An immunofluorescence study of anti-pancreatic islet cell antibodies in the spontaneously diabetic BB Wistar rat

Abstract

Summary. Sera from BB Wistar rats and Wistar control rats were evaluated for the presence of islet cell antibodies in a prospective study using an indirect immunofluorescence assay on pancreatic islet cell suspensions from cultured rat islets. Islet cell surface antibodies were detected in sera from all animals of the spontaneously diabetic BB Wistar rat colony. The antibody could be detected well before the clinical onset of the disease and was present throughout the course of study of all diabetic animals. Sera from control Wistar rats were negative when tested for this antibody.Key words: Islet cell surface antibody, BB rat, immunofluorescence, islet culture, cell suspension, pre-diabetes.A number of investigators have reported antibodies in the sera of patients with insulin-dependent diabetes [1][2][3][4][5]. These earlier studies tested a human serum reaction on frozen or fixed sections from blood group 0 cadaveric donor pancreases. This islet cell antibody is reported to bind cytoplasmic antigens only [6,7], and is found in 60%-85% of newly diagnosed patients with insulin-dependent diabetes. The percentage of patients with detectable levels of circulating islet cell antibodies decreases with time [8].More recently, an islet cell surface antibody has been detected in the sera of diabetic patients [6,9]. Islet cell surface antibody is detected in a majority of insulindependent diabetic patients ( > 60%) and is reported to lyse fl cells specifically from newborn rat islets. However, islet cell surface antibody is not diagnostic of insulin-dependent diabetes as it is found also in a significant proportion of first degree relatives (25 %).The spontaneously diabetic BB Wistar rat presents a syndrome with many analogies to the development and expression of insulin-dependent diabetes in man [10,11]. We have been interested in it as a model for examining the role that antibodies to pancreatic islet cells might play in the aetiology of insulin-dependent diabetes, with particular reference to the questions: (1) does the diabetic rat have a circulating antibody specific for a pancreatic islet cell but not present in the normal rat? and (2) if so, does the presence of this antibody precede the onset of the disease? We report here the results of an immunofluorescence study aimed at answering these questions. Materials and Methods Animals and SeraThe BB rat is maintained in our laboratories as a random-bred, closed colony. Animals are kept in an air-conditioned room (20 ~ 50% relative humidity) with a 12-h light/dark cycle, and fed Purina Lab Chow 5001 and water ad libitum. Urinary glucose levels are determined daily on all BB rats using the glucose enzymatic test strip (Tes-Tape, Eli Lilly, Toronto, Canada). Individual rats are classified as diabetic on the basis of a positive glycosuria and they are subsequently maintained on daily PZ1 insulin. At the time of this study the incidence of diabetes in the colony was 70% and the average age of onset 85 days.Eleven diabetic BB rats from seven litters, all diagnosed as diabe...

Time Course of Serum Glucoregulatory Variables and Lipids following Neonatal Thymectomy of Diabetes-Prone and Control BB Wistar Rats Fed a Defined Diet

“…Marliss et al [2] have pointed out that genetically susceptible rats may be potential diabetics even though they do not display symptoms during the period of obser vation. This concept is supported by findings that at least some (10-25%) asymptomatic, littermate 'controls' have insulitis and glu cose intolerance [2,11], major T cell defects [8,9], islet cell surface antibodies [12], spora dically elevated plasma glucagon (see below), and altered tissue levels of alpha-and gam ma-tocopherol [W. Behrens et al, submitted for publication].…”

Maternal and Fetal Endocrine Pancreas in the Spontaneously Diabetic BB Rat

“…The occurrence of diabetes is determined by genetic factors [15] but the diet also influences the ultimate incidence [26], Insulitis is present at onset of diabetes, but later on B cells almost completely disap pear [7], In this study, maternal diabetic BB rats were practically devoid of B cells and islets consisted only of glucagon-and soma tostatin-containing cells (PP cells were not examined). B-cell-specific surface anti bodies were present in more than half of diabetic rats; the lower frequency of ICSA in diabetic BB rats in this series compared to other [8][9][10] must be ascribed to the later age of onset in the Leuven colony and the ICSA technique, which detects surface anti bodies at a moment when they are known to exhibit maximal binding and cytotoxicity [ 12].…”

“…The diabetes is autoimmune: both cellular and humoral au toimmunity are involved [15]. ICSA are present and have been related to the B cell destruction [8][9][10][11][12]; autoantibodies to a 64-kilodalton islet cell protein have been char acterized [23], but, in contrast to human IDDM, islet cytoplasmic antibodies are not present [24,25]. Other antibodies against nonislet cells and lymphocytes have also been detected [8,24,25].…”

“…The clinical onset of diabetes is abrupt with histological evidence o f 'insulitis', which after a few days develops into a virtual absence of B cells. Severely ketotic, moderately ketotic and sta ble diabetic rats have been characterized ac cording to the degree of insulin deficiency and ketonemia [6,7], Islet cell surface antibodies (ICSA) are present in the majority of diabetic BB rats and have been related to the B cell destructive process and B cell dysfunction [8][9][10][11][12]. Diabetes-prone BB rats are characterized by a T cell lymphopenia from birth [13,14]; a T cell depletion is present in the white pulp of the spleen and the cortical areas of lymph nodes of adult diabetic BB rats, while the thy mus was reported to be normal [13,15].…”

Experimental Models of Type-I Diabetes

“…Anti-islet cell autoantibodies are detected in the serum of BB rats at an early age, before the onset of diabetes. Paradoxically, the islet cell cyto plasmic antibodies (ICA) that are the hall mark of human IDDM are not found in BB rats [34,36,37], Anti-islet cell autoantibod ies can however be detected against surface determinants using different techniques: in direct immunofluorescence [38][39][40], radiola beled protein-A-binding assay [36,41,42], immunoenzymology (ELISA), cytotoxicity in the presence of complement on 5,Crlabeled islet cells [43] or inhibition of insulin release by glucose-stimulated islets [43]. Anti-islet antibodies are usually found in a majority of diabetic rats with peak values at the time of diabetes onset (titers tending to decrease thereafter).…”