Histopathological evaluation and immunofluorescence staining of lesions in the brain, dorsal root nerves and DRG. A) Composite light microscope image of leptomeningitis in the brain of a B. burgdorferi-inoculated animal (DR50) showing lymphocytic, plasmacytic and monocytic infiltration by hematoxylin and eosin staining, as well as immunohistochemical staining showing CD3-labeled T cells, CD-20-labeled B cells, and CD68-labeled macrophages. B) Confocal micrograph showing immunofluorescence staining of CD3-labeled T cells (green), CD20-labeled B cells (blue) as well as CD68-labeling macrophages (red) in a representative inflammatory lesion from the meninges of animal DR50. C) FITC-labeled B. burgdorferi antigen (green) in the vicinity of CD3-staining T cells (red) and CD68-staining macrophages in lesions found in the frontal cortex of animal DR50. D) Radiculitis in the dorsal root of a cervical spinal nerve proximal to the ganglion of animal DH50. There is abundant lymphocytic, and monocytic infiltration as well as plasma cells. A few adjacent nerve fibers have swollen sheaths. E) Chronic-type inflammation of DRG from animal DH50 showing infiltrates of lymphocytes, plasma cells, and monocytes. F) B. burgdorferi antigen stained with antibody to B. burgdorferi labeled with FITC, in the vicinity of the CD3-staining T cells (red) in lesions found in DRG of animal DR50.