Experimental allergic encephalomyelitis in rhesus monkeys: II. Treatment of EAE with anti-T lymphocyte subset monoclonal antibodies.

Experimental allergic encephalomyelitis was induced in rhesus monkeys by immunization with bovine brain homogenate emulsified in complete Freund's adjuvant. Four monkeys were treated with anti-CD4 (OKT4+4A) monoclonal antibodies after the onset of clinical signs. One monkey developed a chronic-progressive course of EAE and was killed after a significantly prolonged disease of 19 days. One monkey had a relapse and survived with stable neurological signs. Two monkeys fully recovered. OKT4+4A treatment resulted in a short-term clearance of CD4+ lymphocytes and a reduction in granulocytes. Granulocytes may be attracted to the brain by chemotactic factors produced by CD4+ lymphocytes and are responsible for the development of the lethal granulocytic lesions. Clearance of CD4+ lymphocytes successfully prevented granulocytes from migrating to the brain. Nuclear magnetic resonance imaging showed extensive lesions during an acute attack, but these lesions became undetectable when the monkeys recovered. These results indicate that treatment with OKT4+4A can successfully reverse clinical signs of EAE. Four untreated monkeys and one monkey treated with OKT8F died of acute EAE within 3 days of the onset of clinical signs.