Distinctive distribution of lymphocytes in unruptured and previously untreated brain arteriovenous malformation

Aim:To test the hypothesis that lymphocyte infiltration in brain arteriovenous malformation(bAVM)is not associated with iron deposition(indicator of micro-hemorrhage).Methods:Sections of unruptured,previously untreated bAVM specimens(n=19)were stained immunohistochemically for T-lymphocytes(CD3+),B-lymphocytes(CD20+),plasma cells(CD138+)and macrophages(CD68+).Iron deposition was assessed by hematoxylin and eosin and Prussian blue stains.Superficial temporal arteries(STA)were used as control.Results:Both T-lymphocytes and macrophages were present in unruptured,previously untreated bAVM specimens,whereas few B cells and plasma cells were detected.Iron deposition was detected in 8 specimens(42%;95%confidence intervals=20-67%).The samples with iron deposition tended to have more macrophages than those without(666±313 vs.478±174 cells/mm2;P=0.11).T-cells were clustered on the luminal side of the endothelial surface,on the vessel-wall,and in the perivascular regions.There was no correlation between T-lymphocyte load and iron deposition(P=0.88).No macrophages and lymphocytes were detected in STA controls.Conclusion:T-lymphocytes were present in bAVM specimens.Unlike macrophages,the load and location of T-lymphocytes were not associated with iron deposition,suggesting the possibility of an independent cell-mediated immunological mechanism in bAVM pathogenesis.