GAMMA-DELTA T-CELL RECEPTOR REPERTOIRE IN BRAIN-LESIONS OF PATIENTS WITH MULTIPLE-SCLEROSIS

The identification of activated T cells in the brains of patients with multiple sclerosis (MS) suggests that these cells are critical in the pathogenesis of this disease. Recently we have used the PCR method to analyse rearrangements of Valpha and Vbeta genes of the T cell receptor (TCR) in samples of MS and control brains. The results of these studies showed that TCR V gene usage in MS brains may be restricted and in particular that Vbeta genes may be preferentially rearranged in certain HLA haplotypes associated with susceptibility to MS. In view of the recent evidence that T lymphocytes bearing the gammadelta chains may have autoreactive potential, we have assessed whether or not such TCR-bearing lymphocytes were also present in chronic MS lesions. TCR Vgamma and Vdelta were analysed by the PCR method using a panel of Vgamma and Vdelta primers paired with Cgamma or Cdelta primers in 12 MS brains, as well as in brain samples of ten normal post-mortem cases and three neurological controls. TCR Vgamma-Cgamma and Vdelta-Cdelta rearrangements were confirmed using Southern blotting and hybridisation of the PCR products with specific Cgamma and Cdelta probes. Only one to four rearranged TCR Vgamma and Vdelta transcripts were detected in each of the 23 brain samples obtained from 12 MS patients, with the majority of gammadelta T cells expressing the Vgamma2 and Vdelta2 chains. In marked contrast, Vgamma and Vdelta transcripts could only be found in one of the ten non-neurological control brains analysed. To assess the clonality of Vgamma2 and Vdelta2 T cell receptor chains in the brain samples of MS patients, we have sequenced the junctional regions of the TCR Vgamma-N-Jgamma-Cgamma and Vdelta-N-Ddelta-N-Jdelta-Cdelta segments amplified from brain tissues, CSF and spleens of two MS patients and from the spleen of two control subjects. The sequence analysis obtained so far shows no compelling evidence of an MS specific expansion of one or more clones expressing particular types of gammadelta T cell receptors. In contrast, a clonal expansion of a different population of TCR gammadelta-bearing T cells was found in the spleen of both an MS patient and one of the control individuals. These results suggests that the gammadelta T cell response at the site of chronic lesions, involve a number of clones, possibly in response to several inflammatory antigenic stimuli. Whether or not gammadelta T cells are involved in the initiation of MS or in the chronicity of the disease remains to be elucidated.