Figure 6.

Immunohistochemistry of human PD midbrain tissue samples stained for P. acnes (green; A+B), neuronal microtubules (MAP2; red; A) and nuclei (DAPI; blue; A+B). Age-linked lipofuscin auto-fluorescence was extinguished with Sudan Black B. Presence of P. acnes (arrow) in the periplasmic space of a human neuron (A) between nucleus (n) and cytoskeleton; or neutrophil (B) with its characteristic multi-lobed nucleus inside a midbrain capillary (Cap). These findings are typical for PD and absent in most control sections. Retrograde movements along cranial nerves, trauma-induced micro-bleeds as well as the newly discovered glymphatic system represent potential microbial pathways into the CNS.