T cells in multiple sclerosis and inflammatory central nervous system diseases.

Using murine monoclonal antibodies to mark total T cells, we have found rapid migration of T cells into the CSF in progressive multiple sclerosis patients, suggesting that the ongoing inflammatory responses in the CNS may depend on the continued movement of cells from the periphery into the target organ. Cloning experiments have indicated that the T cells present in the CSF during viral and post-viral encephalomyelitis represent sequestered populations of antigen-specific cells. In more chronic disease processes, these cells may also have restricted clonality as measured by the frequency of different T-cell receptor gene rearrangements on Southern blotting. It is known that there is restricted clonality of the B-cell immunoglobulin response in the CSF compartment with inflammatory CNS diseases, and with infections the majority of these so-called oligoclonal antibodies are directed against the exciting antigen and are synthesized in the CNS. Although we believe that T cells in the CNS originate from the blood, during the course of an inflammatory response the antigen and clonally-restricted populations found in the CSF may represent either selective migration or selective accumulation in the CNS. Selective migration might occur at the endothelial barrier as these cells can express Class II MHC antigens and act as antigen-presenting cells in the CNS (McCarron et al. 1985). Selective accumulation of T cells in the CNS might occur after non-specific migration of cells into the CNS followed by proliferation and expansion of T cells that have been induced by antigens in the brain. Antigen-presenting cells that are present in situ, such as astrocytes, may also play a role in the selective expansion of T cells in the CSF (Fontana et al. 1984). Alternatively, it is possible that T cells are induced to expand in the target CNS tissue non-specifically, e.g., via the CD2 pathway. In this regard, we have observed that CSF T cells exhibit alterations in stimulation by anti-T112 + anti-T113 monoclonal antibodies. The mechanism of damage to CNS tissue by immune cells is essentially unknown. For example there are no clear links between antibodies present in the CNS and CNS damage in SSPE where high titers of anti-measles antibodies are present. Whereas we did not observe high frequencies of measles-reactive cells in the CSF of a subject with SSPE, we did observe MHC non-restricted cytotoxic T cells which expressed TCR-gamma chains rather than alpha-beta chains.(ABSTRACT TRUNCATED AT 400 WORDS)