The expression of mouse T-cell receptor TCRDV genes in BALB/c spleen

Visualization and quantification of monoallelic TCRα gene rearrangement in αβ T cells

T-cell receptor α (TCRα) chain rearrangement is not constrained by allelic exclusion and thus αβ T cells frequently have rearranged both alleles of this locus. Thereby, stepwise secondary rearrangements of both TCRα loci further increase the odds for generation of an α-chain that can be positively selected in combination with a pre-existing TCRβ chain. Previous studies estimated that approximately 2-12% of murine and human αβ T cells still carry one TCRα locus in germline configuration, which must comprise a partially or even fully rearranged TCRδ locus. However, these estimates are based on a relatively small amount of individual αβ T-cell clones and αβ T-cell hybridomas analyzed to date. To address this issue more accurately, we made use of a mouse model, in which a fluorescent reporter protein is introduced into the constant region of the TCRδ locus. In this TcrdH2BeGFP system, fluorescence emanating from retained TCRδ loci enabled us to quantify monoallelically rearranged αβ T cells on a single-cell basis. Via fluorescence-activated cell sorting analysis, we determined the frequency of monoallelic TCRα rearrangements to be 1.7% in both peripheral CD4(+) and CD8(+) αβ T cells. Furthermore, we found a skewed 5' Jα gene utilization of the rearranged TCRα allele in T cells with monoallelic TCRα rearrangements. This is in line with previous descriptions of a tight interallelic positional coincidence of Jα gene segments used on both TCRα alleles. Finally, analysis of T cells from transgenic mice harboring only one functional TCRα locus implied the existence of very rare unusual translocation or episomal reintegration events of formerly excised TCRδ loci.

Distribution and development of the postnatal murine Vδ1 T-cell receptor repertoire

Murine γ/δ T cells express canonical Vγ5Vδ1 chains in the epidermis and Vγ6Vδ1 chains at reproductive sites. Both subsets carry an identical Vδ1-Dδ2-Jδ2 chain which completely lacks junctional diversity. These cells are thought to monitor tissue integrity via recognition of stress-induced self antigens. In this study, we showed by reverse transcription-polymerase chain reaction (RT-PCR), complementarity determining region 3 (CDR3) spectratyping and sequencing of the junctional regions of Vδ1 chains from C57BL/6 mice (aged 1 day to 14 months) that the canonical Vδ1-Dδ2-Jδ2 chain is also consistently present at other sites such as the thymus, gut, lung, liver, spleen and peripheral blood. In addition, we found multiple Vδ1 chains with fetal type rearrangements which were also shared among organs and among animals. These Vδ1 chains were typically characterized by a conserved amino acid motif, 'GGIRA'. Furthermore, by analysing the early postnatal period at days 10 and 16, we demonstrated that the diversification of the thymic Vδ1 repertoire is not paralleled by a diversification of extrathymic Vδ1+γ/δ T cells. This indicates that only fetal type rearrangements survive at extrathymic sites. In conclusion, γ/δ T cells expressing the canonical Vδ1-Dδ2-Jδ2 chain are not unique to the skin and reproductive sites. Furthermore, we found other γ/δ T cells expressing fetal type Vδ1 chains which were shared among different organs and animals. Thus, γ/δ T cells expressing conserved Vδ1 chains are likely to have important functions. We suggest a model in which this subset continuously recirculates throughout the organism and rapidly responds to stress-induced self antigens.

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.

Expression of the T cell receptor delta-chain repertoire in mouse lymph node

Despite the potential for extensive diversity of gamma delta TCR, especially for delta-chains, expression of the gamma delta TCR repertoire in various mouse epithelial tissues is highly restricted. This implies that the recognition of antigen by gamma delta T cells may also be limited. To date, however, few studies have examined gamma delta TCR diversity in peripheral lymphoid tissue. This report presents the V delta usage and junctional region sequences of TCR delta-chain transcripts derived from the lymph nodes of normal (PL/J x SJ/L) F1 mice. Rearranged TCR V delta-C delta transcripts were amplified by PCR for TCR delta-chain cDNA using oligonucleotide primers specific for the murine V delta 1 to V delta 7 genes and the C delta region. Following cloning of the polymerase chain reaction-amplified TCR delta cDNA, the extent of junctional diversity was assessed by nucleotide sequencing of the V-D-J junctions of individual TCR cDNA clones. With the exception of V delta 3, all V delta genes were expressed in mouse lymph node. Furthermore, predominant usage of J delta 1 was found in cDNA clones expressing V delta 2, V delta 4, V delta 5, V delta 6 and V delta 7 gene segments but despite this there was extensive junctional diversity of delta-chains primarily due to the usage of multiple D delta segments and N-nucleotide sequence addition. In contrast, the V delta 1 cDNA clones had limited heterogeneity consisting mostly of V delta 1 directly spliced to C delta gene rearrangements. These results show that the expressed murine peripheral TCR delta-chain repertoire is extremely diverse indicating that gamma delta T cells may potentially recognize a large number of antigens, and play an important role in contributing to host immune responses.