The BB Diabetic Rat: Profound T-Cell Lymphocytopenia

Abstract

SUMMARYApproximately 50% of Wistar "BB" rats spontaneously develop overt diabetes mellitus characterized by loss of /3-cells and "insulitis." To define abnormalities of immunoregulation in these rats, we quantitated their major circulating lymphocyte subsets. Independent of the development of diabetes, we found the BB rats to have a markedly increased percentage of circulating B lymphocytes which is secondary to a severe T-cell lymphocytopenia, with the major circulating T-cell subset reacting with monoclonal antibody W3/25 markedly decreased. This lymphocytopenia is present in every animal studied and contrasted with studies of the nondiabetic Wistar strain from which the "BB" rats were developed. DIABETES 30:887-889, October 1981. T he spontaneously diabetic Wistar rat (the "BB rat") has become an important animal model of type I insulin-dependent diabetes mellitus. -2Approximately 50% of these nonobese outbred Wistar rats between 60 and 120 days of age develop severe hyperglycemia associated with /3-cell depletion, insulitis, and ketoacidosis. Of major importance is the finding of Like et al. that various immunosuppressive regimens (including administration of anti-lymphocyte globulin) can prevent the onset of overt diabetes in these animal.3 -4 It is postulated that the development of diabetes mellitus is secondary to inherited abnormalities of immunologic function. In this report we describe our findings that all BB rats, independent of the development of overt diabetes, have a specific deficiency of T-cells reacting with monoclonal antibody W3/25. METHODSNineteen rats of the BB strain and 20 rats of the control, nondiabetic Wistar strain (male and female) were kindly provided by Dr. P. Thibert. Rats were screened for glucosuria using Testape (Eli Lilly and Company, Indianapolis, Indiana) approximately every 3 days, and plasma glucose was measured using a Beckman glucose analyzer (Beckman Instruments, Fullerton, California) at least once a week. The onset of diabetes was abrupt in the six animals that became diabetic. Plasma glucose at the time of diagnosis of diabetes ranged from 284 to 649 mg/dl. Approximately every 2 wk, animals were gently anesthetized with ether, and 1 ml of blood was withdrawn from a tail vein into heparinized tubes for determination of white blood count, differential and lymphocyte subsets. White blood count was determined using a Coulter Zf counter and differential using Wright's stained slides. Peripheral white blood cells were then applied to a Ficoll-Hypaque gradient (24:10 v,v; 9% Ficoll 400:34% Hypaque M) and the lymphocytes and monocytes present at the interface of the gradient were harvested. This lymphocyte fraction was then incubated at 37°C for 45 min to remove cytophilic immunoglobulin, and then reacted with rhodamine conjugated F (ab') 2 anti-rat antibody (Cappel) at 4°C for 45 min, followed by three washes with phosphatebuffered saline containing 1% bovine albumin. To determine the percentage of B lymphocytes, the number of cells with rim fluorescence was determined usi...

Prevention of Diabetes in BB Rats: I. Evidence Suggesting a Requirement for Mature T Cells in Bone Marrow Inoculum of Neonatally Injected Rats

“…For both ConA stimulation assays and MLR assays, T cell growth factor (TCGF) was added to enhance the normally blunted BB response (see ref. 10; and unpublished observations). Supernatant from ConA-stimulated rat splenic lymphocytes was used as a source of TCGF after removal of ConA by passage over Sephadex G-50.…”

T-Lymphopenia and T-Cell Imbalance in Diabetic db/db Mice

“…40 Conversely, antibody synthesis in vitro is not altered. 30 The early and sustained T-lymphopenia in db/db mice is reminiscent of that in NOD mice, 41 BB rats, 42 and diabetic dogs. 43 The increase in the Lyt1 + /Lyt2 + ratio is also a reminder of the subset imbalance detected in BB rats 4445 and in recent-onset diabetic subjects, 13 -21 although this imbalance is transient 1618 and not constantly detected 141819 in human subjects.…”

Rat Models of Type 1 Diabetes: Genetics, Environment, and Autoimmunity

“…The most obvious and problematic immunopathology in all spontaneously diabetic BB rats is profound T cell lymphopenia (Elder and Maclaren 1983;Yale et al 1985). This condition is characterized by a severe reduction in the number of CD4 + T cells (Jackson et al 1981) and nearly complete absence of the CD8 + T cell subset (Jackson et al 1983;Poussier et al 1982;Woda et al 1986). The rats are also severely deficient in ART2 + T cells.…”