A tumor-suppressor function for Fas (CD95) revealed in T cell-deficient mice.

Fas (CD95) and its ligand are central regulatory molecules in hematopoietic cells. Previous studies have suggested a role for Fas in the regulation of tumor progression, but Fas has not yet been conclusively identified as a tumor suppressor. Fas-deficient individuals lack malignant tumors, perhaps because of regulation by T cells. To investigate such a possibility, mice deficient in both T cells and Fas were generated, and they were found to develop severe B cell dysregulation characterized by malignant, lethal B cell lymphoma. Lymphoma arose from a monoclonal B220+CD19-CD5-CD23- B cell secreting immunoglobulin M, kappa rheumatoid factor. In contrast, animals containing alpha beta T cells, gamma delta T cells, and/or functional Fas suppressed the development of lymphoma. These data indicate that Fas functions as a tumor suppressor, and identifies roles for both alpha beta T cells and gamma delta T cells in Fas-independent tumor regulation.

Late dominance of the inflammatory process in murine influenza by gamma/delta + T cells.

The inflammatory response in the lungs of mice infected with an influenza A virus consists largely of macrophages and CD3+ T cells. Most T lymphocytes recovered before day 7 after infection express mRNA for the T cell receptor alpha/beta (TCR-alpha/beta), while TCR-gamma/delta mRNA+ cells are found at much higher frequency over the next 7 d. The predominant surface phenotype for the TCR-gamma/delta mRNA+ population is CD3+4-8-TCR-alpha/beta-. Some lymphocytes expressing all the known V gamma genes are found in the inflammatory exudate, but V gamma 2+/V gamma 1+ and V gamma 4+ T cells are present at highest frequency. The response is staged, with maximal numbers of V gamma 4+ cells occurring on day 10 after infection, while the predominant phenotype on day 13 is V gamma 2/V gamma 1+. The emerging peak in numbers of V gamma 4+ lymphocytes is paralleled by increasing numbers of macrophages expressing hsp mRNA. The later maxima found for the V gamma 2+/V gamma 1+ T cells is consistent with the possibility that at least some of these lymphocytes are responding to the hsp+ cells and are functioning to resolve the inflammatory process.

Identification of a dominant epitope of glutamic acid decarboxylase (GAD-65) recognized by autoantibodies in stiff-man syndrome.

Glutamic acid decarboxylase (GAD) is the enzyme that synthesizes the neurotransmitter gamma-aminobutyric acid (GABA) in neurons and in pancreatic beta cells. It is a major target of autoimmunity in Stiff-Man syndrome (SMS), a rare neurological disease, and in insulin-dependent diabetes mellitus. The two GAD isoforms, GAD-65 and GAD-67, are the products of two different genes. GAD-67 and GAD-65 are very similar to each other in amino acid sequence and differ substantially only at their NH2-terminal region. We have investigated the reactivity of autoantibodies of 30 Stiff-Man syndrome patients to GAD. All patient sera contained antibodies that recognize strongly GAD-65, but also GAD-67, when tested by immunoprecipitation on brain extracts and by immunoprecipitation or immunocytochemistry on cells transfected with either the GAD-65 or the GAD-67 gene. When tested by Western blotting, all patient sera selectively recognized GAD-65. Western blot analysis of deletion mutants of GAD-65 demonstrated that autoantibodies are directed predominantly against two regions of the GAD-65 molecule. All SMS sera strongly recognized a fragment contained between amino acid 475 and the COOH terminus (amino acid 585). Within this region, amino acids 475-484 and 571-585 were required for reactivity. The requirement of these two discontinuous segments implies that the epitope is influenced by conformation. This reactivity is similar to that displayed by the monoclonal antibody GAD 6, suggesting the presence of a single immunodominant epitope (SMS-E1) in this region of GAD-65. In addition, most SMS sera recognized at least one epitope (SMS-E2) in the NH2-terminal domain of GAD-65 (amino acids 1-95). The demonstration in SMS patients of a strikingly homogeneous humoral autoimmune response against GAD and the identification of dominant autoreactive target regions may help to elucidate the molecular mechanisms of GAD processing and presentation involved in GAD autoimmunity. Moreover, the reactivity reported here of GAD autoantibodies in SMS partially differs from the reactivity of GAD autoantibodies in insulin-dependent diabetes mellitus, suggesting a link between the pattern of humoral autoimmunity and the clinical condition.

T cells with gamma/delta T cell receptors (TCR) of intestinal type are preferentially expanded in TCR-alpha-deficient lpr mice.

Fas-mediated apoptosis is essential for activation-induced cell death of alpha/beta T cells, but it is not clear what role, if any, it plays in regulating other components of the immune system. To study the role of Fas in gamma/delta T cell development, Fas-deficient lpr mice were bred with T cell receptor alpha gene-ablated (TCR-alpha-/-) mice to generate mice deficient in one or both genes. The TCR-alpha-/-, lpr/lpr mice had a nearly 10-fold increase in total lymph node cell (LNC) number compared with Fas-intact TCR-alpha-/- mice, because of expansion of TCR-gamma/delta+ and TCR-beta+ cells. In Fas-intact TCR-alpha-/- mice, approximately one third of the LNCs expressed TCR-gamma/delta. These were evenly divided between the CD4-, CD8-alpha+ and the CD4-, CD8- subsets, and rarely expressed the B220 epitope of CD45. In contrast, in TCR-alpha-/-, lpr/lpr mice, TCR-gamma/delta+ cells comprised half of the LNCs and were primarily CD4-, CD8-, and B220+. Moreover, Fas deficiency in TCR-alpha-/- mice caused a preferential expansion of gamma/delta T cells expressing variable region genes characteristic of intestinal intraepithelial lymphocytes. These results demonstrate a role for Fas in regulating the gamma/delta T cell contribution to peripheral lymph nodes. This mechanism may be most important in limiting the access of activated intestinal intraepithelial lymphocytes to the peripheral lymphoid system.

Gamma delta T cells from tolerized alpha beta T cell receptor (TCR)-deficient mice inhibit contact sensitivity-effector T cells in vivo, and their interferon-gamma production in vitro.

Contact sensitivity (CS) responses to reactive hapten Ag, such as picryl chloride (PCl) or oxazolone (OX), are classical examples of T cell-mediated immune responses in vivo that are clearly subject to multifaceted regulation. There is abundant evidence that downregulation of CS may be mediated by T cells exposed to high doses of Ag. This is termed high dose Ag tolerance. To clarify the T cell types that effect CS responses and mediate their downregulation, we have undertaken studies of CS in mice congenitally deficient in specific subsets of lymphocytes. The first such studies, using alpha beta T cell-deficient (TCR alpha -/-) mice, are presented here. The results clearly show that TCR alpha -/- mice cannot mount CS, implicating alpha beta T cells as the critical CS-effector cells. However, TCR alpha -/- mice can, after high dose tolerance, downregulate alpha +/+ CS-effector T cells adoptively transferred into them. By mixing ex vivo and then adoptive cell transfers in vivo, the active downregulatory cells in tolerized alpha -/- mice are shown to include gamma delta TCR+ cells that also can downregulate interferon-gamma production by the targeted CS-effector cells in vitro. Downregulation by gamma delta cells showed specificity for hapten, but was not restricted by the MHC. Together, these findings establish that gamma delta T cells cannot fulfill CS-effector functions performed by alpha beta T cells, but may fulfill an Ag-specific downregulatory role that may be directly comparable to reports of Ag-specific downregulation of IgE antibody responses by gamma delta T cells. Comparisons are likewise considered with downregulation by gamma delta T cells occurring in immune responses to pathogens, tumors, and allografts, and in systemic autoimmunity.

The biological activity of natural and mutant pTalpha alleles.

beta selection is a major checkpoint in early thymocyte differentiation, mediated by successful expression of the pre-T cell receptor (TCR) comprising the TCRbeta chain, CD3 proteins, and a surrogate TCRalpha chain, pTalpha. The mechanism of action of the pre-TCR is unresolved. In humans and mice, the pTalpha gene encodes two RNAs, pTalpha(a), and a substantially truncated form, pTalpha(b). This study shows that both are biologically active in their capacity to rescue multiple thymocyte defects in pTalpha(-/-) mice. Further active alleles of pTalpha include one that lacks both the major ectodomain and much of the long cytoplasmic tail (which is unique among antigen receptor chains), and another in which the cytoplasmic tail is substituted with the short tail of TCR Calpha. Thus, very little of the pTalpha chain is required for function. These data support a hypothesis that the primary role of pTalpha is to stabilize the pre-TCR, and that much of the conserved structure of pTalpha probably plays a critical regulatory role.

Germinal center formation, immunoglobulin class switching, and autoantibody production driven by "non alpha/beta" T cells.

The production of class-switched antibodies, particularly immunoglobulin (Ig) G1 and IgE, occurs efficiently in T cell receptor (TCR) alpha-/- mice that are congenitally devoid of alpha/beta T cells. This finding runs counter to a wealth of data indicating that IgG1 and IgE synthesis are largely dependent on the collaboration between B and alpha/beta T cells. Furthermore, many of the antibodies synthesized in TCR alpha-/- mice are reactive to a similar spectrum of self-antigens as that targeted by autoantibodies characterizing human systemic lupus erythematosus (SLE). SLE, too, is most commonly regarded as an alpha/beta T cell-mediated condition. To distinguish whether the development of autoantibodies in TCR alpha-/- mice is due to an intrinsic de-regulation of B cells, or to a heretofore poorly characterized collaboration between B and "non-alpha/beta T" cells, the phenotype has been reconstituted by transfer of various populations of B and non-alpha/beta T cells including cloned gamma/delta T cells derived from TCR alpha-/- mice, to severe combined immunodeficient (SCID) mice. The results establish that the reproducible production of IgG1 (including autoantibodies) is a product of non-alpha/beta T cell help that can be provided by gamma/delta T cells. This type of B-T collaboration sustains the production of germinal centers, lymphoid follicles that ordinarily are anatomical signatures of alpha/beta T-B cell collaboration. Thus, non-alpha/beta T cell help may drive Ig synthesis and autoreactivity under various circumstances, especially in cases of alpha/beta T cell immunodeficiency.

In vivo manipulation of Vgamma9Vdelta2 T cells with zoledronate and low-dose interleukin-2 for immunotherapy of advanced breast cancer patients.

The potent anti-tumour activities of gammadelta T cells have prompted the development of protocols in which gammadelta-agonists are administered to cancer patients. Encouraging results from small Phase I trials have fuelled efforts to characterize more clearly the application of this approach to unmet clinical needs such as metastatic carcinoma. To examine this approach in breast cancer, a Phase I trial was conducted in which zoledronate, a Vgamma9Vdelta2 T cell agonist, plus low-dose interleukin (IL)-2 were administered to 10 therapeutically terminal, advanced metastatic breast cancer patients. Treatment was well tolerated and promoted the effector maturation of Vgamma9Vdelta2 T cells in all patients. However, a statistically significant correlation of clinical outcome with peripheral Vgamma9Vdelta2 T cell numbers emerged, as seven patients who failed to sustain Vgamma9Vdelta2 T cells showed progressive clinical deterioration, while three patients who sustained robust peripheral Vgamma9Vdelta2 cell populations showed declining CA15-3 levels and displayed one instance of partial remission and two of stable disease, respectively. In the context of an earlier trial in prostate cancer, these data emphasize the strong linkage of Vgamma9Vdelta2 T cell status to reduced carcinoma progression, and suggest that zoledronate plus low-dose IL-2 offers a novel, safe and feasible approach to enhance this in a subset of treatment-refractory patients with advanced breast cancer.

γδ T cells compose a developmentally regulated intrauterine population and protect against vaginal candidiasis.

This most comprehensive analysis to date of γδ T cells in the murine uterus reveals them to compose a unique local T-cell compartment. Consistent with earlier reports, most cells expressed a canonical Vγ6Vδ1 TCR, and produced interleukin (IL)-17A upon stimulation. Nonetheless, contrasting with earlier reports, uterine γδ T cells were not obviously intraepithelial, being more akin to sub-epithelial Vγ6Vδ1+ T cells at several other anatomical sites. By contrast to other tissues however, the uterine compartment also included non-Vγ6+, IFN-γ-producing cells; was strikingly enriched in young mice; expressed genes hitherto associated with the uterus, including the progesterone receptor; and did not require microbes for development and/or maintenance. This notwithstanding, γδ T-cell deficiency severely impaired resistance to reproductive tract infection by Candida albicans, associated with decreased responses of IL-17-dependent neutrophils. These findings emphasise tissue-specific complexities of different mucosal γδ cell compartments, and their evident importance in lymphoid stress-surveillance against barrier infection.

Regression of melanoma metastases following treatment with the n-bisphosphonate zoledronate and localised radiotherapy.

We report a case of regression of pulmonary and bony metastases in a patient with malignant melanoma following palliative treatment with systemic zoledronate and localised radiotherapy to the bone. Zoledronate is a potent new bisphosphonate used for the treatment of metabolic bone diseases including bone metastases due to its inhibitory effect on osteoclasts. In the context of metastatic cancer zoledronate is routinely used to improve bone pain and reduce the frequency of skeletal events. There is also an increasing body of evidence suggesting that bisphosphonates exhibit anti-tumour properties. Bisphosphonates are able to activate Vgamma9Vdelta2 gamma-delta T cells which can be key players in the immune defence against malignant cells. Furthermore bisphosphonates have direct anti-proliferative, anti-metastatic and pro-apoptotic effects on tumour cells. These actions, together with their low side effect profile, may prove to be useful therapeutic tools in the treatment of cancer even in the absence of bone metastases. On the basis of this case report we here review the current literature on present preclinical and clinical studies using bisphosphonates for the treatment of cancer.

Normal expression of a rearranged and mutated c-myc oncogene after transfection into fibroblasts.

Expression of the c-myc oncogene is deregulated in a variety of malignancies. Rearrangement and mutation of the c-myc locus is a characteristic feature of human Burkitt's lymphoma. Whether deregulation is solely a result of mutation of c-myc or whether it is influenced by the transformed B cell context has not been determined. A translocated and mutated allele of c-myc was stably transfected into fibroblasts. The rearranged allele was expressed indistinguishably from a normal c-myc gene: it had serum-regulated expression, was transcribed with normal promoter preference, and was strongly attenuated. Thus mutations by themselves are insufficient to deregulate c-myc transcription.

The ins and outs of body surface immunology.

Rather than being confined to the secondary lymphoid tissue of the spleen and lymph nodes, large numbers of lymphocytes are intrinsically associated with the epithelial surfaces of the body. The best studied is gut-associated lymphoid tissue, but distinct epithelium-associated lymphoid tissue also exists in the reproductive tract, the lung, and the skin. The multiple cell types and functions composing these lymphoid tissues are increasingly seen as the key to how antigens delivered to body surfaces can elicit either immunogenic or tolerogenic responses. In some instances, these responses occur purely within the local body surface tissue, yet in other cases both local and systemic responses are elicited.

Conservation of T cell receptor conformation in epidermal gammadelta cells with disrupted primary Vgamma gene usage.

A feature that distinguishes gammadelta T cell subsets from most alphabeta T cells and B cells is the association of expression of single T cell receptor (TCR) gamma and delta variable (V) region gene segments with specific anatomic sites. Mice lacking the TCR Vgamma5 chain normally expressed by most dendritic epidermal T cells were shown to retain a conformational determinant (idiotype) ordinarily expressed exclusively by such Vgamma5+ cells. Conservation by shuffled gammadelta TCR chains of an idiotype associated with a specific anatomic site indicates that for TCRgammadelta, as for immunoglobulin, conformation is associated to a greater extent with the function or development of lymphocyte repertoires than is the use of particular gene segments.

Lymphoid development in mice congenitally lacking T cell receptor alpha beta-expressing cells.

Vertebrate T cells express either an alpha beta or gamma delta T cell receptor (TCR). The developmental relatedness of the two cell types is unresolved. alpha beta + T cells respond to specific pathogens by collaborating with immunoglobulin-producing B cells in distinct lymphoid organs such as the spleen and Peyer's patches. The precise influence of alpha beta + T cells on B cell development is poorly understood. To investigate the developmental effects of alpha beta + T cells on B cells and gamma delta + T cells, mice homozygous for a disrupted TCR alpha gene were generated. The homozygotes showed elimination of alpha beta + T cells and the loss of thymic medullae. Despite this, gamma delta + T cells developed in normal numbers, and there was an increase in splenic B cells.

Regulation of cutaneous malignancy by gammadelta T cells.

The localization of gammadelta T cells within epithelia suggests that these cells may contribute to the down-regulation of epithelial malignancies. We report that mice lacking gammadelta cells are highly susceptible to multiple regimens of cutaneous carcinogenesis. After exposure to carcinogens, skin cells expressed Rae-1 and H60, major histocompatibility complex-related molecules structurally resembling human MICA. Each of these is a ligand for NKG2d, a receptor expressed by cytolytic T cells and natural killer (NK) cells. In vitro, skin-associated NKG2d+ gammadelta cells killed skin carcinoma cells by a mechanism that was sensitive to blocking NKG2d engagement. Thus, local T cells may use evolutionarily conserved proteins to negatively regulate malignancy.

Establishing humanized mice using stem cells: maximizing the potential.

Studies on physiology and pathology as they relate to the immune system draw heavily upon rodent models. With the increasing impetus provided by initiatives in translational medicine, the demand for ever more sophisticated, 'humanized' murine models is greater than ever. However, the design and implementation of studies in such mice is far from trivial. Here we provide a technical perspective on the increasing interest in developing humanized mice. We give examples of primary data starting with the routine procurement of human donor material, through CD34(+) cell purification prior to engraftment to injection into immunocompromised mice. Our goal is to provide practical advice to the many investigators who may be commencing or considering such studies.

Immune responses to myelin proteins in Guillain-Barré syndrome.

BACKGROUND: Potential target autoantigens in the demyelinating form of Guillain-Barré syndrome (GBS) include the myelin proteins PMP22, P0 and P2. METHODS: We investigated immunoreactivity to P0, P2 and PMP22 proteins in 37 patients with GBS and 32 healthy controls. RESULTS: Antibodies to PMP22 or P0 peptides were detected at presentation in only 5 out of 37 patients. In ELISPOT assays, blood mononuclear cells from 15 out of 24 patients with GBS, but none of the control subjects, produced interleukin-10 (IL-10) in response to peptides from proteins P0, P2 or PMP22 (p = 0.0003). The cells from only two patients produced interferon-gamma (IFN gamma). The cells from 11 patients with GBS had increased IL-10 responses to peptides representing sequences from the extracellular domains of PMP22 before intravenous immunoglobulin (IVIg) treatment (p = 0.006). The cells from 11 patients with GBS, including 7 who responded to the extracellular domains of PMP22, had increased IL-10 responses to the intracellular domain of P0 before (p = 0.005) and those from 9 patients after they had been treated with IVIg (p = 0.01). CONCLUSIONS: Antibodies to P0 and PMP22 protein peptides do occur in GBS but are uncommon. Circulating mononuclear cell IFN gamma responses to P0, P2 and PMP22 myelin protein peptides are rare, but IL-10 responses occur significantly more often than in normal subjects. They might be part of a harmful pathogenetic process or represent a regulatory response.

Autoimmunity. Is antigen-specific suppression now unsuppressed?

Recent studies suggest that putative regulatory lymphocytes can effect antigen-specific down-regulation of autoimmunity. But we have yet to see how much this improves our picture of autoimmune disease progression.

Gamma(delta) T cells: non-classical ligands for non-classical cells.

A recent study describes direct binding between a gammadelta T-cell receptor and its ligand, T22, a non-classical class I major histocompatibility complex (MHC) molecule. A companion study, solving the crystal structure of T22, highlights the differences between this interaction and those of classical MHC molecules and alphabeta T cells.

Alpha beta and gamma delta T cells can share a late common precursor.

BACKGROUND: The subdivision of T cells into alpha beta and gamma delta subtypes is conserved throughout vertebrate development. The respective alpha beta and gamma delta T-cell receptors (TCRs) are encoded by somatically rearranged genes. There has been broad speculation as to whether an individual thymocyte can become either a gamma delta T cell or an alpha beta T cell as a result of stochastic gene rearrangement processes, or whether the two types of T cell are derived from separate lineages. Many of the experimental findings are apparently conflicting, however, and the issue--a basic one in immunology and development--remains unresolved. RESULTS: To address this issue, we have used the recently developed polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique, which allows us to examine quantitatively the status of TCR gamma and delta genes in postnatal alpha beta T cells and their progenitors. Interestingly, such cells are depleted of productively rearranged delta and gamma genes, which can encode delta and gamma TCR polypeptide chains. However, in mice that can rearrange TCR delta gene segments, but in which the TCR delta gene is non-functional in other respects, no such depletion of productive rearrangements is seen. CONCLUSION: The quantitative data that we have obtained fulfill the predictions of the stochastic hypothesis: that is, a progenitor T cell first attempts to become a gamma delta T cell and, if unsuccessful, then attempts to become an alpha beta T cell. Thus, alpha beta and gamma delta T cells can derive from a common precursor thymocyte. In the simplest case, therefore, lineage-determining factors are the successful rearrangement of both gamma and delta genes before TCR alpha gene rearrangements occur, which lead to deletion of the TCR delta locus and thereby preclude further gamma delta T-cell differentiation. In contrast, successful rearrangement of the TCR beta locus remains compatible with cells becoming either gamma delta or alpha beta T cells.