Evidence for gamma delta T cells with a restricted V delta 6 junctional region in the normal mouse central nervous system

In this study we present evidence that gamma delta T cells are present in t he normal mouse central nervous system (CNS). Compared with matching spleen gamma delta T cells, CNS gamma delta T cells expressed only the CD45RB(low ) phenotype, suggesting that CNS gamma delta T cells belong to the memory c ell population. Approximately 20% expressed exclusively the CD8 alpha beta heterodimer, consistent with a thymic origin, gamma delta T cells in both s pleen and CNS expressed higher levels of the IL-2r beta (CD122), as well as Fas and FasL, than T cells, suggesting that these cells function as immuno regulatory T cells. RT-PCR analysis showed almost exclusive use of V delta 6 in the CNS whereas more V delta genes were expressed in the spleen. Seque ncing of V delta 6 RT-PCR products demonstrated a polyclonal population of T cells in the spleen but a more clonal population within the CNS. The pred ominant 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 c irculating gamma delta T cells traffics through the CNS. Thus all major pop ulations of lymphocytes can be detected in the normal CNS and as such may p lay specific roles in the immunological surveillance of that organ. (C) 199 9 Published by Elsevier Science B.V. All rights reserved.