Passive transfer of allergic encephalomyelitis in rats: a tool for drug mechanism studies and detecting late-acting immunosuppressants

A strategy is described for evaluating drugs against different phases in the development of an auto allergic disease, experimental allergic encephalomyelitis. It is based on a cell transfer technique whereby the disease is passively transferred with lymphoid cells from actively immunized donor rats to normal syngeneic rats = passive recipients. Drugs may be applied in vivo to either the cell donors or the cell recipients or to cells in vitro whilst in transit; their efficiency being determined by the severity of the passive disease (weight loss, paralysis) in the recipients. Examples are given illustrating the application of these techniques to: evaluating the lymphocyte-deactivating activity of various nitrogen mustards in vitro; recognizing drugs, e.g. gold derivatives, clofazimine, etc. that are not conventional immunosuppressant (or cytostatic) agents which, when given to the recipient animals, may prevent the expression of the adopted disease; comparing some known immunosuppressants for potency, duration of action, etc.; demonstrating the versatility of cycloleucine, ICI-47,776, etc. Some merits of the strategy are discussed vis a vis using the local graft-versus-host reaction in rats to search for new drugs.