The immunostimulatory function of IL-12 in T-helper cell development and its regulation by TGF-beta, IFN-gamma and IL-4

Immunological findings in acute and chronic pancreatitis

BACKGROUND

In order to identify the role of mononuclear cells in pancreatitis, the immune picture at the cellular level has been studied. The cytokine production at the individual cell level in response to in vitro stimulation can help in identifying the percentage of specific cell types producing a particular cytokine.

METHODS

A total of 30 patients with acute pancreatitis (AP; n = 15) and chronic pancreatitis (CP; n = 15) were entered into the study and peripheral blood samples were drawn at the time of admission. A control group of 12 healthy individuals (age and sex matched) were also included in the study. Mononuclear cells from the peripheral blood from all three groups were separated on Ficoll gradient and labelled for surface antigens (i.e. cluster of differentiation (CD)3, CD4, CD8, CD25, CD14 and human leucocyte antigen D receptor (HLA-DR)) using monoclonal antibodies. The CD3+ and CD14+ cells were also stained for intracellular cytokines by specific monoclonal antibodies (i.e. for interferon (IFN)-gamma, interleukin (IL)-2, IL-4 & IL-10 in CD3+ cells and IL-6 and IL-12 in CD14+ cells). These fluorochrome-labelled cells were analysed on the flow cytometer.

RESULTS

The T-cell population is affected in pancreatitis where the CD4+ and CD8+ T-cell numbers are significantly altered. There is a marked reduction in CD4+ T cells in AP and CP. The CD8+ T cells were significantly reduced in AP. The IL-2 receptor is expressed in large numbers in AP and CP patient groups. The T cells from the CP group had a typical IL-2, IL-4 secreting pattern, while AP patients had a high IL-10, IFN-gamma and low IL-2, IL-4 population. The HLA-DR expression on monocytes differed significantly between the two groups, being strikingly reduced in chronic cases and significantly reduced in acute cases. The percentage of IL-6-producing monocytes was significantly higher in patients with AP as well as CP while IL-12 levels were higher in the CP than in the AP group.

CONCLUSIONS

T cells in CP are polarized towards the T-helper (Th)1 phenotype while the AP patients had a mixed population. This seems to be a part of immune deviation that is associated with development of CP and IL-12 appears to be instrumental in this process. The monocytes synthesize proinflammatory cytokines, which play an important role in the local and systemic consequences of the disease. In the disease clinical assessment such a study can provide useful information about the involvement of the immuno-inflammatory system.

IFN-gamma and IL-12 but not IL-10 are required for local tumour surveillance in a syngeneic model of orthotopic bladder cancer

In recent studies, a crucial role for IFN-gamma in immunosurveillance of tumours and in IL-12 immunotherapy has been suggested. Nevertheless, little is known about the relevance of IFN-gamma and IL-12 for tumour surveillance in noncytokine immunotherapy. Adjuvant immunotherapy with viable BCG (Bacillus Calmette--Guérin) is considered to be the most powerful clinical treatment regimen of bladder cancer and is known to induce a variety of proinflammatory cytokines. Consequently, we analysed the antitumour response of IFN-gamma knockout (KO), IL-12 KO and IL-10 KO mice in the absence and presence of BCG immunotherapy in a syngeneic orthotopic model of bladder cancer. IFN-gamma KO and IL-12 KO mice died much earlier and by far smaller tumour inocula compared to wildtype mice, while this intrinsic antitumour response was not altered in IL-10 KO mice. BCG immunotherapy was effective in wildtype mice, but totally ineffective in IFN-gamma KO and IL-12 KO mice. BCG induced a massive local immune response in the bladder of treated animals. This response was markedly increased in IL-10 KO mice, which coincides with increased therapeutic efficacy in this mouse strain compared with wildtype mice. Our data establish a crucial role for a Th1 type immune response in the intrinsic and immunotherapeutic control of local orthotopic bladder cancer.

Invasive candidiasis stimulates hepatocyte and monocyte production of active transforming growth factor beta

Candida albicans is an opportunistic fungal pathogen and a major cause of morbidity and mortality in patients with compromised immune function. The cytokine response to tissue invasion by C. albicans can influence the differentiation and function of lymphocytes and other mononuclear cells that are critical components of the host response. While the production of transforming growth factor beta (TGF-beta) has been documented in mice infected with C. albicans and is known to suppress phagocyte function, the cellular source and role of this cytokine in the pathogenesis of systemic candidiasis are not well understood. We have investigated the source of production of TGF-beta by immunohistochemical studies in tissue samples from patients with an uncommon complication of lymphoreticular malignancy, chronic disseminated candidiasis (CDC), and from a neutropenic-rabbit model of CDC. Liver biopsy specimens from patients with documented CDC demonstrated intense staining for extracellular matrix-associated TGF-beta1 within inflammatory granulomas, as well as staining for TGF-beta1 and TGF-beta3 within adjacent hepatocytes. These results correlate with the immunolocalization of TGF-beta observed in livers of infected neutropenic rabbits, using a neutralizing antibody that recognizes the mature TGF-beta protein. Human peripheral blood monocytes incubated with C. albicans in vitro release large amounts of biologically active TGF-beta1. The data demonstrate that local production of active TGF-betas by hepatocytes and by infected mononuclear cells is a component of the response to C. albicans infection that most probably contributes to disease progression in the immunocompromised host.

IL-12 prevents tolerance induction with mouse thyroglobulin by priming pathogenic T cells in experimental autoimmune thyroiditis: role of IFN-gamma and the costimulatory molecules CD40l and CD28

Deaggregated mouse thyroglobulin (dMTg) induces tolerance to experimental autoimmune thyroiditis (EAT), a Th1-cell-mediated disease. To test whether IL-12, a potent activator of Th1 cells, can overcome tolerance induction, different doses of IL-12 were given to CBA/J mice during the critical interval of 2--3 days after dMTg administration. After challenge with MTg/LPS, dMTg/IL-12-pretreated mice showed more extensive thyroiditis than immunized controls, but comparable levels of anti-MTg and T cell proliferation. Without challenge, few MTg antibodies were produced. In contrast, pretreatment with dMTg/poly A:U or dMTg/IL-1, two other T cell activators which also interfere with tolerance induction, induced antibodies before challenge, but not more severe thyroiditis. Mice pretreated with IL-12 without dMTg developed thyroiditis comparable to immunized controls, but less severe thyroiditis than dMTg/IL-12-pretreated mice. Clearly, IL-12 not only blocked tolerance induction, but also primed antigen-specific T cells during the tolerogenic period of dMTg pretreatment, resulting in stronger thyroiditis than immunization only. Neither treatment with anti-IFN-gamma nor the use of IFN-gamma knockout mice altered the capacity of IL-12 to prevent tolerance induction. However, both anti-CD28 and anti-CD40L antibodies diminished the priming effect by dMTg/IL-12. The mechanisms of IL-12 action include priming of MTg-specific T cells and the involvement of T cell costimulatory molecules.

Therapeutic Protective Effects of IL-12 Combined with Soluble IL-4 Receptor Against Established Infections of Herpes Simplex Virus Type 1 in Thermally Injured Mice

The effect of combination therapy between IL-12 and soluble IL-4R (sIL-4R) on the established infection of HSV-1 in thermally injured mice (TI mice) was investigated. All of the TI mice infected with lethal amounts of HSV-1 died when IL-12 was given therapeutically at a dose of 500 U/mouse. However, 80% of these mice treated prophylactically with IL-12 survived compared with 0% survival of the same mice treated with saline. The therapeutic administration of IL-12 to TI mice currently infected with HSV-1 caused an 80% survival of these mice when the treatment was combined with sIL-4R. Although IL-12 did not stimulate IFN-γ production in cultures of splenic T cells from TI mice, IFN-γ was produced by stimulation with IL-12 when the producer cells were prepared from TI mice that had been treated previously with sIL-4R. After stimulation with anti-CD3 mAb, splenic T cells from TI mice with the established infection of HSV-1 produced IL-4 into their culture fluids. However, IL-4 was not produced by splenic T cells that were prepared from the same infected mice treated with IL-12 and sIL-4R in combination. The results obtained herein indicate that the efficacies of the combination therapy against the established infection of HSV-1 may result from the IFN-γ production stimulated by IL-12 in TI mice that are treated with sIL-4R for reducing burn-associated type 2 T cell responses.