APOPTOTIC ELIMINATION OF V-BETA-8.2(-NERVOUS-SYSTEM DURING RECOVERY FROM EXPERIMENTAL AUTOIMMUNE ENCEPHALOMYELITIS INDUCED BY THE PASSIVE TRANSFER OF V-BETA-8.2(+) ENCEPHALITOGENIC T-CELLS() CELLS FROM THE CENTRAL)

A CD4(+)V beta 8.2(+) T cell clone specific for the peptide 72-89 of g uinea pig myelin basic protein (GMBP) Was used to induce acute experim ental autoimmune encephalomyelitis (EAE) in Lewis rats. To assess apop tosis in inflammatory cells infiltrating the central nervous system (C NS), we extracted cells from the spinal cord, enriched them for T cell s and performed now-cytometric analysis of their DNA stained with prop idium iodide. The presence of apoptosis was confirmed by the demonstra tion of DNA fragmentation on gel electrophoresis. A gradual increase i n the proportion of apoptotic cells was observed between 4 and 7 days after the transfer of the encephalitogenic T cells. The highest freque ncy of apoptotic cells (9.2 +/- 1.2%) was observed 7 days after cell t ransfer, when clinical recovery commenced. Passive transfer of ovalbum in-specific cells resulted in only a background level (0.8%) of apopto sis in the CNS. We conclude that the apoptotic process selectively eli minates autoreactive T cells from the CNS as: (a) there was a selectiv e disappearance of disease-relevant CD5(+)V beta 8.2(+) cells from the CNS during the course of EAE; (b) there was a decrease in the frequen cy of CNS-infiltrating T cells reactive to the GMBP 72-89 peptide duri ng the course of EAE, and in a standard proliferation assay there was a loss of in vitro reactivity of CNS-infiltrating cells to this peptid e, but not to a non-CNS antigen (ovalbumin); (c) simultaneous surface labeling and DNA analysis of CNS-infiltrating cells revealed that the frequency of V beta 8.2(+) cells was about sevenfold higher in the apo ptotic T cell population than in the normal (non-apoptotic) T cell pop ulation; and (d) we were unable to detect recirculation of the V beta 8.2(+) cells to lymphoid organs after their frequency decreased in the CNS. The selective apoptotic elimination of autoreactive T cells from the target organ of this spontaneously resolving autoimmune disease m ay have implications for the understanding of the mechanism by which a n autoimmune attack is terminated and for the design of therapeutic st rategies to facilitate this process.