Disparate types of gamma delta T cell

Pulmonary V gamma 4+ gamma delta T cells have proinflammatory and antiviral effects in viral lung disease

Host defenses, while effecting viral clearance, contribute substantially to inflammation and disease. This double action is a substantial obstacle to the development of safe and effective vaccines against many agents, particularly respiratory syncytial virus (RSV). RSV is a common cold virus and the major cause of infantile bronchiolitis worldwide. The role of alphabeta T cells in RSV-driven immunopathology is well studied, but little is known about the role of "unconventional" T cells. During primary RSV challenge of BALB/c mice, some Vgamma7+ gammadelta T cells were present; however, immunization with a live vaccinia vector expressing RSV F protein substantially enhanced Vgamma4+ gammadelta T cell influx after RSV infection. Harvested early, these cells produced IFN-gamma, TNF, and RANTES after ex vivo stimulation. By contrast, those recruited 5 days after challenge made IL-4, IL-5, and IL-10. Depletion of gammadelta T cells in vivo reduced lung inflammation and disease severity and slightly increased peak viral replication but did not prevent viral clearance. These studies demonstrate a novel role for gammadelta T cells in the development of immunopathology and cellular influx into the lungs after immunization and RSV challenge. Though a minor population, gammadelta T cells have a critical influence on disease and are an attractive interventional target in the alleviation of viral lung disease.

On the role of the pre-T cell receptor in alphabeta versus gammadelta T lineage commitment

The role of the pre-T cell receptor (TCR) in lineage commitment to the gammadelta versus alphabeta lineage of T cells was addressed by analyzing TCRbeta chain rearrangements in gammadelta T cells from wild-type and pre-TCR-deficient mice by single cell polymerase chain reaction. Results show that the pre-TCR selects against gammadelta T cells containing rearranged Vbeta genes and that gammadelta T cell precursors but not gammadelta T cells express the pre-TCRalpha protein. Furthermore, pre-TCR-induced proliferation could not be detected in gammadelta T cells. We propose that the pre-TCR commits developing T cells to the alphabeta lineage by an instructive mechanism that has largely replaced an evolutionary more ancient stochastic mechanism of lineage commitment.

Disruption of epithelial gamma delta T cell repertoires by mutation of the Syk tyrosine kinase

Chimeric mice in which lymphocytes are deficient in the Syk tyrosine kinase have been created. Compared with Syk-positive controls, mice with Syk -/- lymphocytes display substantial depletion of intraepithelial gamma delta T cells in the skin and gut, with developmental arrest occurring after antigen receptor gene rearrangement. In this dependence on Syk, subsets of intraepithelial gamma delta T cells are similar to B cells, but distinct from splenic gamma delta T cells that develop and expand in Syk-deficient mice. The characteristic associations of certain T-cell receptor V gamma/V delta gene rearrangements with specific epithelia are also disrupted by Syk deficiency.

Ontogenic development and tissue distribution of V gamma 1-expressing gamma/delta T lymphocytes in normal mice

A hamster monoclonal antibody (mAb) recognizing an epitope in the V gamma 1-J gamma 4-C gamma 4 chain of the gamma/delta T cell receptor has been generated. Using this mAb, we have quantitated the occurrence of V gamma 1-bearing gamma/delta T cells in the developing thymus and in the lymphoid organs and several epithelia of adult mice. The V gamma 1-expressing cells constitute a minor gamma/delta T cell subpopulation during fetal and early postnatal life, but they constitute a major population of gamma/delta T cells in the thymus and in the peripheral lymphoid organs in adult mice. In addition, we found that V gamma 1-bearing cells comprise a large proportion (15-60%) of the gamma/delta T cells present in the intestinal epithelium (i-IEL) in all strains of mice tested. V gamma 1+ i-IEL are present in athymic (nude) mice and in antigen-free mice, demonstrating that they can develop extrathymically and that their presence in the intestinal epithelium is independent of the antigenic load of the gut. Our results show that V gamma 1-bearing lymphocytes account for the largest population of gamma/delta T cells in the mouse. This population includes a thymus-dependent component that homes to the secondary lymphoid organs and a thymus-independent component that constitutes a major fraction of the gamma/delta i-IELs.

Dynamic response of murine gut intraepithelial T cells after infection by the coccidian parasite Eimeria

The response of murine intraepithelial lymphocyte (IEL) populations to challenge by Eimeria vermiformis, a naturally occurring protozoan parasite of the gut epithelium, has been studied. The number of recoverable IEL increased within 3 days post infection, was depleted by day 7 post infection, but was significantly increased again by about day 14 post infection. Special attention was paid to gamma delta+ IEL T cells, because they are of unknown functions. These cells showed changes in numbers similar to the total IEL population. Moreover, by day 3, increased expression was detected among gamma delta+ IEL T cells, of T cell receptor genes not constitutively associated with the intestine. These results demonstrate that the IEL repertoire, and within that, the gamma delta+ T cell repertoire, can be extremely dynamic post infection with a naturally occurring epithelial-tropic pathogen. In considering the potential benefits of such IEL changes, we hypothesize that they may be relevant to the transient protection of the host's epithelium, both from parasitic re-infection, and from potentially damaging inflammation.

New T-cell receptor gamma haplotypes in wild mice and evidence for limited Tcrg-V gene polymorphism

Tcrg gene polymorphism was investigated by Southern blot analysis on a panel of laboratory and wild mouse strains using a set of probes which identify all known Tcrg-V and -C genes. Only three haplotypes are found in laboratory mice: gA, gB, and gC which are represented by BALB/c, AKR, and DBA/2 prototypes respectively. gA and gC haplotypes are the most frequent among laboratory mice whereas gB is poorly represented. Seven new haplotypes are described among 23 wild mice corresponding to four Mus musculus subspecies (Mus mus domesticus, castaneus, musculus, and molossinus). However, only a few new alleles of individual genes are observed. Tcrg-V genes located at the 5' end of the Tcrg locus (V7 and V4) appear to be nonpolymorphic whereas two Tcrg-V3, -V5, -V6, -C4 and three Tcrg-V1, -V2, -C1, -C2, and -C3 specific restriction fragment length polymorphisms are detected. These results indicate a relatively high degree of conservation of Tcrg genes as compared to other members of the immunoglogulin (Ig) gene family and might be related to the specifity and function of gamma delta T cells. Several of the new haplotypes described here result from point mutations in noncoding Tcrg-V or -C gene-flanking regions. Recombinations may have also participated in the evolution of the Tcrg locus. Finally, these new Tcrg haplotypes are unequally distributed among the four M. m. subspecies and support the idea that the gA and gC haplotypes found in laboratory mice are inherited from M. m. domesticus whereas gB might originate from asian subspecies (castaneus, musculus or molossinus).