Role of Interferon-Gamma in Interleukin 12-Induced Pathology in Mice

Interleukin 12 (IL-12) activates natural killer (NK) and T cells with the secondary synthesis and release of interferon-gamma (IFN-gamma) and other cytokines. IL-12-induced organ alterations are reported for mice and the pathogenetic role of IFN-gamma is investigated by the use of mice deficient in the IFN-gamma receptor (IFN-gamma R(-/-)). IL-12 caused a rapid infiltration of liver and splenic red pulp with activated macrophages; this and increased NK cells resulted in a fivefold increase of splenic weight in wild-type mice. Splenomegaly was associated with myelosuppression and decreasing peripheral leukocyte counts. IL-12-induced changes in wild-type mice were associated with markedly increased IFN-gamma serum levels and up-regulation of major histocompatibility complex (MHC) class I and II expression in various epithelia. IL-12 induced a qualitatively similar macrophage infiltration in IFN-gamma R(-/-) mice, less marked splenomegaly (to 2 x normal), and no MHC upregulation. Strikingly increased vascular endothelial intercellular adhesion molecule-1 expression was apparent in both IFN-gamma R(-/-) and IFN-gamma R(+/+) mice. Restricted to mutant mice was a severe, invariably lethal, interstitial, and perivascular pulmonary macrophage infiltration with diffuse pulmonary edema. Extensive quantitative reverse transcriptase polymerase chain reaction analysis revealed an increase of only IL-6 and IL-10 pulmonary gene transcripts in IFN-gamma R(-/-) mice compared with wild-type mice. IL-12-induced myelosuppression is due to IFN-gamma-release from NK cells and T cells, and is associated with macrophage activation and distinct MHC class I and II antigen upregulation. The pulmonary pathology in IFN-gamma R(-/-) mice, however, reveals a toxic potential for IL-12 and suggests that endogenous IFN-gamma plays a protective role in preventing fatal pulmonary disease in these mice.

The stimulatory effects of interleukin (IL)-12 on hematopoiesis are antagonized by IL-12-induced interferon gamma in vivo

Michel Aguet

Interleukin (IL)-12 synergizes with other cytokines to stimulate the proliferation and differentiation of early hematopoietic progenitors in vitro. However, in vivo administration of IL-12 decreases peripheral blood counts and bone marrow hematopoiesis. Here, we used interferon (IFN) gamma receptor-deficient (IFN gamma R-/-) mice to investigate whether the in vivo inhibition of hematopoiesis by IL-12 is indirectly mediated by IL-12-induced IFN-gamma. IL-12 administered for 4 d (1 microgram/mouse per day) resulted in lower peripheral blood counts and a 2-fold decrease in bone marrow cellularity in wild-type mice, but not in IFN gamma R-/- mice. Bone marrow hematopoietic progenitors were decreased after IL-12 treatment in wild-type mice, but rather increased in IFN gamma R-/- mice. Splenic cellularity was 2.3-fold higher after IL-12 administration in wild-type mice, largely due to natural killer (NK) cell and macrophage infiltration together with some extramedullary hematopoiesis. In IFN gamma R-/- mice, spleen cellularity was less increased, there were fewer infiltrating NK cells, but a strong extramedullary hematopoiesis. Thus, alterations mediated by IL-12-induced IFN-gamma include reduction in bone marrow cellularity and hematopoietic progenitors, as well as pronounced splenomegaly, largely caused by NK cell infiltration. In the absence of IFN-gamma signaling, IL-12 promotes hematopoiesis, consistent with its in vitro activities.

1995

Genetic engineering of hematopoiesis for targeted IFN-α delivery inhibits breast cancer progression

Michele De Palma, Mario Leonardo Squadrito

The immunosuppressive tumor microenvironment represents a major hurdle to cancer therapy. We developed a gene transfer strategy into hematopoietic stem cells (HSCs) to target transgene expression to tumor-infiltrating monocytes/macrophages. Using a combination of transcriptional and microRNA-mediated control, we achieved selective expression of an interferon-α (IFN-α) transgene in differentiated monocytes of human hematochimeric mice. We show that IFN-α transgene expression does not impair engraftment and long-term multilineage repopulation of NSG (NOD/LtSz-scidIL2Rγ(null)) mice by transplanted human HSCs. By providing a source of human cytokines in the mice, we improved the functional reconstitution of human myeloid, natural killer, and T cell lineages, and achieved enhanced immune-mediated clearance of transplanted human breast tumors when hematopoiesis was engineered for tumor-targeted IFN-α expression. By applying our strategy to mouse breast cancer models, we achieved inhibition of tumor progression and experimental metastases in an autologous setting, likely through enhanced generation of effector T cells and their recruitment to the neoplastic tissues. By forcing IFN-α expression in tumor-infiltrating macrophages, we blunted their innate protumoral activity and reprogrammed the tumor microenvironment toward more effective dendritic cell activation and immune effector cell cytotoxicity. Overall, our studies validate the feasibility, safety, and therapeutic potential of a new cancer gene therapy strategy, and open the way to test this approach as adjuvant therapy in advanced breast cancer patients.

2014

Immune response in mice that lack the interferon-gamma receptor

Michel Aguet

Interferon-gamma (IFN-gamma) exerts pleiotropic effects, including antiviral activity, stimulation of macrophages and natural killer cells, and increased expression of major histocompatibility complex antigens. Mice without the IFN-gamma receptor had no overt anomalies, and their immune system appeared to develop normally. However, mutant mice had a defective natural resistance, they had increased susceptibility to infection by Listeria monocytogenes and vaccinia virus despite normal cytotoxic and T helper cell responses. Immunoglobulin isotype analysis revealed that IFN-gamma is necessary for a normal antigen-specific immunoglobulin G2a response. These mutant mice offer the possibility for the further elucidation of IFN-gamma-mediated functions by transgenic cell- or tissue-specific reconstitution of a functional receptor.

1993