The immunoregulatory effects of NK cells: the role of TGF-beta and implications for autoimmunity

Autoimmunity and malaria: what are they doing together?

A common feature of autoimmunity is the presence of autoantibodies (AAb). Two types of AAb have been described: the 'pathogenic' AAb, associated with autoimmune diseases (AID), and the so-called 'natural' AAb. The latter are present in all normal individuals and have been postulated to play a major role as a first defensive barrier of the organism. Both the 'pathogenic' and the 'natural' AAb can be detected at higher frequencies among individuals exposed to viral, bacterial and parasitic infections. The malaria associated AAb do not seem to result from a generalised polyclonal B-cell activation (PBA), have specificities that may differ according to the degree of clinical immunity and do not seem to be pathogenic. Malaria may offer a protective effect against AID, by diminishing its severity or by either preventing or retarding its expression. AAb could also participate in the immune protection against malaria, and this could happen in several ways: (i) AAb directed to modified Ag expressed on the red blood cell (RBC) membrane during parasitisation and (ii) AAb reactive with crypto- or neo-Ag revealed on both normal and infected RBC membranes, by destroying infected, and also normal, erythrocytes; (iii) anti-idiotype AAb specific of the binding site of anti-merozoite Ab, which would mimic the parasite ligand for the RBC receptor, by competing with parasites and blocking RBC invasion; (iv) AAb cross-reactive with parasite material - such as nuclear or cytoskeleton Ag - having a direct parasiticide activity; (v) the natural AAb network, through its 'anti-bacterial first defense barrier'; and finally (vi) anti-phospholipid (PL) AAb, by neutralizing the pathogenic properties of parasite-derived PL. Finally, in view of currently available knowledge, it is concluded that, since AAb are not always pathogenic, the price for an 'autoimmunity-mediated' protection in malaria would not necessarily be immunopathology and clinical autoimmunity, and a protective role of AAb could be exerted with no danger to the host.

Lipopolysaccharide stimulates the proliferation of human CD56+CD3- NK cells: a regulatory role of monocytes and IL-10

NK cells recognize and kill tumor cells and normal cells, and these play an important role in immune defense in cancer, infectious disease, and autoimmunity. NK killing is regulated by positive or negative signals derived from the interaction of surface receptors with ligands on the target cells. However, the mechanisms controlling the proliferation and maintenance of NK cells in normal human individuals are less clearly defined. In this study, using an entirely autologous system, we demonstrate that human peripheral blood CD3-CD56+, killer cell-inhibitory receptor (KIR)-expressing cells proliferate and expand in response to LPS. These responses are enhanced in the presence of anti-IL-10 receptor-blocking Abs or on the removal of CD14+ cells from the cultures. This enhancement is also reflected in substantial increases in cytolytic activity and IFN-gamma production. The negative effect of CD14+ cells may also be IL-10 mediated, IL-10 being lost from the culture supernatants of CD14-depleted PBMC and rIL-10 reversing the effect of this depletion. On the other hand, mRNA for the p35 and p40 subunits of IL-12 is still induced in CD14-depleted cultures. The expansion of CD3-CD56+ cells was also inhibited by CTLA4-Ig, indicating a role for CD80/86. B lymphocytes were not required for the expansion of CD3-CD56+ cells, whereas removal of MHC class II+ cells from CD14-depleted cultures resulted in a complete abrogation of these responses. Expansion of CD3-CD56+ cells was reconstituted in MHC class II-depleted cell cultures by adding back monocyte-derived dendritic cells. These results indicate that the responses of CD3-CD56+ NK cells to LPS may be driven by a MHC class II+ B7+ CD14- peripheral population, most likely blood dendritic cells.

Clusterin may be involved in rat liver allograft tolerance

Little is known about the possible role of complement inhibitors on tolerance induced by liver allografts. Clusterin, which is a plasma glycoprotein, inhibits cytolytic membrane attack complex (MAC) of complement by binding to soluble C5b-7 complex. The role of clusterin in relation to the naturally achieved tolerance in a rat orthotopic liver transplantation (OLT) has not been investigated before. Here we determined the kinetics of clusterin expression at different post-transplantation time points in a tolerogenic model (DA-PVG) where rejection was naturally overcome without any immunosuppressive drugs in comparison with the syngenic OLT model (DA-DA). Peripheral blood and liver tissues were taken from OLT at various post-operative time points. A strong expression of soluble clusterin was observed on post-transplantation day 7, which occurred at the peak of the rejection in this tolerogenic OLT model. The expression of clusterin remained strong even after tolerance was achieved. The intensity of clusterin expression was much stronger when compared with the syngenic OLT (DA-DA) model after OLT. A strong expression of clusterin mRNA was also observed in the tolerogenic model on post-OLT day (POD) 7 and the expression persisted when compared with the syngenic model on post-OLT day 60. Our data have shown that the strongest levels of clusterin during the reaction phase in tolerogenic OLT may be involved in tolerance induction.

Effects of short-term JP-8 jet fuel exposure on cell-mediated immunity

The U.S. Air Force has implemented the widespread use of JP-8 jet fuel in its operations, although a thorough understanding of its potential effects upon exposed personnel is unclear. Exposure to environmental toxicants such as JP-8 may have significant effects on host physiology. Jet fuel exposure has been shown to cause human liver dysfunction, abnormal electroencephalograms, shortened attention spans, and decreased sensorimotor speed. Previous studies have shown that short-term, low-concentration JP-8 exposure had significant effects on the immune system; e.g., decreased viable immune cell numbers, decreased immune organ weights, and loss of immune function that persisted for extended periods of time (i.e., up to 4 weeks post-exposure). In the current study, an in-depth analysis of the effects of JP-8 exposure on cellular immunity was performed. Short-term (7 days, 1 h/day), low-concentration (1000 mg/m3) exposures were conducted in mice, and T cell and natural killer (NK) cell functions were analyzed 24 h after the last exposure. The exposure regimen was found to almost completely ablate NK cell function, as well as significantly suppress the generation of lymphokine-activated killer (LAK) cell activity. Furthermore, JP-8 exposure suppressed the generation of cytotoxic T lymphocyte (CTL) cells from precursor T cells, and inhibited helper T cell activity. These findings demonstrate that JP-8 jet fuel exposure has significant detrimental effects on immune functions of exposed individuals. JP-8 jet fuel should be considered a potential and significant immunotoxicant. Chronic exposure to JP-8 may have serious implications to the long-term health of exposed individuals.

Targeting of Human Dendritic Cells by Autologous NK Cells

NK cells have the capacity to spontaneously kill tumor cell lines, in particular cell lines of hemopoietic origin. In contrast, they do not generally kill nontransformed autologous cells. However, here we demonstrate that short-term activated polyclonal human NK cells, as well as human NK cell lines, efficiently lyse autologous dendritic cells (DC) derived from peripheral blood monocytes as well as Langerhans-like cells derived from CD34+ stem cells isolated from umbilical cord blood. Lysis of autologous DC by short-term activated NK cells and NK cell lines was dependent on granule exocytosis, since total abrogation of lysis was observed in the presence of EGTA. Induction of DC maturation by LPS, monocyte conditioned media (MCM), or stimulation through CD40 ligand (CD40L) rendered the DC less susceptible to lysis by NK cells. Infection of DC with influenza virus was likewise associated with a reduced susceptibility to lysis by NK cells. Thus, susceptibility to lysis by autologous NK cells is a particular property of immature DC. The present results are discussed in relation to the ability of DC to interact with NK cells and to the ability of NK cells to regulate development of specific immunity.

Role of NK cells and TGF-beta in the regulation of T-cell-dependent antibody production in health and autoimmune disease

Natural killer (NK) cells are a third lymphocyte population especially important in innate immunity. NK cells may also have an important role in the regulation of acquired immunity. These lymphocytes spontaneously produce large amounts of both active and latent transforming growth factor-beta (TGF-beta). NK-cell-derived TGF-beta1 enabled activated CD8(+) T cells to inhibit antibody production by blocking the induction of this response. Production of lymphocyte-derived TGF-beta is decreased in systemic lupus erythematosus. Insufficient levels of this cytokine in SLE and other autoimmune diseases may contribute to defective T regulatory cell function characteristic of this and other autoimmune diseases. NK cells are found in mucosal tissues and the TGF-beta spontaneously released by these cells could contribute to the usual tolerogenic response of T cells to antigens presented at these sites. Thus, in addition to its well known immunosuppressive effects, TGF-beta could have an equally important role in the generation of regulatory T cells.

Synergistic proliferation and activation of natural killer cells by interleukin 12 and interleukin 18

We investigated the effects of IL-12 and IL-18 on unstimulated murine splenocytes and observed that the two cytokines strongly synergized for their proliferation, whereas IL-12 and IL-18 alone were essentially inactive in this respect. Phenotypical and functional analyses of cells proliferating in response to IL-12 and IL-18 revealed that large granular Ly-49C(+)DX5(+)CD3(-)NK blasts were expanded in these cultures and that they displayed cytotoxic activity against Yac-1 cells, a murine NK cell target. Further analyses indicated three major differences between NK cells appearing in response to IL-12 and IL-18 and those derived in the presence of other NK cell growth factors, such as IL-2 or IL-15. First, a population of T-NK cells, i.e. expressing T cell (TCRalphabeta, CD3) and NK cell (Ly-49) markers, was detected amongst cells growing in IL-2 or IL-15 but not in cultures supplemented with IL-12 and IL-18. Second, most NK cells derived with IL-2 or IL-15 expressed the NK1.1 antigen, while those derived with IL-12 and IL-18 did not. Finally, striking differences were observed regarding cytokine production. Cells stimulated with IL-12 and IL-18 in combination, but not with IL-2 or IL-15, produced IFN-gamma, IL-3, IL-6 and TNF. IFN-gamma was not involved in the response of NK cells to IL-12 and IL-18, as indicated by experiments demonstrating that the combination of the two cytokines displayed similar effects on spleen cells from IFN-gammaR-knock-out mice. Receptor (IL-12Rbeta1, IL-12Rbeta2 and IL-18R) gene expression studies did not indicate that the mechanism underlying the synergy between IL-12 and IL-18 involved reciprocal induction of their receptors. Taken together, our results demonstrate that IL-12 and IL-18 exert striking synergistic activities for NK cell proliferation and activation, distinct from those induced by IL-2 or IL-15.

Signaling Through CD43 Induces Natural Killer Cell Activation, Chemokine Release, and PYK-2 Activation

Natural killer (NK) cell activation is the result of a balance between positive and negative signals triggered by specific membrane receptors. We report here the activation of NK cells induced through the transmembrane glycoprotein CD43 (leukosialin, sialophorin). Engagement of CD43 by specific antibodies stimulated the secretion of the chemokines RANTES, macrophage inflammatory protein (MIP)-1, and MIP-1β, which was prevented by treatment of cells with the specific tyrosine kinase inhibitor genistein. Furthermore, signaling through CD43 increased the cytotoxic activity of NK cells and stimulated an increase in the tyrosine kinase activity in antiphosphotyrosine immune complexes of NK cell lysates. PYK-2 was identified among the tyrosine kinase proteins that become activated. Hence, PYK-2 activation was observed after 20 minutes of CD43 stimulation, reached a maximum after 45 to 60 minutes, and decreased to almost basal levels after 120 minutes of treatment. Together, these results demonstrate the role of CD43 as an activation molecule able to transduce positive activation signals in NK cells, including the regulation of chemokine synthesis, killing activity, and tyrosine kinase activation.

Chronic allograft rejection. Do the Th2 cells preferentially induced by indirect alloantigen recognition play a dominant role?

Chronic rejection has been the major obstacle to the long-term allograft survival in the clinic. Although the etiology of this rejection reaction is multifactorial, alloantigen-specific immune activation plays the most critical role. We herein hypothesize that CD4+ Th2 cells that are preferentially induced by the indirect recognition of allogeneic histocompatibility antigens late in transplantation may play the most critical role in the initiation and/or maintenance of chronic allograft rejection. Immunosuppression used to prevent acute rejection and the nature of antigen-presenting cells and alloligands in the graft may all contribute to immune deviation to the Th2 response. This response may be further perpetuated by type 2 cytokines conceivably produced by activated macrophages, NK cells, and CD8+ T cells in the graft. Cytokines and growth factors induced by this type 2 response, in turn, allow for activation of B, endothelial, and smooth muscle cells that collectively contribute to the pathogenesis of chronic allograft rejection by producing alloantibodies and growth hormones required for interstitial fibrosis, extracellular matrix deposition, and vascular neointimal hyperplasia.

Activation of infiltrating cytotoxic T lymphocytes and lymphoma cell apoptotic rates in gastric MALT lymphomas. Differences between high-grade and low-grade cases

In this study, we have characterized infiltrating T lymphocytes from 13 low-grade and 17 high-grade primary gastric MALT lymphomas by immunohistochemistry, with particular regard to the presence, activation, and topographic distribution of cytotoxic effectors. Although the prevalence of CD4+ and CD8+ cells was similar in low- and high-grade lymphomas, higher numbers of TIA-1+ cytotoxic effectors were found in this latter group of cases (11.6 versus 7. 8%; P = 0.004). Activation of CD8+ cytotoxic T lymphocytes (CTLs) was significantly more pronounced in high- than in low-grade lymphomas, as shown by immunostaining for perforin (8.7 versus 4.0%; P = 0.001) and granzyme-B (GrB) (8.7% versus 3.0%; P < 0.0001). Of note, CD20/GrB double labeling showed that high-grade lymphomas carried a markedly higher content (about ninefold) of activated CTLs relative to the number of CD20+ lymphoma B cells (0.081 +/- 0.076 versus 0.009 +/- 0.011; P < 0.0001). Moreover, high-grade lymphomas showed significantly increased apoptotic rates compared to low-grade cases (5.3 and 1.1% of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL)-positive cells, respectively; P < 0.0001). In the whole series, the percentage of GrB+ cells and the GrB+/CD20+ ratio showed a strong linear correlation with the number of TUNEL-labeled cells. These findings, together with the frequent colocalization of CTLs and TUNEL+ neoplastic cells, suggested that apoptotic death of lymphoma cells may be due at least in part to the killing by cytotoxic effectors. Our results are consistent with the occurrence of host antitumor cell-mediated immune responses in gastric MALT lymphomas. Moreover, the finding of stronger cytotoxic responses in high- than in low-grade cases is of potential usefulness in the design of more effective therapeutic strategies for the management of these disorders.

Abundance of NKT cells in the salivary glands but absence thereof in the liver and thymus of aly/aly mice with Sjögren syndrome

It is known that ALY/Nsc Jcl-aly/aly (aly/aly) mice that congenitally lack lymph nodes fall victim to Sjögren syndrome as a function of age. We investigated how TCRint cells of extrathymic origin and TCRhigh cells of thymic origin are distributed in various organs of these mice. Although the distribution of T-cell subsets was not different between control aly/+ and aly/aly mice in youth in any of the tested organs, the proportion of TCRint cells in the liver and spleen of aly/aly mice increased with aging. Usually, TCRint cells in the liver comprise a half-and-half mixture of a NK1. 1(+) subset (i.e., NKT cells) and a NK1.1(-) subset. In constrast, almost all expanding TCRint cells in various immune organs of aly/aly mice were found to be NK1.1(-). A large proportion of lymphocytes, including NK cells and TCRint cells, were also present in the salivary glands of aly/aly mice. Interestingly, these TCRint cells in the salivary glands contained an NK1.1(+) subset (i.e., NKT cells) that used an invariant chain of Valpha14Jalpha281 for TCRalphabeta (>50%). Moreover, gammadeltaT cells that used Vgamma 1, 2, 4/Vdelta 1, 4, 6 mRNAs, different from those of gammadeltaT cells in the liver and intestine, were abundant. Possibly reflecting the in situ generation of these T cells in the salivary glands, the expression of RAG-2 mRNA was evident by the RT-RCR method. These results suggest that (i) inflammatory lymphocytes that evoke Sjögren syndrome in aly/aly mice are NK cells or TCRint cells (both NK1.1(+) and NK1.1(-) subsets) and (ii) TCRint cells in the salivary glands might be generated in situ.

Targeted disruption of SMAD3 results in impaired mucosal immunity and diminished T cell responsiveness to TGF-beta

SMAD3 is one of the intracellular mediators that transduces signals from transforming growth factor-beta (TGF-beta) and activin receptors. We show that SMAD3 mutant mice generated by gene targeting die between 1 and 8 months due to a primary defect in immune function. Symptomatic mice exhibit thymic involution, enlarged lymph nodes, and formation of bacterial abscesses adjacent to mucosal surfaces. Mutant T cells exhibit an activated phenotype in vivo, and are not inhibited by TGF-beta1 in vitro. Mutant neutrophils are also impaired in their chemotactic response toward TGF-beta. Chronic intestinal inflammation is infrequently associated with colonic adenocarcinoma in mice older than 6 months of age. These data suggest that SMAD3 has an important role in TGF-beta-mediated regulation of T cell activation and mucosal immunity, and that the loss of these functions is responsible for chronic infection and the lethality of Smad3-null mice.

Role of HLA in congenital heart block: susceptibility alleles in mothers

In congenital heart block (CHB), abnormal maternal immunisation leads to autoantibody production against SS-A/Ro and SS-B/La antigens. These maternal antibodies are transferred across the placenta to the unborn child and are believed to transmit irreversible immunological injury in developing foetal heart tissue, thus causing 3rd-degree atrioventricular block. The mothers may suffer from systemic lupus erythematosus (SLE) or primary Sjögren's syndrome (SS), but they may be asymptomatic. Women with primary SS show a typical autoimmune HLA antigen pattern, namely higher frequency of HLA B8 and DR3 than in the normal population. The HLA pattern may affect individual ability to resist infecting bacteria and viruses and to response in various ways to autoantigens. It is probable that other factors such as genetic regulation of immune response are involved in CHB. We compared the HLA class I and class II alleles of mothers having CHB children with those of women suffering from primary SS and having healthy children, and with those of healthy Finns. Antibodies against 52-kD and 60-kD SS-A/Ro and 48-kD SS-B/La antigens were compared between the two groups of mothers. Our results show that anti-SS-A/Ro antibody-positive mothers all show a strong association with known autoimmune-predisposing HLA alleles, however, the mothers of CHB children differ in some HLA class I alleles, and especially in HLA haplotypes, from mothers of healthy children. Mothers with HLA A1, Cw7, B8 and without B15 are at particularly high-risk of having CHB children.

CD48-deficient mice have a pronounced defect in CD4(+) T cell activation

We have generated mice deficient in the expression of the lymphocyte cell surface antigen CD48 (Blast-1, BCM1, sgp-60) by gene targeting in embryonic stem cells. Mice homozygous for the CD48 mutation (CD48(-/-) mice) are severely impaired in CD4(+) T cell activation. Proliferative responses to mitogens, anti-CD3 mAb, and alloantigen are all reduced. Experiments in which T cells and antigen-presenting cells from either wild-type or CD48(-/-) mice were cocultured reveal that CD48 is important on both T cells and antigen-presenting cells. The most dramatic impairment was observed in experiments in which highly purified T cells were stimulated through the T cell receptor in the presence of the phorbol ester, phorbol 12-myristate 13-acetate. The results of these experiments raise the possibility that CD48 plays a role in signaling through the T cell receptor.

Predominant expression of T helper 2 cytokines and altered expression of T helper 1 cytokines in long-term allograft survival induced by intrathymic immune modulation with donor class I major histocompatibility complex peptides

BACKGROUND

We have recently demonstrated that three synthetic peptides corresponding to the alpha-helices of the alpha1 and alpha2 domains of the donor class I RT1.Aa molecule served as efficient CD4+ T-cell epitopes for indirect recognition of this molecule during cardiac allograft rejection in the PVG.R8-toPVG.1U rat strain combination. These peptides induce long-term graft survival when injected into the thymus 7 days before transplantation under the cover of transient immunosuppression with anti-rat lymphocyte serum. In this study, we analyzed intragraft cytokine gene expression to test whether immune deviation to the T helper (Th) 2 response is associated with long-term allograft survival in this model.

METHODS

Intragraft cytokine gene expression was analyzed using a competitive reverse transcription polymerase chain reaction method we developed for this study. Cytokine gene expression was quantified in control allografts (n=5) with acute rejection and allografts from intrathymically manipulated recipients with acute rejection (n=5), delayed rejection (n=7), or no rejection (n=8).

RESULTS

Long-surviving allografts expressed high levels of interleukin (IL)-4, IL-10, transforming growth factor (TGF)-beta, interferon (IFN)-gamma, and undetectable levels of IL-2. Allografts that were rejected in a delayed fashion expressed mostly IL-2, IFN-gamma, and TGF-beta with low or undetectable levels of IL-4 and IL-10. Acutely rejected allografts from unmanipulated controls or peptide-manipulated recipients expressed high levels of IL-2, IFN-gamma, TGF-beta and undetectable levels of IL-4 or IL-10. All allografts also expressed T-cell receptor Cbeta gene, providing evidence for the presence of T-cell infiltrates in the grafts.

CONCLUSIONS

These observations demonstrate that acute graft rejection in this model is associated with the expression of Th1 cytokines, IL-2, and IFN-gamma, whereas long-term survival is associated with predominant expression of Th2 cytokines, IL-4, and IL-10. The expression of IFN-gamma in long-surviving allografts in the absence of IL-2 provides evidence for altered activation of the Th1 response in this intrathymic immune modulation model.

Cutting Edge: Identification of the 2B4 Molecule as a Counter-Receptor for CD48

The CD48 molecule belongs to a subfamily of the Ig superfamily that also includes the CD2, CD58, 2B4, Signaling lymphocyte activation molecule (SLAM), and Ly-9 molecules. Receptor-ligand interactions are known to occur between several members of this family, and these interactions can strengthen cell to cell adhesion. In mice, the CD48 molecule can bind to CD2. To search for additional ligands of murine CD48, we have generated a chimeric fusion protein consisting of the extracellular domain of murine CD48 and the C region of human IgG1. The results of immunofluorescence and immunoprecipitation experiments in which this reagent was used identify the 2B4 molecule as a novel counter-receptor of CD48.

Phenotyping of peripheral blood lymphocytes in adult coeliac disease

In coeliac disease immunological abnormalities are not confined to the small bowel and it has been suggested that changes in peripheral blood lymphocytes may predispose to autoimmune or malignant complications. Using dual-colour immunofluorescence with labelled monoclonal antibodies, multiparameter flow cytometry was used to analyse peripheral blood lymphocytes in 32 untreated coeliacs, 29 treated coeliacs and 20 healthy volunteers. When the absolute numbers were considered, a decrease of CD3+, CD4+, CD8+ and CD19+ lymphocytes was found in untreated coeliacs compared with treated coeliacs and healthy volunteers. The proportion of CD3+ was significantly higher in untreated coeliacs (P<0.05) than in healthy volunteers. No differences were observed in CD4+, CD8+ and CD19+ subsets between the three groups studied. The proportion of CD3+ CD25+ and CD3+ HLA-DR+ cells were higher in untreated coeliacs (P<0. 001 and P>0.005) and in treated coeliacs (P<0.005 and P<0.05) than in healthy volunteers. On the contrary, natural killer cells and cytotoxic cells were lower in untreated and treated coeliacs than in healthy volunteers. As regards B-cell subsets, the only difference was the increase in FcepsilonR+ B cells in untreated coeliacs. The absolute reduction of peripheral lymphocytes in coeliac disease probably reflects their compartimentalization in intestinal mucosa. The decrease of natural killer cells and cytotoxic cells may be in keeping with the increased prevalence of malignancy in this condition. Finally, the phenotypic changes found in untreated coeliacs indicate T-cell activation.

Interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha) are necessary in the early stages of induction of CD4 and CD8 cytotoxic T cells by Mycobacterium leprae heat shock protein (hsp) 65 kD

Cytotoxic T cells (CTL) may play an important role in host defence against mycobacterial infections. CD4 CTL are preferentially induced by mycobacteria, but both CD4 and CD8 CTL may be necessary components of a protective immune response. The 65-kD mycobacterium heat shock protein (hsp65) is a poor inducer of CTL in multibacillary leprosy (MB) patients. In this study we evaluate the possible role of cytokines in modulating the cytotoxic activity of CTL from leprosy patients and normal individuals (N) against autologous macrophages presenting Mycobacterium leprae hsp65. Our results show that hsp65-specific CTL were generated from both CD4 and CD8 lymphocytes. In N, individual cytokines as well as the combination of them were able to modify the hsp65-induced cytotoxic activity. The effect of cytokines on leprosy patients' lymphocytes was different in MB and paucibacillary (PB) patients. Thus, IL-6, IL-2, IFN-gamma or TNF-alpha did not modify the generation of hsp65-CTL from either MB (with or without an erythema nodosum episode (ENL)) or PB. In all the patients the simultaneous addition of two cytokines was required in order to increase CTL generation. In MB, IL-6 plus IFN-gamma or IL-2 increased both CD4 and CD8 CTL, while TNF-alpha plus IFN-gamma up-regulated only CD4 CTL. In PB, CD8 CTL were prominent with IL-6 plus IFN-gamma, while the increase was significant in CD4 CTL with IL-6 plus IL-2. Down-regulation of CTL was observed by addition of IL-4, IL-10, anti-IFN-gamma or anti-TNF-alpha in N controls. Our data demonstrate that IFN-gamma and TNF-alpha must be present for at least the first 60 h of the induction stage in order to generate full hsp65 CTL. Hence, IFN-gamma and TNF-alpha would be key factors in the generation of hsp65 CTL.

Inhibitory cytokines in asthma

Although research in asthma has concentrated on complex proinflammatory mechanisms, it is likely that defective expression of cytokines that inhibit allergic inflammation, such as interleukin 10, interleukin 12 and interferon gamma, might also be important, particularly in determining disease severity and persistence of inflammation in the airways. Therapy based on these cytokines might also be useful, with the advantage that it restores the balance of endogenous cytokines. We discuss the therapeutic potential of these and other inhibitory cytokines in the treatment of asthma, particularly in patients with severe disease that is poorly responsive to conventional therapy, or as a disease-modifying treatment when used early.

Decreased production of interleukin-12 and other Th1-type cytokines in patients with recent-onset systemic lupus erythematosus

OBJECTIVE

To determine the profile of Th1-type and Th2-type cytokines produced by mononuclear cells from patients with recent-onset systemic lupus erythematosus (SLE), prior to the initiation of treatment with corticosteroids.

METHODS

Using sensitive radioimmunoassays, interleukin-4 (IL-4), IL-10, IL-12 p40, tumor necrosis factor alpha (TNF alpha), interferon-gamma (IFN gamma), and granulocyte-macrophage colony-stimulating factor (GM-CSF) released into the culture supernatants of various unstimulated and stimulated blood mononuclear cell populations from 10 SLE patients was assessed in comparison with 10 matched healthy controls studied in parallel.

RESULTS

In early SLE, monocyte-enriched cells constitutively produced increased amounts of IL-10 and decreased amounts of IL-12 following stimulation. Lymphocyte-enriched cells in SLE produced decreased amounts of IFN gamma and TNF alpha following stimulation. In "rested" cells, these defects were accentuated and a defect in IL-12 production was suggested. Depletion studies suggested that CD8+ cells were a major source of TNF alpha and IFN gamma in controls, but not in SLE patients. Increased IL-4 production or abnormalities in GM-CSF production were not observed.

CONCLUSION

This study suggests that even early in the course of SLE, monocyte production of IL-10 is increased and that of IL-12 is decreased. Decreased production of Th1-type cytokines in SLE may be secondary to this imbalance between IL-10 and IL-12. A contributory role of dysfunctional CD8+ cells is suggested.