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

To test the hypothesis that lymphocyte infiltration in brain arteriovenous malformation (bAVM) is not associated with iron deposition (indicator of microhemorrhage).

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.

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 interval =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.

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.