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Down regulation of Platelet Endothelial Cell Adhesion Molecule-1 (PECAM-1) in Schistosome but not Tuberculosis granuloma models.
1Maklad S., 2El-Essawy A., 2Abu Shady M. and 1El-Sheikh N.
1Departments of Microbiology, Faculty of Medicine for Girls, Al-Azhar University and 2Faculty of science, Ain Shams University.

It has been shown that granuloma reaction in tuberculosis (TB) is mainly associated with Th1 cytokine expression while that in schistosomiasis (Schistosome) is Th2 dependent. On the other hand adhesion molecules which regulate leukocyte activation and migration are influenced by these cytokines. The aim of the study was to compare the expression of intercellular adhesion molecule-1 (ICAM-1) and the platelet endothelial cell adhesion molecule-1 (PECAM-1), and net granuloma area in the two reactions. The granuloma models were established in the lung of presensitized CD1 mice. In the TB model presensitization was carried out using the Bacillus Calmette Guérin (BCG) vaccine while in schistosome model, attenuated S.mansoni cercariae vaccine was used. This was followed by intravenous injection of sepharose beads coated with purified protein derivatives (PPD) and soluble egg antigen (SEA) in the TB and schistosome models respectively. Cryostat lung sections were analyzed for the expression of ICAM-1 and PECAM-1 using image analyzer by calculating the percent video count areas of tissue that express positive signals. In both models, animals received Ag coated beads demonstrated significant increase in ICAM-1 expression as compared to uncoated beads (p<0.001) and naïve animals (p<0.001). In contrast PECAM-1 expression was down-regulated in the schistosome model while in the TB model, no significant difference was found between vaccinated and control animals. Morphometric analysis revealed that the net granuloma areas in the TB (19962 +1847) was not significantly different from the schistosome (17934+1259) model and that in the later model the granuloma size of naïve/challenged (25948+1854) animals was significantly larger than the vaccinated/challenged animals (p< 0.001). In conclusion, this study supports the view that different cytokine regulatory mechanisms might be involved in the two granuloma reactions and that the down regulation of PECAM-1 expression in schistosome model is probably mediated by the dominating Th2 cytokine response.

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Copyright 2002 Egyptian Association of Immunologists .
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