PHENOTYPIC AND QUANTITATIVE CHANGES IN MAST-CELLS AFTER SYNGENEIC UNILATERAL LUNG TRANSPLANTATION IN THE RAT

1. Lung transplantation causes a total interruption of the innervation and vascularization within the transplanted organ, followed by repair processes, This is frequently associated with bronchial hyperresponsi veness, A common feature of tissue repair is an increase in the number of mast cells, Three phenotypically distinct mast cell subsets, with respect to their protease content, have been identified in rat lung, a nd it is probable that mast cells of differing protease phenotype fulf il different functions. 2. We have compared the number, protease pheno type and distribution of mast cells in left lung from transplanted and control Lewis rats 1 month after syngeneic unilateral left lung trans plantation, without interference of inflammation, graft rejection or o f any treatment, Connective and mucosal-type mast cell phenotypes were characterized using antibodies directed against their specific rat ma st cell proteases, RMCPI and RMCPII, respectively. 3. After transplant ation, RMCPI and RMCPII tissue concentrations increased by 172% and 23 9%, respectively, compared with controls (13.1+/-1.2 and 5.6+/-1.0 mu g/g). 4. Localization of mast cell phenotypes was studied by immunohis tochemistry after double immunostaining, The number of mast cells incr eased after transplantation: the increase in the number of RMCPI-immun oreactive mast cells (RMCPI(+)) was significant around bronchioles and arterioles, around large vessels and in the pleura, The number of RMC PII(+) mast cells also significantly increased around bronchioles and arterioles, as well as in the smooth layer large airways, Some mast fo r presence of both RMCPI and RMCPII, supporting the existence of co-ex pressing phenotype in rat lung, The number of mast cells of the RMCPI( +)/II+ phenotype significantly increased around bronchioles and arteri oles and in the pleura, Moreover, the distribution of the mast cell ph enotypes was modified in the different areas after transplantation. 5. This indicates a local differentiation/maturation of mast cells after transplantation.