Mononuclear cell accumulation and plasma protein extravasation (PPE) during induction, remission and re-challenge of experimental allergic encephalomyelitis in the rat

Abstract

Plasma protein extravasation (PPE) and cell accumulation have been studied in the CNS of rats during experimental allergic encephalomyelitis (EAE) using radio-isotopic techniques. Use of such techniques makes it possible to study objectively and conveniently the rate of cell infiltration and PPE during the disease process in relation to clinical signs and time after immunization. The following observations have been made: 1. (a) After the first immunization, the number of rats showing increased PPE in the CNS correlated well with the severity of EAE. 2. (b) Mononuclear cell infiltration into brain and spinal cord during EAE did not parallel one another; infiltration being of earlier onset and shorter duration in the spinal cord, in comparison with brain. 3. (c) Animals re-challenged with encephalitogenic antigen showed considerably increased cellular infiltration into the brain but failed to exhibit comparable infiltration in the spinal cord. In this case infiltration of cells is not accompanied by increased PPE, in contrast to what is seen during primary disease. Increased infiltration into the brain of re-challenged animals appears, therefore, unrelated to gross damage of vascular endothelium. 4. (d) The present results show that cell accumulation and PPE may be dissociated due to different rates of accumulation and disappearance.