Choroid plexus selectively accumulates T-lymphocytes in normal controls and after peripheral immune activation

We determined T-lymphocyte migration into brain and choroid plexus (CPx) after enterotoxin-induced systemic immune activation. CPx T-lymphocytes/mm2 in control mice were >3 logs more numerous than brain and increased by as much as 150-fold by post-enterotoxin Day 3 (p<0.01). Flow cytometry of pooled CPx confirmed post-enterotoxin increases. Brain T-lymphocytes increased up to 17-fold after SEB and accumulated in subependymal and periventricular brain. T cell apoptosis was absent. These results show preferential T-lymphocyte migration to CPx over brain and suggest that brain T cells may be derived from the CPx by direct migration or by cerebrospinal fluid dissemination.