T cell receptor expression by T cells that mature extrathymically in nude mice

Antibody treatment of human tumor xenografts elicits active anti-tumor immunity in nude mice

Athymic nude mice bearing subcutaneous tumor xenografts of the human anti-colorectal cancer cell line SW480 were used as a preclinical model to explore anti-tumor immunotherapies. Intratumor or systemic treatment of the mice with murine anti-SW480 serum, recombinant anti-SW480 polyclonal antibodies, or the anti-colorectal cancer monoclonal antibody CO17-1A, caused retardation or regression of SW480 tumor xenografts. Interestingly, when mice that had regressed their tumors were re-challenged with SW480 cells, these mice regressed the new tumors without further antibody treatment. Adoptive transfer of spleen cells from mice that had regressed their tumors conferred anti-tumor immunity to naïve nude mice. Pilot experiments suggest that the transferred anti-tumor immunity is mediated by T cells of both gammadelta and alphabeta lineages. These results demonstrate that passive anti-tumor immunotherapy can elicit active immunity and support a role for extra-thymic gammadelta and alphabeta T cells in tumor rejection. Implications for potential immunotherapies include injection of tumor nodules in cancer patients with anti-tumor antibodies to induce anti-tumor T cell immunity.

T-cell and natural killer cell development in thymectomized Xenopus

The Xenopus early-thymectomy model system is used to investigate the extent to which the thymus controls T-cell development and to probe the evolution of natural killer (NK) cells. Loss of T-cell function following thymectomy, together with the paucity of cells expressing monoclonal antibody-defined T-cell surface markers, and greatly reduced expression of T-cell receptor beta transcripts in spleen, liver and intestine, indicate that T-cell development in minimal in the absence of the thymus. Our findings therefore mitigate against the idea that a substantial extrathymic pathway of T-cell development exists in early vertebrate evolution. Rather, they suggest that in this amphibian representative T cells are predominately thymus dependent. In vitro studies with control and thymectomized Xenopus splenocytes reveal that a non-T/non-B population and also two T-cell subsets all display natural cytotoxicity towards allogeneic thymus lymphoid tumour cells (which are deficient in MHC antigen expression). Since Xenopus thymectomized early in larval development are permanently deficient in T cells, they may provide a useful phylogenetic model for the study of NK cells.

Normalization of the peripheral blood T cell receptor V beta repertoire after cultured postnatal human thymic transplantation in DiGeorge syndrome

Complete DiGeorge syndrome is an immunodeficiency disease characterized by thymic aplasia and the absence of functioning peripheral T cells. A patient with this syndrome was transplanted with cultured postnatal human thymic tissue. Within 5 weeks of transplantation, flow cytometry, T cell receptor V beta sequence analysis, and cell function studies showed the presence of oligoclonal populations of nonfunctional clonally expanded peripheral T cells that were derived from pretransplantation T cells present in the skin. However, at 3 months posttransplantation, a biopsy of the transplanted thymus showed normal intrathymic T cell maturation of host T cells with normal TCR V beta expression on thymocytes. By 9 months postransplantation, peripheral T cell function was restored and the TCR V beta repertoire became polyclonal, coincident with the appearance of normal T cell function. These data suggest that the transplanted thymus was responsible for the establishment of a new T cell repertoire via thymopoiesis in the chimeric thymic graft.

Cytotoxicity and proliferation of splenocytes and lymph node cells from adjuvant-treated nude mice. Studies of natural and in vitro activation

The cytotoxicity of NK cells and lymphocytes derived from nonadherent splenocytes (SPL) and regional lymph node cells (LNC) from complete Freund's adjuvant (CFA)-treated athymic nude young (4-6 weeks) and aged (over 1 year) BALB/c nu/nu mice in vitro activated with rIL-2, anti-CD3 mAb or PPD was analyzed and compared to SPL and LNC from age-matched euthymic BALB/c mice. The high natural cytotoxicity to YAC-1 target cells of SPL or LNC could be augmented by 48 h stimulation in vitro with rIL-2, especially when derived from young nude BALB/c mice. The increase in cytotoxic activity was accompanied by increased proliferative activity of both SPL and LNC, which showed statistically significant differences between the rates of stimulation of cells from the young and aged groups. Anti-CD3 mAb strongly activated the cytotoxicity of BALB/c euthymic donor effector cells against P-815 target cells, corresponding to a very high proliferative activity of these cells, but anti-CD3 mAb did not lead to activation of effector cells from nude donors. FACS analyses of antigenic markers similarly showed an increased number of T cells in LNC from aged BALB/c nude donors, which, however, never reached the levels of those of euthymic animals.

Dextran sulfate sodium (DSS) induced experimental colitis in immunodeficient mice: effects in CD4(+) -cell depleted, athymic and NK-cell depleted SCID mice

Administration of dextran sulfate to mice, given in the drinking water results in acute or subacute colonic inflammation, depending on the administration protocol. This colonic inflammation exhibits ulceration, healing and repair, and a therapeutic response that makes it valuable for the study of mechanisms that could act in the pathogenesis of human ulcerative colitis, a disease thought to have an immunologically dependent pathogenesis. To investigate if immunological mechanisms were involved in the induction of colonic inflammation in this model, mice with different degrees of immunodeficiency were used. It was shown that dextran sulfate induced colitis could be induced in Balb/c mice depleted of CD4(+) helper T cells by treatment with monoclonal antibodies preceded by adult thymectomy. The depletion of CD4(+) was verified by flow cytometric analysis. Furthermore, the colonic inflammation could equally be induced in athymic CD-1 nu/nu mice lacking thymus-derived T cells, in T and B-cell deficient SCID mice, and also in SCID mice depleted of NK cells by treatment with anti-asialo GM1 antibodies. The NK-cell depletion was verified by measuring spleen NK-cell activity. The resulting colonic inflammation in all these types of deficient mice was qualitatively comparable, as shown by clinical and histological appearance. These results indicate that the presence of functional T, B and NK cells is not crucial for the induction of dextran sulfate colitis in mice.

GM-CSF is required for the Pseudomonas exotoxin A-induced proliferation of immature T cells in athymic mice

Previous studies have demonstrated that Pseudomonas exotoxin A stimulated the proliferation of immature T lymphocytes within the splenocytes of athymic mice. These studies were performed to determine which lymphokines were involved in the proliferation of the immature T cells. The results of this study indicate that exotoxin A does not induce the production of interleukin-2 or tumor necrosis factor from B cell-depleted splenotypes from athymic mice. However, exotoxin A does induce the production of granulocyte-macrophage colony-stimulating factor (GM-CSF) from B cell-depleted splenocytes. Furthermore, the GM-CSF was shown to be produced by a Thy1+, CD4-, CD8- T lymphocyte. The addition of anti-GM-CSF antibody abrogates the exotoxin A-induced proliferation of B cell-depleted splenocytes from athymic mice. Thus, these data indicate that exotoxin A induces the production of GM-CSF from immature T lymphocytes within the splenocytes of athymic mice and the exotoxin A-induced proliferation of these immature T cells is dependent on the presence of GM-CSF.

Cytotoxic cells in immunodeficient athymic mice

A studies of cytotoxic cells in athymic nude mice demonstrate higher cytotoxic activity of NK cells and macrophages than in their euthymic counterparts. The higher level of endogenous cytotoxic activity can be considered as complementary to the deficiency or lack of thymus dependent T lymphocytes and their functions. However, with increased age of mice some T lymphocytes and their functions can be demonstrated. By stimulation of splenocytes and lymph node cells in vitro with IL-2 or anti CD3 antibody cytotoxic activity towards P-815 (NK resistant, LAK sensitive) target cells can be generated. There exist data, which indicate that the cytotoxic activity is exerted by extrathymic pre-T lymphocytes with TcR gamma delta antigenic phenotype. The differences in transplantability of human tumors in athymic nude mice cannot be explained by defect in antigen recognition and in immune response of athymic nude mice, recipients of the xenografted material. The biological relevance in vivo of high endogenous cytotoxicity of NK cells observed in many strains of athymic nude mice remains obscure. The availability of new immunodeficient mouse models, e.g. scid mice deficient in B and T lymphocytes and with low level of NK cells, in which not only xenografted human tumor grow but human lymphoid cell can be transplanted as well, opens new and broader experimental possibilities, in which new preclinical immunotherapeutical approaches can be applied.

Lipopolysaccharide from Brucella abortus behaves as a T-cell-independent type 1 carrier in murine antigen-specific antibody responses

In order to determine the carrier nature of lipopolysaccharide from Brucella abortus (LPS-BA) in evoking humoral responses, normal and immunodeficient mice were immunized with trinitrophenyl (TNP)-conjugated LPS-BA (TNP-LPS-BA) and the responses were compared with those to known T-dependent and T-independent antigens. TNP-LPS-BA, like T-independent type 1 (TI-1) antigens such as TNP-BA and TNP-LPS from Escherichia coli (TNP-LPS-EC), generated anti-TNP responses in BALB/c, athymic BALB/c nu/nu, and CBA/N mice. In contrast, N-2,4-dinitrophenyl-beta-alanylglycylglycyl-substituted keyhole limpet hemocyanin, a typical T-dependent antigen, was not immunogenic in athymic mice, and TNP-Ficoll (T-independent type 2) was ineffective in eliciting humoral responses in CBA/N mice. These results indicate that LPS from B. abortus acts as a TI-1 carrier in generating antibody responses. In C3H/HeJ mice, TNP-LPS-BA generated higher-titer immunoglobulin G1 (IgG1), IgG2a, and IgG2b anti-TNP antibodies than TNP-LPS-EC. Compared with those from BALB/c mice, pure resting B cells isolated from C3H/HeJ mice exhibited a 30-fold lower proliferative response to LPS-EC, whereas the LPS-BA response was reduced to a lesser extent (5-fold). This suggests that the disparity observed in antibody titers was due to different abilities of LPS from B. abortus and E. coli to stimulate C3H/HeJ B cells. The ability of LPS from B. abortus to act as a carrier in generating humoral immune responses indicates that LPS-BA can be substituted for whole B. abortus organisms in vaccine development.

Nephrotoxic serum nephritis in nude rats: the roles of host immune reactions in the accelerated type

By immunization with rabbit immunoglobulins and the injection of a subnephritogenic dose of rabbit nephrotoxic serum (NTS), accelerated-type nephrotoxic serum nephritis (NTN) was induced in heterozygous (rnu/+) rats but not in athymic nude (rnu/rnu) rats. By transferring rat antibody against rabbit immunoglobulins, marked proteinuria was induced also in nude rats (202.0 +/- 98.4 mg/day on day 3) as in rnu/+ rats (122.6 +/- 35.3 mg/day on day 3). No marked differences in histological findings could be found between both groups. The most marked increase in the number of intraglomerular infiltrating cells was observed in heterozygous rats indicating that the presence of thymus-derived cells leads to the accumulation of more cells in glomeruli. We conclude that humoral immunity alone is enough to accelerate the pathogenic mechanism which induces glomerular injury with heavy proteinuria in this model.

Bone marrow cells of athymic nude mice express functional T cell receptor alpha chain transcripts rearranged to V delta 2, 3, 4, 5, 6 genes

From bone marrow cells (BMC) of athymic nude mice, T cell receptor (TcR) alpha chain transcripts were selectively amplified by polymerase chain reaction (PCR) using V delta 2-, V delta 3-, V delta 4-, V delta 5-, V delta 6- and C alpha-specific primers. Amplified DNA fragments were cloned, and 32 randomly selected clones from 5 PCR were sequenced. Twenty-three distinct rearrangement events were detected, of which 87% (20/23) were in-frame. All five tested V delta genes (V delta 2, 3, 4, 5, 6) rearranged in-frame to J alpha-C alpha. N-region diversity in V delta-J alpha junctions present in most clones was limited to two to five nucleotides. P-nucleotide additions in this region were also detected. The V delta 5 gene located 3' of C delta in reversed transcriptional orientation was rearranged to J alpha by inversion. The J alpha usage pattern of the sequenced clones was strongly biased towards rearrangement of the most 5' genes (located nearest to C delta) of the J alpha cluster: the most 5' J alpha (J alpha TA1) was used by 30% of all clones, and 78% of all J alpha rearranged to V delta were located in the 5' 12 kb of the 60-kb J alpha cluster. As distinct V delta/C delta and V alpha/C alpha TcR usage patterns are prevalent in peripheral T cell populations, our data suggest that these TcR usage patterns results from repertoire selections operating in alpha beta and gamma delta T cell lineages, but not from preferential V delta-C delta and V alpha-C alpha rearrangement patterns.

Extrathymic positive selection of αβ T-cell precursors in nude mice

T lymphocytes expressing alpha beta T-cell receptors with sufficient affinity to major histocompatibility complex (MHC) molecules expressed on thymus epithelial cells are positively selected and mature to functional T cells. But several studies have demonstrated that athymic nude mice grafted with MHC-incompatible thymuses developed T cells specific for nude host rather than thymic MHC. We examined this paradox by analysing the specificity of T lymphocytes derived from nude mice. We report here that nude T lymphocyte precursors transferred to allogeneic SCID (severe combined immunodeficiency) mice with a functioning thymus (but lacking T or B cells) generated host MHC-restricted effector T cells but also contained T cells restricted to donor MHC. If nude T cells were depleted from nude lymphohaemopoietic donor cells before or after transfer, only host MHC-specific T cells matured. The results may explain the unusual MHC specificities of nude T lymphocytes described in earlier studies and demonstrate two separate differentiation steps: in nude mice, T cells may be positively selected for self-MHC restriction specificity extrathymically; then a functional thymus is required for efficient T cell maturation.

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.