An experimental model of autoimmune pancreatitis in the rat

Abstract

Autoimmune pancreatitis (AIP), a recently defined disease of unknown etiology, is characterized by inflammatory infiltrates in the pancreas with conspicuous involvement of the ducts. The disease clinically manifests in humans as epigastric pain, weight loss, and jaundice. This report describes the development of a novel animal model of this disease in the rat, which we have termed experimental autoimmune pancreatitis. Adoptive transfer of amylase-specific CD4(+) T cells was able to confer pancreatitis to naive syngeneic recipient animals. No treatments before the adoptive transfer of T cells were necessary for disease to ensue, and the severity of disease was proportional to the number of T cells administered. The pancreatic lesions of rats with experimental autoimmune pancreatitis were characterized histologically as overwhelmingly lymphocytic with occasional plasma cells, neutrophils, and mast cells. Acinar tissue destruction and ductular inflammation were common features, with less frequent involvement of larger ducts. Immunohistochemical analysis revealed the presence of CD4(+) T cells in large numbers as well as CD8(+) T cells, macrophages, and dendritic cells. Expression of MHC I and MHC II also increased at the site of the lesion. Clinically, the disease manifested as either failure to gain weight at a rate concomitant with control animals or as outright weight loss. Thus, administration of activated CD4(+) T cells specific for the pancreatic enzyme amylase can induce pancreatitis in the rat in a manner that is reminiscent of human AIP.

Figure 1

DA(RP) (a) or Lewis (b) anti-amylase T cell lines were evaluated for antigen specificity in a proliferation assay using syngeneic antigen-presenting cells and varying concentrations of antigen. c: DA(RP), RT1.A^aB/D^l, were stimulated with varying concentrations of amylase in the presence of Lewis, RT1.A^lB/D^l, antigen-presenting cells to confirm MHC II restriction of the T cells. Vertical axes represent ³H-thymidine incorporation in dividing cells. Results are expressed as cpm ± SD.

Figure 2

DA(RP) (a) or Lewis (b) rats received syngeneic activated anti-amylase T cells at the indicated dosages and were followed daily for weight change. Data are presented as percent weight change as compared to the initial weight on day 0.

Figure 3

H&E staining of pancreata from animals given activated anti-amylase T cells. a: DA(RP) given 75 × 10⁶ T cells and sacrificed on day 10. Section demonstrates diffuse lobular tissue destruction. b: DA(RP) given 30 × 10⁶ T cells and sacrificed on day 32. Section demonstrates an inflamed ductule. c: Same animal as depicted in a demonstrating acinar tissue destruction as well as periductal mast cells. d: DA(RP) given 75 × 10⁶ T cells and sacrificed on day 10 (different animal from that depicted in a). Section demonstrates periductal inflammation. e: Lewis rat given 75 × 10⁶ T cells and sacrificed on day 15. Section demonstrates periductal inflammation in the Lewis rat. f: Lewis rat given 100 × 10⁶ T cells and sacrificed on day 15. Section demonstrates neutrophils infiltrating the duct wall. g: Lewis rat given 50 × 10⁶ T cells and sacrificed on day 28. Section demonstrates apoptotic bodies at the site of the lesion. h: Same animal as depicted in g. Section demonstrates mast cells in the pancreas-associated lymph node. i: Same animal depicted in d. Sample depicts inflammation surrounding an islet. Original magnifications: ×10 (a, c); ×40 (b, d, g); ×20 (e, h, i); ×60 (f).

Figure 4

Immunohistochemical analysis of serial sections of an inflamed pancreas from a Lewis rat given activated anti-amylase T cells 16 days previously. This series of sections demonstrates an inflammatory lesion focused on a pancreatic duct. a: Anti-αβ TCR, R7.3; b: anti-CD4, W3/25; c: anti-CD8, OX-8; d: anti-B cell, RLN.9D3; e: anti-CD11b, OX-42; f: anti-CD163, TLD-1F5; g: anti-CD11c, 8A2; h: anti-NK cell, 3.2.3; i: anti-MHC II, OX-6; j: anti-MHC I, OX-18.

Figure 5

DA(RP) anti-CAII (a) and anti-LF (b) T cells were evaluated for antigen specificity in a proliferation assay using syngeneic antigen-presenting cells and varying concentrations of antigen. Vertical axes represent the ³H-thymidine incorporation in dividing cells. Results are displayed as cpm ± SD. c: Histological section of a pancreas from a DA(RP) rat given anti-CAII cells. d: Histological section of a DA(RP) rat given anti-LF cells. Original magnifications, ×20.