Autoimmune maintenance and neuroprotection of the central nervous system

Vaccination for neuroprotection in the mouse optic nerve: implications for optic neuropathies

T-cell autoimmunity to myelin basic protein was recently shown to be neuroprotective in injured rat optic nerves. In the present study, using the mouse optic nerve, we examined whether active immunization rather than passive transfer of T-cells can be beneficial in protecting retinal ganglion cells (RGCs) from post-traumatic death. Before severe crush injury of the optic nerve, SJL/J and C3H.SW mice were actively immunized with encephalitogenic or nonencephalitogenic peptides of proteolipid protein (PLP) or myelin oligodendrocyte glycoprotein (MOG), respectively. At different times after the injury, the numbers of surviving RGCs in both strains immunized with the nonencephalitogenic peptides pPLP 190-209 or pMOG 1-22 were significantly higher than in injured controls treated with the non-self-antigen ovalbumin or with a peptide derived from beta-amyloid, a non-myelin-associated protein. Immunization with the encephalitogenic myelin peptide pPLP 139-151 was beneficial only when the disease it induced, experimental autoimmune encephalomyelitis, was mild. The results of this study show that survival of RGCs after axonal injury can be enhanced by vaccination with an appropriate self-antigen. Furthermore, the use of nonencephalitogenic myelin peptides for immunization apparently allows neuroprotection without incurring the risk of an autoimmune disease. Application of these findings might lead to a promising new approach for treating optic neuropathies such as glaucoma.

DNA recombination as a possible mechanism in declarative memory: a hypothesis

The durability of declarative memory suggests that it has either a chemical or a structural basis. Current models of long-term memory are based on the general assumption that traces of memory are stored by structural modifications of synaptic connections, resulting in alterations in the patterns of neural activity. Changes in gene expression, regulated at both the transcriptional and the translational levels, are considered essential for structural synaptic modifications. Here we present an alternative hypothesis stating that permanent memory has a chemical rather than a structural basis. We suggest that the mechanism of memory coding in the brain is similar to that in the immune system so that the permanence of memories in the nervous system is ensured at the genomic level by a somatic recombination mechanism. Thus, we hypothesize that traces of permanent declarative memory might present within cerebral neurons in the form of novel proteins coded by the modified genes. This discussion is intended to provide evidence in support of a DNA recombination mechanism for memory storage in the brain and to stimulate further research working toward the evaluation of this hypothesis.

Autoimmunity can benefit self-maintenance

Autoimmunity is usually considered only as a cause of disease; nevertheless, human T-cell repertoires are filled naturally with autoimmune lymphocytes. Here, we review evidence that autoimmune T cells can help heal damaged tissues, indicating that natural autoimmunity could also be a cause of health.