Experimental allergic encephalomyelitis. Frequent sampling of blood alters disease course.

Previous studies have shown that Strain 13 guinea pigs sensitised for experimental allergic encephalomyelitis (EAE) as adults usually develop an acute, fatal form of disease while animals inoculated as juveniles usually display a chronic relapsing form. The present study reports that following repeated short-interval blood sampling by cardiac puncture for the estimation of lymphocyte populations, some adult Strain 13 guinea pigs sensitised for acute EAE unexpectedly survived and developed chronic EAE, while a group of juveniles sensitised for chronic EAE and bled under the same conditions, developed a more severe, acute form of EAE. It is suggested that this reversal of disease course was related to the depletion of circulating factors.