Identification of two distinct function gamma delta TCR complexes on the surface of a human T cell clone

Expression of TCR-Vβ peptides by murine bone marrow cells does not identify T-cell progenitors

Germline transcription has been described for both immunoglobulin and T-cell receptor (TCR) genes, raising questions of their functional significance during haematopoiesis. Previously, an immature murine T-cell line was shown to bind antibody to TCR-Vβ8.2 in absence of anti-Cβ antibody binding, and an equivalent cell subset was also identified in the mesenteric lymph node. Here, we investigate whether germline transcription and cell surface Vβ8.2 expression could therefore represent a potential marker of T-cell progenitors. Cells with the TCR phenotype of Vβ8.2⁺Cβ⁻ are found in several lymphoid sites, and among the lineage-negative (Lin⁻) fraction of hematopoietic progenitors in bone marrow (BM). Cell surface marker analysis of these cells identified subsets reflecting common lymphoid progenitors, common myeloid progenitors and multipotential progenitors. To assess whether the Lin⁻Vβ8.2⁺Cβ⁻ BM subset contains hematopoietic progenitors, cells were sorted and adoptively transferred into sub-lethally irradiated recipients. No T-cell or myeloid progeny were detected following introduction of cells via the intrathymic or intravenous routes. However, B-cell development was detected in spleen. This pattern of restricted in vivo reconstitution disputes Lin⁻Vβ8.2⁺Cβ⁻ BM cells as committed T-cell progenitors, but raises the possibility of progenitors with potential for B-cell development.

Expression of T-cell receptor genes during early T-cell development

Lymphoid cell development is an ordered process that begins in the embryo in specific sites and progresses through multiple differentiative steps to production of T- and B-cells. Lymphoid cell production is marked by the rearrangement process, which gives rise to mature cells expressing antigen-specific T-cell receptors (TCR) and immunoglobulins (Ig). While most transcripts arising from TCR or Ig loci reflect fully rearranged genes, germline transcripts have been identified, but these have always been thought to have no specific purpose. Germline transcription from either unrearranged TCR or unrearranged Ig loci was commonly associated with an open chromatin configuration during VDJ recombination. Since only early T and B cells undergo rearrangement, the association of germline transcription with the rearrangement process has served as an appropriate explanation for expression of these transcripts in early T- and B-cell progenitors. However, germline TCR-V beta 8.2 transcripts have now been identified in cells from RAG(-/-) mice, in the absence of the VDJ rearrangement event and recombinase activity. Recent data now suggest that germline TCR-V beta transcription is a developmentally regulated lymphoid cell phenomenon. Germline transcripts could also encode a protein that plays a functional role during lymphoid cell development. In the least, germline transcripts serve as markers of early lymphoid progenitors.

Study of Herpesvirus saimiri immortalization of gammadelta T cells derived from peripheral blood and CSF of multiple sclerosis patients

Human gammadelta T cells are an integral part of the innate immune system and have been difficult to study owing primarily to their relatively low abundance and their fastidious culture properties associated with short in vitro lifespan. Their increased presence within multiple sclerosis (MS) white matter plaques compared to peripheral blood (PB) suggests a specific interaction with central nervous system (CNS) tissues. This fact, together with their innate ability to lyse human oligodendrocytes in culture implicate them possibly in the pathogenesis of MS. To further investigate their potential role in MS, we studied whether gammadelta T cells could be effectively immortalized using Herpesvirus saimiri (HVS), so that they could be studied in longer-term cultures. Effective culture conditions were established resulting in efficient HVS growth transformation of multiple PB and CSF gammadelta T cell lines and clones that could exist in IL-2-dependent culture for periods in excess of 2 years. Phenotypic and functional comparison studies with parental nontransformed gammadelta T cells were performed to characterize the changes that possibly induced by viral transformation. Using panels of transformed gammadelta T cell clones representing discrete gammadelta TcR subtypes, there was no apparent correlation between intracytoplasmic cytokine expression or tumor cell cytotoxicity with a specific TcR. All transformed gammadelta T cells analyzed, regardless of their compartment of origin, strongly expressed intracytoplasmic IFN-gamma and TNF-alpha, but little IL-2 or anti-inflammatory IL-4 or IL-10. These results indicate that HVS transformation of gammadelta T cells can be used to generate lines and clones from both the CSF and PB compartments for further study and elucidation of their potential role in MS pathogenesis.