Blocking PD-L1/2 enhances migration of CD8 and CD4 T cells through an in vitro BBB model. HBECs were plated to the upper chamber of a Boyden chamber and then inflamed. Activated CD8 (A, B) and CD4 (C, D) T cells were added to the upper chamber and allowed to migrate for 24 hours in the presence of an isotype control antibody or blocking antibodies specific for PD-L1 and PD-L2. A-C. Graphs representing the number of CD8 (A) or CD4 (C) T cells migrating through the in vitro BBB for 3-5 distinct T cell donors on 2-3 HBECs preparations. Student's t-test: ** P < 0.01. B-D. Graphs representing the percentage of BSA-FITC diffusion as a measure of permeability of the in vitro BBB, showing one representative experiment out of three.