the infiltrated islets raises the possibility that ß-cell proliferation can compensate for any losses. Such a subclinical autoimmune process may at a later stage result in slowly progressive type 1 diabetes or latent autoimmune diabetes in adults (21,22). The histopathology of late-onset type 1 diabetes has not been well studied. One case has been described: A 65-year-old female with positivity for two aAbs (GADA and IA-2A) and a HLA-DQ/DR risk profile was initially diagnosed with type 2 diabetes and then shown to present several islets with predominantly CD4+ T-cell infiltrates, without signs of ß-cell destruction (23). In the presently described cases, infiltrating leukocytes mainly corresponded to CD8+ T-cells and CD68+ macrophages, as was also the case in type 1 diabetic patients with insulitis (2,24–26). Our data do not strengthen or weaken the significance of the detected circulating markers as predictors for type 1 diabetes. They indicate an association between triple antibody positivity with a high-risk genotype and an insulitis process in the pancreas. In elder individuals, this insulitis process appears limited to <10% of the islets and may thus not lead to type 1 diabetes or may lead only to a mild form. We cannot exclude that cases with a low percentage of infiltrated islets were missed as a result of our sampling in one region (body) and of the relatively small number of analyzed islet sections (averaging 180 islets per organ); more extensive sampling was precluded by the islet isolation procedure for which these organs were harvested. For the same reason, we may have missed differences in ß-cell mass if these would have occurred in other regions. Despite the limitations imposed by the small tissue specimen, the nature and extent of our study provide information with respect to the use of organs from adult aAb+ donors for transplantation. Absence of histopathological changes in all 59 donors with one or two aAbs questions exclusion of these organs, while the detection of insulitis in triple antibody+ donors can be seen as an exclusion criterion. In conclusion, we have screened 62 nondiabetic aAb+ organ donors older than 25 years for the presence of insulitis. Insulitis was found in two of the three case subjects who presented at least three antibodies but in none of the other 59 antibody+ subjects or 62 matched controls. Presence of one or more antibodies was not related to a decrease in ß-cell mass. These observations can be used to include or exclude organs from aAb+ donors for transplantation in diabetic recipients. They also need consideration when recruiting adult aAb+ subjects for prevention trials.
This study has received grants from the Research Foundation Flanders (G035803 and G051704) and a Center Grant from the Juvenile Diabetes Research Foundation (4-2001-434). We thank Nicole Buelens, Violeta Ardelean, Kristien Van Belle, Sylvie Duys, and Patrick Goubert for expert technical assistance. Crystalline humulin was a gift from Dr. H. Schmitt (Eli Lilly and Co.), cDNA for GAD65 was a gift from Dr. Å. Lernmark (University of Washington, Seattle, WA), and cDNA for IA-2ic was a gift from Dr. M. Christie (King's College, London, U.K.).
Published ahead of print at http://diabetes.diabetesjournals.org on 11 June 2007. DOI: 10.2337/db07-0416. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Received for publication March 26, 2007 and accepted in revised form June 3, 2007
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