Glia cells as immunoregulatory elements. Up- and down-regulatory activities of astrocyte clones

TGF-beta1-dependent differential expression of a rat homolog for latent TGF-beta binding protein in astrocytes and C6 glioma cells

Transforming growth factor-beta1 (TGF-beta1) is widely recognized for its multiple roles in development, cellular maintenance, and protection against injury. In the brain, TGF-beta1 upregulation in microglia/macrophages is a predominant response to lesion and during pathology. However, the precise functions of TGF-beta1 in this context are still enigmatic. The present study investigates changes in astroglial gene expression as a major target of TGF-beta1 signaling in the brain. Differential display reverse transcription-polymerase chain reaction (DDRT-PCR) was used to identify several gene fragments differentially regulated by TGF-beta1 in rat astrocytes and C6 glioma cells. Among the cDNAs regulated by TGF-beta1 in C6 cells two cDNAs showed homology to alpha-tropomyosin and glycerol-3-phosphate dehydrogenase, respectively. Cloning of a full length cDNA corresponding to a differentially regulated gene fragment revealed close homology to latent TGF-beta binding protein (LTBP)-2. Data using antisense LTBP-2 oligonucleotides to decrease LTBP-2 expression suggest that LTBP-2 functions to activate TGF-beta. Therefore, it is likely that upregulation of the rat LTBP-2 homolog mRNA in C6 cells and cortical astrocytes by TGF-1 might lead to self-activation and exaggeration of TGF-beta signaling. These data will extend our current understanding of TGF-beta1 functioning on lesion-related features of glial cells.

Quantitative assessment of myelin basic protein-reactive T cell entry to the central nervous system by using oligonucleotide probes complementary to VDJ junctional sequences of rat TCR beta-chain

The VDJ junctional region represents the most diverse part of the antigenic TCR. We have previously reported that of 200 sequenced TCR beta-chains of rat MBP-reactive T cells, rarely did two share sequence homology over the entire CDR3 region. In this study, we demonstrate that sequences of the TCR CDR3 region are excellent clonotypic markers for rat MBP-reactive T cell clones and oligonucleotide probes complementary to the CDR3 region of three T cell clones specifically recognized the TCR from which they were derived, but failed to recognize syngeneic T cells that express a similar TCR beta-chain or T cells that share both V beta and J beta usage. To explore this observation, we determined the ability of MBP-reactive T cell clones to enter the CNS. We were able to show that some MBP-reactive T cell clones have an augmented ability to enter the CNS and that fully-activated T cells have a higher penetrating activity than their less-activated T cell counterparts.

Characterization of brain-isolated rat encephalitogenic T cell lines

In the present study, we have isolated and characterized five myelin basic protein (MBP)-reactive T cell lines directly from the brains of Lewis rats during the early paralytic phase of experimental autoimmune encephalomyelitis (EAE). Each T cell line responded to the dominant encephalitogenic epitope spanning residues 68-88, and did not react against the conserved encephalitogenic epitope [MBP(87-99)] or the nonencephalitogenic MBP epitope [MBP(50-69)]. We determined the T cell receptor (TcR) beta chain usage by polymerase chain reaction, DNA sequencing analysis and by generation of MBP-reactive hybridomas from one of the T cell lines (BT74). The results revealed that brain-infiltrating, MBP-reactive T cells freshly isolated early in the course of the disease exhibit TcR diversity.