T-cells come into contact with CCL2⁺ perivascular astrocytes in the areas of infiltration.

<p>(A) CCL2 is highly expressed in perivascular astrocytes where T-cells infiltrate the brain tumor. Detailed confocal analysis of samples of gliomas revealed that tumorigenic areas show CCL2-expressing astrocytes (red) with infiltration of CD3⁺ T-cells (green). Nuclei are stained with DAPI (blue). (B) Infiltration of T-cells occurs throughout multiple anatomical contacts between T-cells and CCL2-expressing astrocytes. Image B1 shows numerous CD3⁺ T-cells (green) establishing specific contacts with CCL2⁺ cells (red). In pictures B2, 3 and 4, a detail of T-cells (green) in contact with CCL2 perivascular astrocytes. Image B4 shows a specific detail of a CD3/CCL2 contact on the xy axis and the two lateral views on the z axis. (C) Confocal analysis of a CD3⁺ T-cell coming into contact with a CCL2⁺ cell located at the perivascular area of adenoviral injected monkey brain. The three dimensional transparency (Composite) of a stack of images shows a CD3⁺ T-cell (green), in close apposition to the endothelium, marked with Col-IV (red), and contacting a CCL2⁺ cell (magenta). A detail of the CD3-CCL2 contact is also shown in a 0.5 µm optical section on the xy axis and the two lateral views on the z axis. (D) Diagram showing how T-cells may come into contact with CCL2-expressing astrocytes in the edge of BVs suggesting that CCL2⁺ astrocytes contribute to the extravasation of T-cells in the brain parenchyma.