Evidence for gammadelta T cells with a restricted Vgamma6 junctional region in the normal mouse central nervous system.

In this study we present evidence that gammadelta T cells are present in the normal mouse central nervous system (CNS). Compared with matching spleen gammadelta T cells, CNS gammadelta T cells expressed only the CD45RBlow phenotype, suggesting that CNS gammadelta T cells belong to the memory cell population. Approximately 20% expressed exclusively the CD8alphabeta heterodimer, consistent with a thymic origin. Gammadelta T cells in both spleen and CNS expressed higher levels of the IL-2rbeta (CD122), as well as Fas and FasL, than alphabeta T cells, suggesting that these cells function as immunoregulatory T cells. RT-PCR analysis showed almost exclusive use of Vdelta6 in the CNS whereas more Vdelta genes were expressed in the spleen. Sequencing of Vdelta6 RT-PCR products demonstrated a polyclonal population of T cells in the spleen but a more clonal population within the CNS. The predominant CNS sequence was found in all animals studied and was also detected in the spleen. From these data we conclude that a selective component of circulating gammadelta T cells traffics through the CNS. Thus, all major populations of lymphocytes can be detected in the normal CNS and as such may play specific roles in the immunological surveillance of that organ.

Multiple sclerosis: the frequency of allelic forms of tumor necrosis factor and lymphotoxin-alpha.

The cytokines LTa and TNF have been implicated as major mediators of tissue injury in multiple sclerosis (MS). In this study we have assessed the frequency of specific polymorphisms for these genes in MS (n = 53) and controls (n = 81) using a highly sensitive, two stage nested polymerase chain reaction (PCR), with the second stage using mutation-specific primers. Genomic DNA was extracted from blood cells and the results confirmed by direct dideoxy chain termination sequencing. The frequency of the -308 G to A mutation in the TNF promoter region in normal controls was 15% and in MS was 24%. For LTa gene the exon 3 polymorphism allele A was detected in 36% of controls and 34% of the MS patients. In MS, the combined genotype TNF G + A and LTa C + C was present 6 times more frequently (12%) than in controls (2%), and patients with this genotype showed the highest EDSS scores. We found the TNF and LTa polymorphisms to occur independently from the HLA class II DR2 allele distribution in MS. Whilst the G - A polymorphism in TNF gene promoter has been studied previously in MS, with conflicting results, this is the first study that has addressed the exon 3 polymorphism in LTa in MS. The results indicate that this polymorphism is not linked with the higher genetic predisposition for MS, but that combined TNF G + A and LTa C + C genotype might contribute to development of the disease.

Multiple sclerosis: the increased frequency of the ICAM-1 exon 6 gene point mutation genetic type K469.

Intracellular adhesion molecule-1 (ICAM-1) plays an important role in the cascade of adhesion events in the homing of inflammatory cells to the central nervous system (CNS) in experimental autoimmune encephalomyelitis (EAE) and in multiple sclerosis (MS). Two single-base ICAM-1 polymorphisms have been described, in exons 4 and 6, changing codons 241 and 469 in the ICAM-1 gene, respectively. Both polymorphisms result in amino acid changes and can potentially lead to different interactions of ICAM-1 with its ligands. To detect ICAM-1 gene polymorphisms in MS, we have developed a highly sensitive and site-specific, two-stage, nested polymerase chain reaction. Genomic DNA was extracted from blood cells of 79 MS patients and 68 control subjects. The results were confirmed by direct dideoxy chain termination sequencing. The frequency of exon 6 allele T was found to be significantly higher in MS patients than in controls (68% vs 49%). Most interesting, the frequency of exon 6 homozygote K469 was significantly higher in MS patients than in controls (53% vs 34%). Higher frequency of the K469 genotype was found to be independent of possible linkage with the previously described MS susceptibility factor, the HLA class II DR2 allele. In the present study, we have shown for the first time the ICAM-1 gene polymorphisms in MS. The results indicate increased frequency of ICAM-1 exon 6 allele T in MS patients, which may contribute to the MS genetics background.