[Lack of stimulation of CD11b/CD18 induced leukocyte adhesioin by platelet activating factor (PAF) and f-MLP in malignant tumor endothelium in experimental pancreas cancer of the rat].
The interaction between immunocompetent cells and tumor-endothelium is essential for effective immunologic recognition. In the present study we evaluated resting and CD11b/CD18-mediated leukocyte adhesion on tumor-endothelium of experimental pancreatic carcinoma and in healthy pancreatic venules.


METHODS
22 male Lewis rats (120-140 g) were anesthetized. Duct-like pancreatic carcinoma (DSL6A, Am. J. Pathol. 1993; 143:292) was induced by intrapancreatic implantation of tumor fragments between inert polymethylmetacrylat plates. After 4 wks the tumor-bearing pancreas was exposed and the microcirculation studied. Parameters in tumor vessels (15-40 microns) and healthy pancreatic collecting venules (20-40 microns) included: Erythrocyte velocity, Leukocyte adhesion, Vessel diameter and wall shear rate. Measurements were obtained before and 5 min after adding f-MLP (100 mM) or PAF (50 mM), two CD11b/CD18 agonists of different potency to the immersion chamber.


RESULTS
[table: see text]


CONCLUSIONS
In experimental pancreatic carcinoma leukocyte adhesion of low affinity is reduced despite comparable wall shear rates. The CD11b/Cd18-mediated adhesion of high affinity, which is inducible by f-MLP and PAF in healthy pancreatic venules, is absent in tumor vessels. This may be a mechanism by which malignant tumors escape immune control.
D000818:Animals; D001783:Blood Flow Velocity / Q000187:drug effects / Q000276:immunology; D039481:CD11b Antigen / Q000502:physiology*; D018821:CD18 Antigens / Q000502:physiology*; D021441:Carcinoma, Pancreatic Ductal / Q000098:blood supply / Q000276:immunology*; D002448:Cell Adhesion / Q000187:drug effects* / Q000502:physiology; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000276:immunology; D007962:Leukocytes / Q000187:drug effects* / Q000502:physiology; D008297:Male; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology*; D009368:Neoplasm Transplantation; D010190:Pancreatic Neoplasms / Q000098:blood supply / Q000276:immunology*; D010972:Platelet Activating Factor / Q000494:pharmacology*; D051381:Rats; D011917:Rats, Inbred Lew
D039481:CD11b Antigen; D018821:CD18 Antigens; D010972:Platelet Activating Factor; D009240:N-Formylmethionine Leucyl-Phenylalanine