Chronic neuroinflammation in the frontal cortex of a patient with Lyme neuroborreliosis. First column (A, D and G): Accumulation of HLA-DR (A) and CD68 (D) immunoreactive microglia forming clumps, and GFAP (G) positive large reactive astrocytes in the frontal cortex of a patient with Lyme neuroborreliosis. Second column (B, E, H) : On frontal sections of the control patient, activated microglia or astrocytes are not visible. Some resting microglia showing weak HLA-DR immunostaining (B), absence of CD68 immunoreaction (E) and weak GFAP immunostaining of non reactive astrocytes and astrocytic processes (H) are visible. C, F and I: Absence of immunoreaction on sections of a patient with Lyme neuroborreliosis where immunostaining was performed with omission of the anti-HLA-DR (C), anti-CD68 (F) and anti-GFAP (I) antibodies. Bars: A, B, F, H, I = 150 μm; C, D, E = 120 μm; G = 100 μm.