Reduced TGF-beta1 in patients with aplastic anaemia in vivo and in vitro

Transforming growth factor beta (TGF-beta) 1 is a ubiquitous bifunctional cytokine implicated in the regulation of haemopoietic stem cells and bone marrow stromal cells. We analysed sera from 63 patients with aplastic anaemia and describe a significant reduction of TGF-beta1 that was directly related to their treatment status. Untreated patients (n = 35), patients who did not respond (n = 15) and those with a partial response (n = 23) to treatment had significantly lower TGF-beta1 than the normal control group (n = 55), P < 0.0001, P < 0.0001 and P = 0.002 respectively. Patients in complete remission (n = 15) exhibited TGF-beta1 serum levels comparable to the control group. In addition, there was a correlation (r = 0.83, P < 0.0001) between serum TGF-beta1 and platelet count at time of sample. We have demonstrated that the primary source of TGF-beta1 in peripheral blood mononuclear cell (PBMC) cultures was not CD3-positive cells. These data indicate aplastic anaemia is associated with a decreased TGF-beta1 expression in peripheral blood circulation, which may be a direct consequence of thrombocytopenia. In vitro stromal layers grown from aplastic patient bone marrow (n = 14) produced significantly lower levels of TGF-beta1 (P = 0.02) when compared to normal stroma (n = 15). In the aplastic anaemia bone marrow compartment we postulate that accessory cells down-regulate TGF-beta1 expression to allow stem cell cycling to counteract hypoplasia. As TGF-beta1 is important in the regulation of haemopoiesis, dysregulation of this cytokine in combination with previously described abnormal cytokine expression may contribute significantly to the pathophysiology of aplastic anaemia by exacerbating primary stem cell defects.

Bioassays for the characterisation and control of therapeutic cytokines; determination of potency

The primary value of bioassays is that they alone directly assess the biological activity of bioactive substances and products like cytokines. Appropriately designed bioassays reflect the fundamental aspects of the biological activity of a cytokine molecule, including ligand-receptor binding, signal transduction processes (often poorly understood) and the final observed biological effects. Biological assays therefore complement physicochemical and biochemical procedures which normally only assess precise molecular structural features of cytokines. Bioassays provide valuable information concerning the potency of cytokine products. This is essential for evaluating batch-to-batch consistency, appropriate formulations and stability. Bioassay data are crucial at all stages in the development of cytokine products, from early research to final quality control of finished product. However, the type and design of bioassays may differ according to the information required and its intended use. The assays may or may not directly relate to the clinical use of the product. Bioassays can be difficult to perform and time consuming, although this often reflects bad assay choice and/or design. Correct analysis of the assay results is essential if valid data are to be obtained. Standardisation, using correctly calibrated primary and secondary standards, is essential. In vivo bioassays are normally more unreliable than in vitro procedures, but in some cases in vitro systems are either not available or do not address important biological characteristics of a product. Bioassays must be validated for their intended purpose and for the types of samples to be measured. Appropriate statistical analysis should be used to derive the significance and specifications of results. This needs to address both variability in samples and assay performance. Specifications (limits) for product acceptability need to be derived from real data using several batches of cytokine product.

Spontaneously occurring neutralizing antibodies against granulocyte-macrophage colony-stimulating factor in patients with autoimmune disease

There is increasing evidence that spontaneous anticytokine autoantibodies are associated with chronic infections and autoimmune diseases. We report the sporadic occurrence in autoimmune diseases of such autoantibodies to granulocyte-macrophage colony-stimulating factor (GM-CSF), a cytokine involved in inflammation and the regulation of proliferation, differentiation and function of granulocytic and monocytic cell lineages. In 41 of 425 patients tested, we found low to moderate levels of autoantibodies binding to GM-CSF in serum or plasma. These were most prevalent in patients with myasthenia gravis (MG). However, neutralizing autoantibodies against GM-CSF were very rare, being found in only three patients. Two had autoimmune MG, one with thymoma (Patient A) and the other (Patient B) with 'seronegative' MG, i.e. without the antiacetylcholine receptor autoantibodies characteristic of most MG patients, and a third (Patient D) had multiple sclerosis. Only very limited amounts of Patient A and Patient D serum/plasma were available for analysis and therefore further studies were carried out on the more plentiful samples from Patient B. The anti-GM-CSF autoantibodies of Patient B were predominantly polyclonal immunoglobulin G and strongly neutralized recombinant human (rh) GM-CSF derived from different expression systems. They had similar immunological and immunochemical characteristics to anti-GM-CSF antibodies that developed in immunocompetent colorectal carcinoma patients following (rh)GM-CSF therapy. In serial samples from Patient B, the anti-GM-CSF autoantibodies were undetectable from diagnosis at age 8 years until at least age 13, but then developed spontaneously during (temporary) withdrawal of immunosuppressive treatment. Their neutralizing activity has persisted since their first detection at age 15 years 1 month, and was at its highest level recently at age 17 years 7 months. There was no obvious association with other autoimmune phenomena, nor were any haematological deficiencies overtly manifested, suggesting that any loss of GM-CSF function may have been compensated for by other cytokines.

Immunogenicity of granulocyte-macrophage colony-stimulating factor (GM-CSF) products in patients undergoing combination therapy with GM-CSF

In this study, we have assessed the development of neutralizing and nonneutralizing granulocyte-macrophage colony-stimulating factor (GM-CSF) antibodies in two groups of patients with metastatic colorectal carcinoma receiving two different GM-CSF products. Three clinical trials were carried out, and a combination of GM-CSF and a colon carcinoma-reactive antibody was used in the absence of any concomitant chemotherapy. Two different GM-CSF products, both rDNA-derived and produced in Escherichia coli, were used. Patients in Trial 1 received product X, and those in Trials 2 and 3 received product Y. Patients in Trial 2 also received interleukin 2 in an attempt to potentiate immune responses. After the first cycle of treatment, no GM-CSF antibodies were detected, but on subsequent therapy, 28 of the 38 patients tested receiving product Y (Trials 2 and 3) developed antibodies that bound to the GM-CSF product used for therapy. However, none of the patients developed antibodies that neutralized the biological activity of GM-CSF, as assessed using an in vitro bioassay. Furthermore, there was no in vivo impairment in GM-CSF-induced expansion of leukocytes, neutrophils, and eosinophils in the patients. In contrast, 19 of the 20 patients given product X (Trial 1) developed GM-CSF binding antibodies, and 9 of these patients were shown to develop antibodies that neutralized the biological activity of GM-CSF. The presence of the latter was associated with a significant reduction in GM-CSF-induced expansion of leukocytes, neutrophils, and eosinophils in patients. Therefore, product X appears to be more immunogenic than product Y. Immunochemical characterization confirmed that the specificity of the antibody responses varied depending on the product used for therapy. Whereas sera from Trial 1 patients treated with product X showed the presence of antibodies with strong recognition of GM-CSF proteins, sera from patients treated with product Y showed varied recognition of GM-CSF ranging from fairly strong to very weak but bound predominantly to two E. coli-derived, non-GM-CSF-related proteins of Mr approximately 20,000 and Mr approximately 30,000. Therefore, in sera from patients receiving product Y, the antibody specificity appeared to be directed not only against GM-CSF but also against non-product-related host cell contaminants. This study shows that GM-CSF products used for therapy are potentially immunogenic and generate antibodies to GM-CSF and/or other non-product-related contaminants. However, only antibodies that neutralize the biological activity of GM-CSF compromise therapeutic efficacy of the cytokine.

Persistence of Atrial Fibrillation After Its Induction-Importance of the Duration and Dispersion of Atrial Refractoriness and Electrical Remodeling

BACKGROUND: The electrophysiologic mechanisms of the persistence of atrial fibrillation (AF) after its initiation are not well understood. Therefore, the electrophysiologic characteristics of the right atrium were evaluated in an acute, pacing-induced model of AF in the pig in order to identify parameters associated with persistence of AF. METHODS AND RESULTS: AF was induced by rapid atrial pacing in 30 anesthetized, open-chest, juvenile pigs. Sustained (S) AF was defined as that lasting >10 minutes, nonsustained (NS) AF <10 minutes but >30 seconds, and no (N) AF <30 seconds. Activation mapping and programmed stimulation (S1S1 = 200 ms) was performed at 56 electrodes on the right atrial free wall, to determine ERP (mean and minimum), dispersion of refractoriness (ERPdisp, ELEdisp), conduction velocity (CV), wavelength, AF cycle length (mean of 10 beats), and AF cycle length/time (electrical remodeling). SAF was induced in 10 pigs, NSAF in 9, and NAF in 11. AF cycle length was shorter in SAF and/vs NS vs NAF (P <.001). Mean ERP (107 +/- 9 and/vs 122 +/- 5 vs 142 +/- 9, p <.001) and wavelength (7 +/- 1 and/vs 9 +/- 1 vs 11 +/- 1, P <.001) were shorter in SAF and/vs NSAF vs NAF. Minimum ERP was shorter in SAF and NSAF vs NAF (P <.001). CV at cycle lengths of 200 and 150 msec was not different between groups. Dispersion of ERP was greater in SAF and/vs NSAF vs NAF (8 +/- 1 and/vs 11 +/- 1 vs 19 +/- 4, P <.001). CONCLUSIONS: Persistence of AF correlated with shorter ERP and wavelength, and greater dispersion of ERP and electrical remodeling. There was no correlation with CV.

Inherited interleukin 12 deficiency in a child with bacille Calmette-Guérin and Salmonella enteritidis disseminated infection

Interferon-gamma receptor ligand-binding chain (IFN-gammaR1) or signaling chain (IFN-gammaR2) deficiency, like interleukin 12 receptor beta1 chain (IL-12Rbeta1) deficiency, predispose to severe infections due to poorly virulent mycobacteria and salmonella. A child with bacille Calmette-Guérin and Salmonella enteritidis infection was investigated. Mutations in the genes for IFN-gammaR1, IFN-gammaR2, IL-12Rbeta1, and other molecules implicated in IL-12- or IFN-gamma-mediated immunity were sought. A large homozygous deletion within the IL-12 p40 subunit gene was found, precluding expression of functional IL-12 p70 cytokine by activated dendritic cells and phagocytes. As a result, IFN-gamma production by lymphocytes was markedly impaired. This is the first discovered human disease resulting from a cytokine gene defect. It suggests that IL-12 is essential to and appears specific for protective immunity to intracellular bacteria such as mycobacteria and salmonella.

Cytokine immunoassays: recommendations for standardisation, calibration and validation

Accurate and sensitive methods for measurement and detection of cytokines are important for the understanding of cytokine biology and biochemistry and the assessment of cytokine involvement in pathology and physiological processes. Various types of assays are available for estimation of cytokine levels in biological fluids. Often, immunoassays are used for this purpose but in many cases inappropriate assay choice, design and standardisation have led to confusing or erroneous data and conclusions. Only if well characterized, validated and standardized methods are used and results carefully analysed can useful unambiguous information be obtained. This article contributes significantly towards the standardisation, calibration and validation aspects of immunoassays for cytokines.

The use of bioassays for the characterisation and control of biological therapeutic products produced by biotechnology

The primary value of bioassays is that they alone directly assess biological activity of bioactive substances and products. Appropriately designed bioassays reflect the fundamental aspects of the biological activity of a bioactive molecule, including ligand-receptor binding, signal transduction processes (often poorly understood) and the final observed biological effects. Biological assays therefore complement physicochemical and biochemical procedures which normally only assess precise molecular structural features of complex molecules produced by biotechnology. Bioassays provide valuable information concerning the potency of biological products. This is essential for evaluating batch-to-batch consistency and stability. Bioassay data are crucial at all stages in the development of biological products, from early research work to final quality control of finished products. However, the type and design of bioassays may differ according to the information required and its intended use. The assays may or may not directly relate to the clinical use of the product. Bioassays can be difficult to perform and be time consuming, although this often reflects bad assay choice and/or design. Correct analysis of the assay results is essential if valid data are to be obtained. Standardisation, using correctly calibrated primary and secondary standards, is essential. In vivo bioassays are normally more unreliable than in vitro procedures, but in some cases the latter are either not available or do not address important biological characteristics of a product. Bioassays must be validated for their intended purpose and for the types of samples to be measured. Appropriate statistical analysis should be used to derive the significance and specifications of results. This needs to address both variability in samples and assay performance. Specifications (limits) for product acceptability need to be derived from real data using several batches of product.

Are cytokines in platelet concentrates responsible for febrile transfusion reactions?

In recent years, several studies have identified the leukocyte content and the age of the blood components as dominant factors in febrile transfusion reactions (FTRs). At present, extensive efforts are being made to reduce adverse effects by implementation and/or introduction of new methods for leuko-depletion of blood components and by studying the mechanisms responsible for these phenomena. A recent approach has been the evaluation of cytokines in platelet concentrates and this issue has been addressed with some detail in this review. Comparative data currently available on levels of cytokines in the different platelet concentrates is provided along with the functional role of the detected cytokines in including adverse reactions.

Production and characterization of monoclonal antibodies to human interleukin-12

Interleukin-12 is a cytokine that plays a central role in mediating cell mediated immunity via enhancement of a TH1 cell response. IL-12, unusually for a cytokine, has a heterodimeric structure made up of 35 kDa and 40 kDa subunits. The aim of this study was to produce and characterize monoclonal antibodies to recombinant human IL-12. Twenty-two monoclonal antibodies to IL-12 were successfully produced and subunit specificity determined using recombinant human IL-12 and chimeric murine/human IL-12. All antibodies were shown to react with the p40 subunit by ELISA and immunoblotting with three of the MAbs being found to cross-react with murine IL-12. Using two individual bioassays for IL-12, seven of the MAbs were shown to neutralize biological activity of IL-12. Ten of the antibodies were found to be of use in immunocytochemistry, reacting with LPS-stimulated peripheral blood monocytes. The approaches and difficulties encountered in characterizing antibodies to a heterodimeric cytokine are discussed together with possible reasons for the failure to generate antibodies to the p35 subunit.

Cytokines in platelet concentrates: a comparison of apheresis platelet (haemonetics) and filtered and unfiltered pooled buffy-coat derived platelet concentrates

Variable degrees of platelet activation, shape changes, microvesiculation and fragmentation may occur during collection, processing and storage of platelet concentrates (PCs), contributing to different rate of platelet storage lesion. Leukocytes contribute to both the frequency of transfusion reactions and the acceleration of the rate of platelet storage lesion hence leukocyte removal of platelet concentrates has been introduced to overcome these problems. However transfusion reaction can still occur with the use of leuko-reduced products and it is not fully elucidated that the rate of storage lesion is equivalent for filtered and unfiltered counter parts. This issue has been addressed in this manuscript comparing the generation of cytokines during storage in PCs derived from pooled buffy coat with the standard apheresis products, with a similar level of leukocyte contamination. The EDTA-induced shape change in platelet was used as an index of platelet functional integrity. In addition IL-8 and TGF beta were used as indicators of filtration process-inducing stimulation of cytokines. Our results clearly indicate that a rapid disc/spheric conversion occurs during storage of buffy-coat derived PC, and while prestorage filtration reduces both IL-8 content immediately after filtration and at the end of platelet shelf life but such a process may lead to slight enhancement of the rate of TGF beta generation indicating that any additional process may have some bearing in stimulation of TGF beta release.

Treatment of metastatic renal cell carcinoma with subcutaneous interleukin 2: evidence for non-renal clearance of cytokines

The circulating cytokine concentrations following administration of subcutaneous recombinant interleukin 2 (IL-2) in combination with interferon alpha and 5-fluorouracil used to treat advanced renal cancer were studied. One patient was anephric and on dialysis, and seven had normal biochemical renal function, although five had undergone single nephrectomy. The pharmacokinetics of IL-2 and changes in IL-6 and tumour necrosis factor (TNF)-alpha were essentially similar in all patients including the anephric patient, irrespective of the periods of dialysis, although at some time points, IL-2 concentrations were slightly higher in the anephric patient than in the others. These results show that for subcutaneous administration of low-dose IL-2, renal clearance of IL-2 is not important. This contrasts with high-dose, intravenous IL-2 where blood concentrations are higher and renal clearance seems to occur, perhaps because of saturation of the non-renal mechanisms of clearance. The subcutaneous route is certainly preferred if IL-2 is used in anephric patients and in those with impaired renal function, and it may be generally preferred for most purposes.

IL-4 and TNF-alpha-mediated proliferation of the human megakaryocytic line M-O7E is regulated by induced autocrine production of GM-CSF

In this study, the authors examined the effects of recombinant human interleukin 4 (rhIL-4) and recombinant human tumour necrosis factor alpha (rhTNF-alpha) alone or in combination on proliferation of the human cytokine dependent myeloid cell line, M-O7e. While rhIL-4 or rhTNF-alpha alone induced only a weak proliferative response, a synergistic proliferative signal was clearly evident on stimulation of cells with a combination of both cytokines. The stimulatory effect of rhTNF-alpha is mediated predominantly by the 55-kDa TNF receptor because the agonistic monoclonal antibody htr-9 and the Trp32 Thr86 TNF-alpha mutant protein specific for this receptor type produced similar results to rhTNF-alpha. In contrast, the Asn143 Arg145 TNF-alpha mutant protein specific for the 75-kDa TNF receptor produced only minimal proliferation of M-O7e cells. Using RT-PCR, we found that rhTNF-alpha rapidly and strongly induced granulocyte-macrophage colony-stimulating factor (GM-CSF) mRNA production, while rhIL-4 was a slow and less efficient inducer of GM-CSF mRNA. However, there was little evidence of the TNF-alpha/IL-4 combination acting synergistically on GM-CSF mRNA production as the levels of GM-CSF mRNA increased only marginally compared with IL-4 or TNF-alpha alone. Thus, the observed synergistic effect of TNF-alpha/IL-4 costimulation of M-O7e cells seems to be mediated via induction of GM-CSF secretion rather than an enhanced production of GM-CSF mRNA. Higher levels of GM-CSF were detectable in supernatants of cells treated with both rhIL-4 and rhTNF-alpha than in cells stimulated with either cytokine alone. Furthermore, addition of a neutralising antibody against GM-CSF abrogated the observed synergistic effect of rhIL-4 and rhTNF-alpha treatment, indicating that the rhIL-4/TNF-alpha combination acts to significantly increase GM-CSF release which then acts in an autocrine manner to enhance the proliferation of M-O7e cells.

Neutralising antibodies to granulocyte-macrophage colony stimulating factor (GM-CSF) in carcinoma patients following GM-CSF combination therapy

There is a high risk of developing neutralizing and non-neutralizing antibodies when GM-CSF is used as an immunomodulatory agent in non-immune compromised patients and not in combination with chemotherapy. The presence of neutralizing antibodies may seriously hamper the clinical response of the patients this must be taken into account when designing protocols if the biological activity of the exogenously administered GM-CSF is not to be impaired and the endogenous production of GM-CSF is not to be inactivated. Assessment of production of neutralising antibodies during cytokine therapy is important for predicting the clinical response to progressive therapy.

Production of neutralizing granulocyte-macrophage colony-stimulating factor (GM-CSF) antibodies in carcinoma patients following GM-CSF combination therapy

In this study, the development of neutralizing and non-neutralizing GM-CSF antibodies and the clinical consequences related to the induction of these antibodies were analysed in 20 patients with metastatic colorectal carcinoma receiving a combination therapy of Escherichia coli-derived GM-CSF and a colon carcinoma-reactive MoAb in the absence of any concomitant chemotherapy. The recombinant human GM-CSF was administered subcutaneously for 10 days every month for 4 months. Following the first cycle of treatment, no GM-CSF antibodies were detected, but during subsequent therapy, 19 of the 20 patients studied developed GM-CSF binding antibodies. However, only a proportion (40%) of the 19 antibody-positive patients developed antibodies that neutralized the biological activity of GM-CSF in an in vitro bioassay. The presence of GM-CSF neutralizing antibodies was associated with a significant reduction in GM-CSF-induced expansion of leucocytes, neutrophils and eosinophils. Such clinical effects were not apparent in patients with non-neutralizing antibodies. Further characterization of sera from patients with neutralizing antibodies showed that, in most cases, the antibodies neutralized the biological activity of GM-CSF preparations derived using different expression systems (Chinese hamster ovary cells and yeast), suggesting that these antibodies may have the potential to cross-react with endogenously produced GM-CSF. These effects should be considered before therapeutic use of cytokines, particularly in patients who are not immunosuppressed, and therefore capable of mounting an effective immune response. Our results indicate that assessment of production of neutralizing antibodies induced during cytokine therapy can be used to predict diminished clinical response to further therapy.

Cytokine levels in platelet concentrates: quantitation by bioassays and immunoassays

Some adverse reactions to the transfusion of platelet concentrates (PCs) cannot be attributed to antibodies against blood cells or to subclinical microbial agents. It has been suggested that leucocyte-derived inflammatory cytokines such as interleukin (IL)-1, IL-6 and tumour necrosis factor (TNF) may contribute to a larger number of unexplained non-antibody-mediated adverse reactions. Three types of PCs, containing different levels of leucocytes, are currently produced. Filtration is used on demand to further reduce leucocyte contamination of these components. we have monitored the plasma of PCs prepared by the platelet-rich plasma method (PRP), the buffy-coat method or by apheresis for IL-6, IL-1, transforming growth factor-beta (TGF-beta), TNF and interferon gamma (IFN gamma). Biologically active IL-6 increased in stored PRP-PCs from a mean of 140 pg/ml on day 1 to 2395 pg/ml on day 5/6. Elevated levels of IL-8, as detected by immunoassay, were evident in PRP-PCs during routine storage under blood bank conditions. Small amounts of immunoreactive IL-1 with only minimal biological activity were present in some PRP-PCs by day 5/6. No significant increase in the levels of IL-8, IL-6 or IL-1 were seen in buffy-coat PCs during storage for 5/6 d. For apheresis PCs, an increase in IL-8 content, but not in IL-6 over 6 d was observed. In all three types of PCs, elevated amounts of both bioactive and immunoreactive TGF beta were present, but there was no evidence of any biologically active or immunoreactive TNF alpha. Pre-storage filtration of PRP-PCs for depletion of leucocytes prevented the increase in IL-8 and IL-6 levels of these PCs. Our results show that leucocyte reduction by buffy-coat method reduces cytokine levels to a comparable level to filtered or apheresis PCs, containing low levels of leucocytes, but use of these PCs in minimizing the severity and incidence of reactions in recipients will require clinical evaluation. This is the first comprehensive and comparative study which, on the basis of biological activity of cytokines, directly indicates that the mode of platelet production grossly influences the levels of cytokines.

Evidence for a signaling role for the alpha chains of granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3), and IL-5 receptors: divergent signaling pathways between GM-CSF/IL-3 and IL-5

In the present study, we have used a human erythroleukemia cell line, TF-1, that proliferates in response to granulocyte macrophage colony stimulating factor (GM-CSF), interleukin-3 (IL-3), and interleukin-5 (IL-5) to investigate the role of receptors for these cytokines in signal transduction mechanisms involved in proliferative responses. The receptors for GM-CSF, IL-3, and IL-5 each possess a cytokine specific alpha subunit, but all three share a common beta chain. Using an immunoblotting system designed to detect phosphotyrosine containing proteins and a permeabilized cell system to detect rapid changes in phosphate turnover on proteins, we show that while GM-CSF and IL-3 use tyrosine phosphorylation to mediate mitogenic signal transduction, IL-5 uses tyrosine dephosphorylation in its signaling pathway. The use of different signaling pathways by these cytokines can be confirmed in a biologic system whereby the proliferation induced in culture by GM-CSF and IL-3 is inhibited by tyrosine kinase inhibitors, but that induced by IL-5 is enhanced. Conversely, GM-CSF- and IL-3-induced proliferation is stimulated by a tyrosine phosphatase inhibitor, yet IL-5-induced proliferation is inhibited. Inhibitors of protein kinase C inhibit IL-3- and GM-CSF-, but not IL-5-induced proliferation. We suggest that, because all these cytokines share the identical beta chain of their receptors, the cytokine specific alpha chain mediates the linkage of each receptor to the individual biochemical signal transduction pathways responsible for the different biologic activities of these cytokines.

Association of changes in monocyte antigen presentation and cytokine production in haemophilic boys with treatment and blood-borne virus infection

Aspects of monocyte function (antigen presentation and cytokine production (e.g. IL-1, IL-6) have been studied in a normal control population and three groups of haemophilic boys: group 1 HIV and HCV seronegative and treated only with a single heat-treated factor VIII (FVIII) concentrate; group 2 HIV seronegative but HCV seropositive; group 3 all HIV and HCV seropositive. Groups 2 and 3 have been previously treated with unheated and heated FVIII concentrate. Group 1 boys (HIV/HCV uninfected) showed no significant reduction in monocyte antigen presentation function nor IL-1 or IL-6 production when compared with a control population. Group 2 boys (HCV infected) showed a reduced monocyte antigen presentation activity (P < 0.05), but no significant reduction in IL-1 or IL-6 production. Group 3 boys (HIV and HCV infected) showed a significantly reduced monocyte antigen presentation activity (P < 0.001) and an impairment of IL-1 and IL-6 production (P < 0.05). A significant reduction of IL-1 and IL-6 production was only seen in the HIV and HCV infected haemophilic boys, implicating HIV as an aetiological agent. In contrast, reduced monocyte antigen presentation activity was seen in haemophilic boys with both HIV and HCV infection or HCV alone. The HIV and HCV seronegative boys had normal antigen presentation. The absence of immune modulation in haemophilic boys that have not acquired HIV and HCV infection suggests that chronic blood-borne virus infections as contributory to immune modulation seen in haemophiliacs with virus infections.

Factor VIII concentrates and the immune system--laboratory investigations

Evidence suggests that haemophiliacs treated with factor VIII concentrates show abnormalities in immune functions. The basis of this is not clear, but some factor VIII concentrates down-regulate Fc receptors on monocytes which may explain the impaired function of these cells. Some concentrates inhibit lymphocyte proliferation and interleukin-2 secretion by human T-cell lines and peripheral blood lymphocytes. They can also inhibit activity of other cytokines such as interleukin-4 and interleukin-5 and secretion of cytokines such as interleukin-1 and granulocyte macrophage colony stimulating factor. These effects are product-related and vary from total inhibition to virtually no detectable inhibition. Of particular significance is that the degree of inhibition is not related to the purity or gross protein composition of the products. The inhibitory activity is not due to factor VIII itself as antibody affinity purified factor VIII products are entirely non-inhibitory. The main inhibitory protein components appear to be of approximately 200 kDa and 60 kDa (by gel filtration). Recent evidence suggests that transforming growth factor-beta (TGF-beta), derived from the plasma used for fractionation, is a major contaminant of 'inhibitory' concentrates and is responsible for the effects, observed in vitro, of concentrates on cytokine secretion or activity. The levels of TGF-beta varied between products and correlated with inhibition of interleukin-2 secretion from stimulated T-cells. The presence of TGF-beta in concentrates may therefore explain the immunosuppression observed in recipients of these products. Correlation of the inhibitory effects with clinically important consequences such as increased susceptibility to infections or decreased CD4 counts also remains to be established.