Abstract
There is recent in vitro evidence that human neurons express the innate immune response receptor, Toll-like receptor-3 (TLR-3), and that expression is enhanced in viral infections. The authors examined the immunohistochemical expression of TLR-3 in the cerebellar cortex of postmortem human brains. Purkinje cells were found to express TLR-3 in all cases of rabies (4 of 4) and herpes simplex encephalitis (2 of 2) as well as in cases of amyotrophic lateral sclerosis (1 of 2), stroke (1 of 2), and Alzheimer's disease (3 of 3). In cases of viral infection, direct viral infection was not necessary for enhanced neuronal TLR-3 expression, suggesting that soluble factors likely play an important role in inducing TLR-3 expression. In addition to neurons, occasional Bergmann glia expressed TLR-3 in some cases. This study has provided evidence that human brain neurons can express TLR-3 in vivo and suggests that neurons may play an important role in initiating an inflammatory reaction in a variety of neurological diseases. Journal of NeuroVirology (2006) 12, 229–234.
Alan C. Jackson was on sabbatical leave from Queen's University.
The authors are grateful for expert technical assistance by Huot Khun (Unité d'Histotechnologie et Pathologie, Institut Pasteur) and for the gift of monoclonal antibody HAM from Dr. Reto Zanoni (Swiss Rabies Center, Institut of Veterinary Virology, Bern, Switzerland). This work was supported by institutional grants from Institut Pasteur (M. Lafon) and Canadian Institutes of Health Research grant MOP-64376 (A.C. Jackson).