Pulmonary dendritic cells

Dendritic cells (DCs) are leukocytes that are emerging as chief orchestrators of immune responses. The crucial task of DCs is the continuous surveillance of antigen-exposed sites throughout the body, and their unique responsibility is to decide whether to present sampled antigen in an immunogenic or tolerogenic way. Any misstep can either lead to a flawed immune defense or to allergy, even autoimmunity. It comes as no surprise that the lungs become increasingly the subject of DC-related investigations, as they represent a vast interface between the body and the outer world. This constitutes an enormous challenge for the immune system: "firing up" immune responses inappropriately could have devastating results for the fragile gas exchange structures. Evidence accumulates that DCs play a pivotal role in maintaining the delicate balance between tolerance and active immune response in our respiratory system. The exponentially growing body of DC-related publications is a big challenge. This article aims to provide researchers and clinicians with an up-to-date view on DC biology and its relevance to pulmonary medicine. A developing trend in the field of DCs is the shift from fundamental immunologic research toward exciting clinical insights and applications. For the pulmonary clinician, this heralds the dawn of promising therapies in various domains such as infections, allergy, and cancer.

Limited dose monoclonal IL-2R antibody induction protocol after primary kidney transplantation

This study prospectively compared immunoprophylaxis with a single intraoperative dose (2 mg/kg) of monoclonal interleukin-2 receptor (IL-2R) antibody vs. noninduction in kidney transplant recipients treated with tacrolimus (FK 506), mycophenolate mofetil (MMF) and a prednisone-based immunosuppression regimen. One hundred recipients of first-kidney transplant were enrolled into the study to receive either anti-IL-2R monoclonal antibody, daclizumab (2 mg/kg intraoperatively, limited anti-IL-2R) or no induction (control). Each patient also received oral tacrolimus (dosed to target trough level 10-15 ng/mL), MMF (500 mg bid) and prednisone. The primary efficacy end-point was the incidence of biopsy proven acute rejection during the first 6 months post-transplant. The patients were also followed for 12-month graft function, and graft and patient survival rates. Other than the donor's age being significantly lower in the control group, both groups were comparable with respect to age, weight, gender, race, human leukocyte antigen (HLA)-DR mismatch, panel reactive antibody (%PRA), cold ischemic time, cytomegalovirus (CMV) status, causes of renal failure, and duration and modes of renal replacement therapy (RRT). During the first 6 months, episodes of first biopsy confirmed acute rejection was 3/50 (6%) in the limited anti-IL-2R group and 8/50 (16%) in the controls (p < 0.05). Twelve-month patient 100/98 (%) and graft survival 100/96 (%) were not statistically different. The group receiving limited anti-IL-2R did not have any adverse reactions. Our study demonstrates that a limited (single) 2 mg/kg immunoprophylaxis dose with monoclonal IL-2R antibody (daclizumab) when combined with tacrolimus/MMF/steroid allows significant reduction in early renal allograft rejection to the single digit level. The therapy with anti-IL-2R antibody is simple and is well tolerated.

Antibodies directed at mouse IL-2-R alpha and beta chains act in synergy to abolish T-cell proliferation in vitro and delayed type hypersensitivity reaction in vivo

The anti-mouse IL-2-R beta chain mAb TM-beta 1 which, by itself, does not affect IL-2-dependent proliferation through the high affinity mouse IL-2 receptor, was shown to cooperate in a synergistic way with a set of anti-IL-2-R alpha chain mAbs both in vitro and in vivo. In vitro, when associated at equimolar concentrations, the TM-beta 1/anti-alpha mAb association was four to ten times more efficient at inhibiting the proliferation of the CTL-L2 cell line than was a similar concentration of anti-alpha mAb alone. In addition, a bispecific antibody in which a Fab' fragment of TM-beta 1 was covalently linked to a Fab' fragment of one of the anti-alpha mAb (5A2) was shown to be as efficient as the TM-beta 1/5A2 association. The association of TM-beta 1 with 5A2 was also tested in vivo in a sheep red blood cell-induced delayed type hypersensitivity (DTH) model. TM-beta 1 which, by itself, had no effect on DTH, induced a two- to threefold decrease in the doses of 5A2 required to suppress this cell-mediated immune reaction.

Monoclonal antibodies in renal transplantation: a review

OKT3 is the first anti-CD3 monoclonal antibody available for treatment in humans. Over the last few years it has proven to be a very powerful immunosuppressive agent in renal transplantation. Clinical studies have shown that OKT3 is superior to high-dose steroids as first-line treatment for acute renal allograft rejection. Furthermore, it is comparable to antithymocyte globulin (ATG) in treating steroid-resistant rejection and is also effective as rescue treatment in ATG- and antilymphocyte globulin-(ALG-) resistant rejection. Despite its excellent rejection-reversal rate, OKT3 treatment is followed by a substantial percentage of re-rejections, most of which respond well to steroids. In the early post-transplantation period, a prophylactic course of OKT3 is very effective in preventing acute rejections, and in this respect it is probably equivalent to ATG. Indirect evidence exists that a prophylactic course of OKT3 may be beneficial in immunologically high-risk patients and in patients with delayed graft function. However, more clinical studies are required to answer the question whether OKT3 should be given as induction treatment, as first-line treatment, or as rescue treatment. To answer this question, the side effects of OKT3 should also be taken into account. First-dose-related side effects, although frequent and disturbing, are usually transient and seldom life-threatening, provided overhydration has been corrected and steroids have been given before the first administration. These side effects are attributed to the release of cytokines as a result of T-cell activation or lysis. After exposure of patients to OKT3 an increased incidence of infections and malignancies has been reported. However, it is not yet clear whether this is due to OKT3 as such, or whether it merely reflects the total burden of immunosuppression. Xeno-sensitization represents an important limitation to OKT3 treatment, although a second or third course can still be effective in patients with low antibody titers. The precise immunosuppressive mechanism of anti-CD3 monoclonal antibodies is yet unknown. Monitoring of patients treated with OKT3 revealed CD3 and/or T-cell antigen receptor depletion and immunological incompetence of remaining T cells. More clinical data are required to establish the correct dose and duration of OKT3 treatment. In conclusion, OKT3 is a powerful immunosuppressive agent but its real value in renal transplantation remains to be determined. A practical approach may be to reserve it for the treatment of steroid-resistant rejections.(ABSTRACT TRUNCATED AT 400 WORDS)

Proliferation dependence and production of IL-2 in human alloreactive T-cell clones

Human alloreactive T-cell clones derived from cells invading a rejected kidney allograft were found to be capable of proliferating upon specific antigenic stimulation in short term assays and in the absence of exogenous IL-2. In most culture supernatants there was no evidence of any activity capable of triggering proliferation of the murine IL-2-sensitive CTL-L2 line. The ability of these clones to produce IL-2 was investigated under several experimental conditions. A combination of phorbol ester plus calcium ionophore was very efficient in all clones tested (17/17) in inducing transcription of the IL-2 gene. Conversely, when cell activation took place through the CD3/Ti complex, we regularly failed to detect hu-IL-2 transcripts even when the number of stimulator cells was increased. However, a blockade of IL-2-R with a monoclonal antibody inhibiting ligand receptor interaction while decreasing proliferation induced by the antigen in dose-dependent fashion permitted the presence of IL-2 to be demonstrated in supernatants. These results strongly suggest that IL-2-driven proliferation is essential in this model and may represent a major, although not exclusive, pathway leading to proliferation of these clones.