IDENTIFICATION OF CELL-TYPES PRODUCING RANTES, MIP-1-ALPHA AND MIP-1-BETA IN RAT EXPERIMENTAL AUTOIMMUNE ENCEPHALOMYELITIS BY IN-SITU HYBRIDIZATION

The chemokines RANTES, macrophage inflammatory protein (MIP)-1 alpha a nd MIP-1 beta are members of the beta-family of chemokines and potent chemoattractants for lymphocytes and monocytes. To investigate the fac tors which regulate lymphocyte traffic in experimental autoimmune ence phalomyelitis (EAE), we studied, by in situ hybridization analysis, th e kinetics of mRNA expression and the potent cellular sources of RANTE S, MIP-1 alpha and MIP-1 beta in the central nervous system (CNS) duri ng the course of EAE. RANTES-positive cells appeared in the subarachno id space and infiltrated the subpial region at around day 10, increase d to a peak at days 12-13 and then decreased following the resolution of the acute phase of EAE, though elevated RANTES message expressions still remained on chronic subclinical stage. Most of RANTES positive c ells were identified as T-lymphocytes located mainly around blood vess els, by combined studies of in situ hybridization and immunohistochemi stry. The remainder of the RANTES-positive cells were astrocytes and m acrophages/microglia. MIP-1 alpha and MIP-1 beta mRNA-positive cells a ppeared around day 10, increased further on days 12-13 and then gradua lly decreased. Most of the MIP-1 alpha- and MIP-1 beta-positive mononu clear cells were located around blood vessels. The kinetics of RANTES, MIP-1 alpha and MIP-1 beta expression paralleled those of the recruit ment of infiltrating inflammatory cells and disease severity. Our obse rvations support the possibility that chemokine production by T-cells, macrophages and astrocytes lead to the infiltration of inflammatory c ells into the CNS parenchyma during the acute phase of EAE.