APOPTOSIS OF V-BETA-8.2(-LYMPHOCYTES IN THE SPINAL-CORD DURING RECOVERY FROM EXPERIMENTAL AUTOIMMUNE ENCEPHALOMYELITIS INDUCED IN LEWIS RATS BY INOCULATION WITH MYELIN BASIC-PROTEIN() T)

To study T cell apoptosis during spontaneous recovery from experimenta l autoimmune encephalomyelitis (EAE), we extracted lymphocytes from th e spinal cords of Lewis rats with EAE induced by inoculation with myel in basic protein (MBP) and adjuvants. Using flow cytometry we assessed the numbers of CD5(+) and TCR alpha beta(+) lymphocytes, as well as V beta 8.2(+) lymphocytes, which constitute the predominant encephalito genic MBP-reactive cells in Lewis rats. Rats developed neurological si gns of disease 10-12 days after inoculation. The peak of disease was o n day 14 after inoculation and was followed by clinical recovery. The numbers of CD5(+) TCR alpha beta(+) and V beta 8.2+ cells obtained fro m the spinal cord were greatest on day 13. During spontaneous clinical recovery, there was a decline in the numbers of all the cells studied , with a selective loss of V beta 8.2(+) cells from the CD5(+) and TCR alpha beta(+) populations. To determine whether the decline in lympho cyte numbers was due to apoptosis, we used simultaneous surface labell ing and propidium iodide staining of the DNA of the cells extracted fr om the spinal cord. From day 14 onwards, there was selective enrichmen t of V beta 8.2(+) cells in the apoptotic population, and the percenta ge of V beta 8.2(+) cells undergoing apoptosis was greater than the pe rcentages of CD5(+) and TCR alpha beta(+) cells undergoing apoptosis. These findings indicate that recovery from acute EAE is associated wit h the selective apoptosis, in the central nervous system, of these dis ease-relevant cells. The findings in this study of actively induced EA E are similar to those of our previous study of EAE induced by transfe r of encephalitogenic MBP-specific T cells (Z. Tabi et al., fur. J. Im munol. 24: 2609-2617, 1994) and further support the hypothesis that se lective apoptosis of autoreactive T cells in the central nervous syste m is of primary importance in spontaneous recovery from EAE.