Lack of B cell leakiness in BALB/cA-nu, scid double mutant mice.

Central Institute for Experimental Animals, 1430 Nogawa, Kawasaki 216, Japan.

BALB/cA mice homozygous for both nu and scid mutations (BALB/cA-nu/nu, scid/scid) were developed by mating between BALB/cA-scid and BALB/cA-nu. These mice have greater longevity than C.B-17-scid because no thymic lymphoma occurs in them unlike in the latter. C.B-17-scid is known to show the leaky phenomenon in which a few clones of functional T and B cells develop in aged C.B-17-scid. Unexpectedly, the leaky B cells and T cells were absent or suppressed in BALB/cA-nu, scid mice when cytokine expressions were determined by RT-PCR, lymphocyte phenotypes by flow cytometry and serum immunoglobulin levels by ELISA. These results indicate that B cell leakiness may be induced by leaked T cells. BALB/cA-nu, scid mice may be useful as a recipient in allo- and xeno-transplantation experiments because of the absence of both thymic lymphomas and leakiness, in addition to lack of hair.

PMID: 11326425 [PubMed - indexed for MEDLINE]

Melanoma immunotherapy by targeted IL-2 depends on CD4(+) T-cell help mediated by CD40/CD40L interaction.

The Scripps Research Institute, Department of Immunology, La Jolla, California 92037, USA.

The induction of tumor-protective immunity against malignancies remains a major challenge in cancer immunotherapy. A novel, humanized anti-ganglioside-GD(2)-IL-2 immunocytokine (hu14.18-IL-2) induced CD8(+) T cells to eradicate established pulmonary metastases of B78-D14 murine melanoma, in a process that required help by CD4(+) T cells and was mediated by the CD40/CD40 ligand (CD40L) interaction. The anti-tumor effect was diminished in mice deficient in CD4(+) T-cells. Three lines of evidence show that CD4(+) T-cell help was mediated by CD40/CD40L interaction but not by endogenous IL-2 production. First, the hu14.18-IL-2-induced anti-tumor response is partially abrogated in C57BL/6J CD40L knockout (KO) mice in contrast to C57BL/6J IL-2 KO animals, in which the immunocytokine was completely effective. Second, partial abrogation of the anti-tumor effect is induced with anti-CD40L antibodies to the same extent as with CD4(+) T-cell depletion. Third, a complete anti-tumor response induced by hu14.18-IL-2 can be reconstituted in C57BL/6J CD40L KO mice by simultaneous stimulation with an anti-CD40 mAb. These results suggest that help provided by CD4(+) T cells via CD40/CD40L interactions in our tumor model is crucial for effective immunotherapy with an IL-2 immunocytokine.

PMID: 10841521 [PubMed - indexed for MEDLINE]

PMCID: PMC300854

Antibody-IL-12 fusion proteins are effective in SCID mouse models of prostate and colon carcinoma metastases.

Lexigen Pharmaceuticals Corp., Lexington, MA 02137, USA. sgillies@lexigenpharm.com

IL-12 is a complex cytokine in both its structure and its range of biologic activities. Fusions of this heterodimeric molecule with an intact antitumor Ab were made to test the feasibility and efficacy of targeting IL-12 to tumors to elicit a local immune response. Fusion proteins composed of the human p35 and p40 subunits had IL-12 bioactivities that were nearly as potent on human immune cells as the rIL-12 standard, but were inactive on mouse cells. Hybrid IL-12 fusion proteins composed of mouse p35 and human p40, fused to Ab, were capable of inducing IFN-gamma, but were much less active on mouse spleen cells than a mouse IL-12 standard. Despite this relatively low activity, the hybrid fusion protein was as effective in a SCID mouse model as a fully active Ab-IL-2 fusion protein in eliminating established pulmonary metastases of CT26 colon carcinoma. Specific targeting of a human IL-12 fusion protein to metastatic prostate carcinoma xenografts was also shown to be effective in SCID mice transplanted with human lymphocyte-activated killer cells. These results demonstrate the importance of directing this potent cytokine to the tumor microenvironment and suggest an important alternative to systemic IL-12 administration or gene therapy for increasing its therapeutic index.

PMID: 9637539 [PubMed - indexed for MEDLINE]

Activated natural killer cells suppress myelopoiesis in mice with severe combined immunodeficiency.

Department of Immunology, Karolinska Institute, Stockholm, Sweden.

The in vivo effect of natural killer (NK) cell activation on autologous myelopoiesis was studied in an environment deficient of functional T and B cells. Administration of 3,6-bis[2-(Dimethylamino)-ethoxy]-9H-xanthen-9-one dihydrochloride) Tilorone) or recombinant interleukin-2 (rIL-2) to mice with severe combined immunodeficiency (C.B.-17 scid/scid) resulted in an increase in YAC-1 lysis by their splenocytes as well as bone marrow cells. Recombinant IL-2 furthermore led to a fivefold increase in the cellularity of the spleen. When assayed against human NK/lymphokine-activated killer (LAK) target, K562 cell line, the IL-2-activated mouse cells exhibited no cytotoxicity across the species barrier. Both agents induced a profound suppression of myelopoietic progenitor cells as measured in a 7-day granulocyte-macrophage colony forming cell (GM-CFC) assay. We conclude that the presence of neither functional T nor B cells is necessary for NK cells to mediate inhibition of myelopoiesis in the autologous host.

PMID: 8469936 [PubMed - indexed for MEDLINE]

Functional and phenotypic analysis of thymocytes in SCID mice. Evidence for functional response transitions before and after the SCID arrest point.

Division of Biology, California Institute of Technology, Pasadena 91125.

Thymocytes from severe combined immune deficient (SCID) mice undergo developmental arrest at an early stage, before most TCR gene rearrangement. They therefore represent a natural test case to assess those aspects of T cell development that are TCR independent. Multiparameter flow cytometry was used to analyze the array of immature phenotypes present in the SCID thymus at steady state, as defined by the markers CD4, CD5, Sca-1, NK1.1, CD44, heat-stable antigen (HSA), and IL-2R alpha. The results suggest a simple developmental block in SCID mice rather than a program of aberrant differentiation. SCID thymocytes displayed efficient, developmentally regulated functional responses. Approximately 20-25% of the cells, mostly within the IL-2R alpha +HSA+CD44low fraction, could be induced to express IL-2. This IL-2 inducibility was highly dependent on IL-1 costimulation, in agreement with the behavior of normal immature thymocytes. These results formally demonstrate that competence to express IL-2 is developed independently of TCR expression or gene rearrangement. Comparison of the response properties of various SCID thymocyte subsets indicated that IL-2 inducibility is first likely to be acquired at an early (Sca-1++CD44++HSAlow) stage. A later functional transition was revealed by comparing patterns of IL-2R alpha regulation in normal and SCID IL-2R alpha +HSA+CD44low thymocytes. The SCID thymocytes uniformly maintained IL-2R alpha expression on in vitro stimulation, whereas only a minority of the normal cells in the corresponding subset could do so unless IL-1 was also added. The SCID arrest point thus appears to separate the IL-2R alpha +HSA+CD44low stage into distinct early (TCR independent) and late phases. Normal cells that progress beyond the SCID arrest point appear to lose, rather than gain, competence to make various responses, even before they leave the IL-2R alpha +HSA+CD44low stage. A model is proposed in which discrete changes in functional competence define novel transitions in early thymocyte development, at least some of which may be linked to TCR-beta gene rearrangement before positive or negative selection.

PMID: 8376791 [PubMed - indexed for MEDLINE]

Low-dose interleukin 2 prevents the development of Epstein-Barr virus (EBV)-associated lymphoproliferative disease in scid/scid mice reconstituted i.p. with EBV-seropositive human peripheral blood lymphocytes.

Department of Medicine, Roswell Park Cancer Institute, Buffalo, NY 14263-0001.

When severe combined immune deficient (SCID) mice undergo i.p. injection with peripheral blood lymphocytes from normal human donors seropositive for EBV, a majority of these mice (hu-PBL-SCID mouse model) subsequently develop a fatal EBV+ lymphoproliferative disease (EBV-LPD) of human B-cell origin. Because T cells normally are critical in the control of EBV infection, we hypothesized that human T-cell dysfunction accounts for EBV-LPD in the hu-PBL-SCID mouse and that systemic administration of T-cell-derived cytokines would reestablish protective immunity against EBV-LPD. We show that the daily s.c. administration of a very low dose (500 international units) of polyethylene glycol-modified recombinant human interleukin 2 (PEG-IL-2) to hu-PBL-SCID mice can prevent the development of fatal EBV-LPD and significantly improves survival (78%), compared with the survival of hu-PBL-SCID mice treated with placebo (20%, P = 0.0008). Additional lymphocyte-depletion experiments showed that mouse natural killer cells and human CD8+ T cells provided cellular immunity necessary for the PEG-IL-2-mediated protective effect, whereas i.p. injection of human peripheral blood lymphocytes depleted of CD4+ T cells had no adverse effect when combined with PEG-IL-2 therapy and may have been beneficial. These data establish that very low-dose PEG-IL-2 therapy can overcome the immune deficiencies that lead to EBV-LPD in the hu-PBL-SCID mouse and point to the usefulness of this model for evaluating cytokine therapies in EBV-LPD. The use of low-dose IL-2 as a preventative immune therapy has potential application in immunocompromised individuals at high risk for EBV-LPD.

PMID: 7911241 [PubMed - indexed for MEDLINE]

PMCID: PMC44039

Tumorigenicity of human T-cell leukemia virus type I-infected cell lines in severe combined immunodeficient mice and characterization of the cells proliferating in vivo.

First Department of Internal Medicine, Kyoto University, Japan.

The mechanism involved in leukemogenesis and neoplastic cell growth of adult T-cell leukemia (ATL) still remains unclear. We examined the tumorigenicity of human T-cell leukemia virus type I (HTLV-I)-infected cell lines in an in vivo cell proliferation model using severe combined immunodeficient (SCID) mice. Eleven HTLV-I-infected cell lines were injected into SCID mice and we found that 4 of them were capable of proliferating in SCID mice. Three of four transplantable cell lines are derived from the leukemic cell clone and 6 of 6 HTLV-I-infected cell lines of nonleukemic cell origin could not engraft in SCID mice. Interestingly, it was shown that some HTLV-I-infected and interleukin-2 (IL-2)-dependent cell lines could successfully engraft in SCID mice. The expression of IL-2 mRNA was not detected in these cell lines growing either in vivo or in vitro. HTLV-I viral products were not detected in 3 of 4 transplantable cell lines proliferating in vivo. Peripheral blood T cells immortalized by introduction of tax gene of HTLV-I were found to have no tumorigenic potential in SCID mice. These data suggest that (1) HTLV-I-infected cell lines of nonleukemic cell origin do not have enough leukemogenic changes to acquire the tumorigenic potential in SCID mice; (2) the IL-2 autocrine mechanism is not directly involved in the tumor cell growth; (3) viral gene expression is not needed for the maintenance of neoplastic cell growth; and (4) the expression of tax gene is not sufficient for the neoplastic cell growth in vivo.

PMID: 7662981 [PubMed - indexed for MEDLINE]