Apoptosis of T lymphocytes in experimental autoimmune encephalomyelitis. Evidence for programmed cell death as a mechanism to control inflammation in the brain.

In experimental autoimmune encephalomyelitis (EAE) myelin-specific T lymphocytes attack the myelinated tissue of the central nervous system (CNS). In the Lewis rat, EAE as a rule has an acute, monophasic course. With spontaneous clinical recovery the inflammatory CNS infiltrates are cleared from the nervous tissue within a few days. This is well in line with the remarkably low incidence of myelin-specific T cells present in EAE infiltrate. Combining immunocytochemical techniques, ultrastructural criteria and in situ nick translation we found up to 49% of T lymphocytes in EAE lesions showing signs of apoptosis at the time of recovery from disease. Our results suggest that apoptosis of T lymphocytes may be one possible mechanism to eliminate T lymphocytes from inflammatory brain lesions.