Rearrangement patterns of T-cell receptor genes in the spleen of athymic (nu/nu) young mice

Intracranial glioblastoma models in preclinical neuro-oncology: neuropathological characterization and tumor progression

Although rodent glioblastoma (GBM) models have been used for over 30 years, the extent to which they recapitulate the characteristics encountered in human GBMs remains controversial. We studied the histopathological features of dog GBM and human xenograft GBM models in immune-deficient mice (U251 and U87 GBM in nude Balb/c), and syngeneic GBMs in immune-competent rodents (GL26 cells in C57BL/6 mice, CNS-1 cells in Lewis rats). All GBMs studied exhibited neovascularization, pleomorphism, vimentin immunoreactivity, and infiltration of T-cells and macrophages. All the tumors showed necrosis and hemorrhages, except the U87 human xenograft, in which the most salient feature was its profuse neovascularization. The tumors differed in the expression of astrocytic intermediate filaments: human and dog GBMs, as well as U251 xenografts expressed glial fibrillary acidic protein (GFAP) and vimentin, while the U87 xenograft and the syngeneic rodent GBMs were GFAP(-) and vimentin(+). Also, only dog GBMs exhibited endothelial proliferation, a key feature that was absent in the murine models. In all spontaneous and implanted GBMs we found histopathological features compatible with tumor invasion into the non-neoplastic brain parenchyma. Our data indicate that murine models of GBM appear to recapitulate several of the human GBM histopathological features and, considering their reproducibility and availability, they constitute a valuable in vivo system for preclinical studies. Importantly, our results indicate that dog GBM emerges as an attractive animal model for testing novel therapies in a spontaneous tumor in the context of a larger brain.

Peripheral CD4 T-Cell Depletion Is Not Sufficient to Prevent Ischemic Acute Renal Failure

BACKGROUND

Ischemia reperfusion injury leading to acute renal failure (ARF) and delayed graft function is an important problem in organ transplantation. CD4+ T cells, essential for transplant rejection, may mediate ischemic ARF. We have demonstrated that the caspase-1 mediated production of IL-18 is pathogenic in ischemic ARF in mice. A potential source of IL-18 in ischemic ARF is the CD4+ T cell. We therefore examined the effect CD4+ T cell depletion on the development of ischemic ARF and the activation of IL-18.

METHODS

Functional and histological correlates were examined in two groups of mice with ischemic ARF: 1) CD4 T-cell depleted with the antibody GK1.5, and 2) T-cell receptor alpha-chain deficient (TCRalpha -/-) mice. TCRalpha -/- mice lack the alpha chain of the T-cell receptor and therefore lack functional CD4+ and CD8+ T cells.

RESULTS

Flow cytometry of lymph nodes and immunohistochemistry of kidneys demonstrated complete depletion of CD4+ T cells in mice with ischemic ARF treated with GK 1.5. CD4+ T-cell depletion did not confer functional (serum creatinine, BUN and FITC-labeled inulin clearance) or histological protection against ischemic ARF. Likewise, TCRalpha -/- mice were not protected against ischemic ARF. Renal caspase-1 activity and IL-18 protein were similar in CD4+ T-cell depleted and wild-type postischemic reperfusion.

CONCLUSIONS

Ischemic ARF can occur in the absence of classical T-cell function. The evaluation of other inflammatory mediators (e.g., macrophages or NK cells) as a source of IL-18 and mediator of ischemic ARF warrants further investigation.

A lack of DNA mismatch repair on an athymic murine background predisposes to hematologic malignancy

Inheritance of a germline mutation in one of the DNA mismatch repair genes predisposes human individuals to hereditary nonpolyposis colorectal cancer, characterized by development of tumors predominantly in the colon, endometrium, and gastrointestinal tract. Mice heterozygous for a mismatch repair-null mutation generally do not have an increased risk of neoplasia. However, mice constitutively lacking mismatch repair are prone to tumor development from an early age, particularly thymic lymphomas. Mismatch repair-deficient mice crossed to Apc(+/-) mice develop an increased spontaneous intestinal tumor incidence, demonstrating that the tumor spectrum can be genetically influenced. Here, we bred Msh2- and Msh6-deficient mice to athymic nude mice, hypothesizing that a broader tumor spectrum may be observed if mice are able to survive longer without succumbing to thymic lymphomas. However, Msh2(-/-);Foxn1(nu/nu) and Msh6(-/-);Foxn1(nu/nu) mice developed primarily early-onset lymphoblastic lymphomas. Using B-cell-specific markers, we found these tumors to be predominately B-cell in origin. The development of hematologic malignancy in the mouse, even in the absence of a thymus, parallels the development of B- and T-cell lymphoma and leukemia in the few rare mismatch repair-null human patients that have been identified. The persistent development of hematologic malignancy both in the mouse and in human patients deficient in mismatch repair leads us to implicate mismatch repair as an important repair mechanism in normal B- and T-cell development. Thus, mismatch repair-deficient mice may prove to be a good model to study human hematologic malignancy.

Allelic loss on chromosome 4 (Lyr2/TLSR5) is associated with myeloid, B-lympho-myeloid, and lymphoid (B and T) mouse radiation-induced leukemias

The CBA/H mouse model of radiation-induced acute myeloid leukemia (AML) was re-examined using molecular approaches. In addition to the typical promyelocytic AMLs, 34% were reclassified as early pre-B lympho-myeloid leukemias (L-ML) based on leukemic blood cell morphology, immunoglobulin heavy-chain gene re-arrangements (IgH(R)), or expression of both lymphoid (Vpre-B1 and Rag1) and myeloid (myeloperoxidase and lysozyme M) genes. Allelic loss on chromosome 4 was frequently detected in AMLs (53%) and L-MLs (more than 95%), and the preferential loss of the maternally transmitted allele suggests the locus may be imprinted. A minimally deleted region (MDR) maps to a 3.4-cM interval, which is frequently deleted in radiation-induced thymic lymphomas (TLSR5) and contains a recessive, maternally transmitted genetic locus (Lyr2) that confers resistance to spontaneous and radiation-induced pre-B and T cell lymphomas, suggesting they are one and the same. Thus, the Lyr2/TLSR5 locus is frequently implicated in myeloid, lymphoid (B and T), and mixed-lineage mouse leukemias and lymphomas. Epigenetic inactivation of one Lyr2/TLSR5 allele during normal mouse development suggests that only a single hit is required for its inactivation during leukemogenesis, and this may be a significant contributing factor to the efficiency of the leukemogenic process in the mouse.

Hepatosplenic and subcutaneous panniculitis-like gamma/delta T cell lymphomas are derived from different Vdelta subsets of gamma/delta T lymphocytes

Gamma/delta T cell lymphomas (gamma/delta TCL) represent rare, often aggressive types of T cell malignancy that are clinically and pathologically diverse. Most gamma/delta TCL occur as a hepatosplenic or subcutaneous type. To date, analysis of the T cell receptor delta (TCRS) gene repertoire of hepatosplenic gamma/delta TCL (gamma/delta HSTCL) and subcutaneous panniculitis-like gamma/delta TCL (gamma/delta SPTCL) has been reported only in a limited number of cases. In this study we analyzed 11 gamma/delta HSTCL and 4 gamma/delta SPTCL by polymerase chain reaction and immunostaining to determine their usage of the Vdelta subtypes (Vdelta1-6). It is noteworthy that 10 of 11 gamma/delta HSTCL expressed the Vdelta1 gene. The remaining case also expressed T cell receptor delta (TCRS) as determined by flow cytometry and TCRdelta rearrangement in Southern blot. However, the Vdelta gene expressed by this lymphoma could not be determined, which suggests usage of an as yet unidentified Vdelta gene. In striking contrast to the gamma/delta HSTCL, all 4 gamma/delta SPTCL expressed the Vdelta2 gene. Our data demonstrate that gamma/delta HSTCL are preferentially derived from the Vdelta1 subset of gamma/delta T lymphocytes, whereas gamma/delta SPTCL are preferentially derived from the Vdelta2 subset. The pattern of Vdelta gene expression in HSTCL and SPTCL corresponds to the respective, predominant gamma/delta T cell subsets normally found in the spleen and skin. This finding suggests that gamma/delta TCL are derived from normal gamma/delta T lymphocytes which reside in the affected tissues. Furthermore, the selective, lymphoma type-specific Vdelta gene segment usage may provide a molecular tool to distinguish better among various types of gamma/delta TCL lymphoma particularly in the clinically advanced, widely disseminated cases.

Adenovector-Mediated Expression of Human Thrombopoietin cDNA in Immune-Compromised Mice: Insights into the Pathophysiology of Osteomyelofibrosis

Thrombopoietin (TPO) cDNA can be effectively delivered in vivo by adenovectors. Immune normal mice (BALB/c) and syngeneic mice with variable degrees of immune dysfunction nu, SCID, and NOD-SCID) were treated with an adenovirus vector expressing the human TPO cDNA (AdTPO). Platelet peaks were significantly higher in SCID and NOD-SCID mice compared with BALB/c and nu mice. Human plasma TPO concentration correlated with the platelet counts. SCID and NOD-SCID mice exhibited also granulocytosis and increased numbers of hemopoietic progenitors in bone marrow. Following platelet peak, BALB/c mice developed autoantibodies against murine TPO leading to thrombocytopenia and depletion of megakaryocytes and hemopoietic progenitors in bone marrow. AdTPO-treated SCID mice developed osteomyelofibrosis and extramedullary/extrasplenal hemopoiesis. In contrast, NOD-SCID mice with a similar magnitude of TPO overexpression did not show fibrotic changes in bone marrow. We conclude, first, that a chronic high level of TPO overexpression stimulates megakaryocytopoiesis and myelopoiesis leading to thrombocytosis and granulocytosis. Second, increased megakaryocytopoiesis is not sufficient for development of secondary osteomyelofibrosis. The functionally deficient monocytes and macrophages of NOD-SCID mice probably prevented fibrotic marrow changes. Third, immune deficiency enhances expression of adenovirally mediated transgenes, and fourth, xenogeneic transgene delivered by adenovector to a host with normal immune functions may induce loss of immune tolerance and autoimmune phenomenon.

Skewed T-cell receptor Vbeta8.2 expression in transgenic CD2-myc induced thymic lymphoma: a role for antigen stimulation in tumour development?

Transgenic mice expressing the c-myc proto-oncogene under the control of the CD2-dominant control region show stochastic development of mainly clonal thymic lymphoma with long latency, indicating that cooperative events are needed for the development of the fully malignant phenotype. Previous studies have suggested that T-cell receptor-associated signals can contribute to tumour development. We have therefore used this transgenic model of T-cell transformation to determine whether antigen-specific responses could constitute an epigenetic event in lymphomagenesis. The T-cell receptor (TcR) repertoires of lymphoma clones were analysed with a panel of monoclonal antibodies (Abs) recognizing TcR Vbeta chains. The Vbeta repertoire of tumour clones arising in these mice was non-random with overrepresentation of Vbeta8.2 TcR species. The majority of Vbeta8.2+ clones were of a mature CD3+ CD8 single-positive (SP) phenotype. The biased TcR usage, together with a mature cell phenotype is consistent with the hypothesis that TcR-mediated signals cooperate with activated myc during T-cell transformation.

T cells with dual antigen specificity in T cell receptor transgenic mice rejecting allografts

Allelic exclusion of T cell receptor (TCR) genes is incomplete: a significant percentage (10-30%) of normal human and mouse peripheral T cells express two surface TCR alpha chains, and a small percentage of peripheral human T cells have been reported to express two surface TCR beta chains. A proportion of thymocytes in TCR transgenic mice rearrange endogenous T cell receptor genes, and peripheral T cells with two TCR alpha chains, transgenic and endogenous, have been reported. T cell clones with more than a single TCR heterodimer on their surface might be expected to show specificity for more than one cognate antigen: we report here a T cell clone with dual antigen specificity, isolated from an F5 TCR influenza nucleoprotein (NP 366-374/Db)-specific transgenic female mouse which had rejected an H-2-matched male skin graft. It was selected in vitro by stimulation with male H-2b spleen cells in the absence of the NP366-374 peptide but has specificity for both H-Y/Db and NP366-374. This contrasted with the single NP366-374/Db specificity shown by a control clone isolated from a Rag1-/- F5 mouse. The dual antigen specificity was associated with the rearrangement of endogenous TCR genes and cell surface expression of these as well as the TCR transgene.

Cellular aspects of early T-cell development

Although the nature of the precursor cells seeding the thymus is still uncertain, their immediate progeny in the adult murine thymus have now been isolated. These lymphoid-restricted, prothymocyte-like cells express CD4, but neither CD4 nor CD8 seem to be involved in the early steps of T-cell development. Cytokines produced by stromal cells are likely to be involved in intrathymic T-cell development, but interleukin-2 and interleukin-4 do not appear to be required. There is still no satisfactory cell-culture model of intrathymic T-cell development. Current culture systems reflect only fragments of the process, or are models of extrathymic developmental pathways.