Experimental allergic encephalomyelitis in rhesus monkeys: I. Immunological parameters in EAE resistant and susceptible rhesus monkeys.

Immunological parameters in rhesus monkeys, resistant and susceptible to experimental allergic encephalomyelitis (EAE), were studied. Monkeys immunized with complete Freund's adjuvant (CFA) alone and EAE resistant monkeys immunized with a low dose of bovine brain homogenate emulsified in CFA did not show significant fluctuations in numbers of granulocytes, lymphocytes and lymphocyte subsets (CD4; CD8; GM13, a subset of CD8) and anti-brain homogenate antibody titres remained low. EAE susceptible monkeys immunized with a high dose of myelin developed EAE significantly faster than monkeys immunized with a low dose of brain homogenate. During the induction phase all EAE susceptible monkeys, in contrast to the CFA controls and EAE resistant monkeys, showed an increase in the numbers of granulocytes and the CD4/CD8 ratios and had high antibody titres specific for the immunizing antigens. The most significant disease-related changes were observed after the onset of clinical signs. These included a granulocytosis, a lymphopenia and a decrease in the CD4/CD8 ratio, indicating a selective loss of CD4+ lymphocytes. A major difference between monkeys immunized with myelin and brain homogenate was the significant increase in the percentage of GM13+ lymphocytes after the onset of clinical signs in the latter group. Increases in the CD4/CD8 ratio and antibody titres during the induction phase may be prognostic factors for the subsequent development of EAE.