EXPRESSION OF MAJOR HISTOCOMPATIBILITY ANTIGENS IN HUMAN CHRONIC-PANCREATITIS

T-lymphocytic infiltration of the exocrine pancreas and liver in patie nts with chronic pancreatitis has suggested that cell mediated immune mechanisms may play a part in the pathogenesis of this disease. As exp ression of major histocompatibility (MHC) antigens is a prerequisite f or organ specific autoimmunity, the expression of HLA class I (beta2-m icroglobulin) and class II (HLA-DR) determinants have been analysed, t ogether with the presence of T-lymphocytes, in 93 patients (64 men and 29 women, mean age 40.6 years) having an operation for chronic pancre atitis. Ethanol (63 patients), recurrent acute pancreatitis (12), cong enital lesions (2), and unknown (16) were suggested to be the causes o f the disease. Immunohistochemical staining of formalin fixed and para ffin wax embedded tissue sections used conventional immunohistochemica l techniques with specific anti-serum samples. No MHC expression was i dentified in 10 histologically normal pancreatic control specimens or in four cases of chronic pancreatitis secondary to obstruction by neur oendocrine tumours within the head of the pancreas. Beta2-microglobuli n expression by pancreatic exocrine epithelial cells was seen in 76 ch ronic pancreatitis specimens (82%) while HLA-DR was present in 61 (66% ). Simultaneous expression of both class I and II determinants was see n in 53 (57%) of cases. MHC determinant expression was not found in 10 cases (11%) of chronic pancreatitis. In the positive specimens, expre ssion was confined to ductal and ductular (interlobular and intralobul ar) epithelium with no staining of acinar cells. Staining was not rela ted to the suspected cause of the disease or age. T-lymphocytes were m ore prominent in chronic pancreatitis mean (SEM) (131 (15) cells per h igh powered field) than controls (5 (1), p<0.01). Aberrant MHC express ion by exocrine pancreatic ephithelial cells occurring in the presence of an appreciable T-cell infiltration confirmed that the appropriate cellular conditions were present for cell mediated cytotoxicity to con tribute to the pathogenesis of chronic pancreatitis.