Conventional protein kinase C plays a critical role in negative regulation of CD98-induced homotypic aggregation

CD98, a heterodimeric type II transmembrane protein, is involved in many different cellular events, ranging from amino acid transport to cell-cell adhesion. Little is known about the positive and negative signalling pathways involved in these responses. Therefore, we examined the role of conventional protein kinase C (PKC) isoforms during CD98-induced intracellular signalling and homotypic aggregation of U937 cells. The CD98-induced aggregation was enhanced by the general protein kinase inhibitors GF109203X and staurosporin, and by specific PKC-alpha/-beta peptide inhibitor 19-27, but inhibited by PKC activators such as phorbol 12-myristate 13-acetate (PMA). PMA-inhibition was reversed by PKC inhibitors recognising the ATP-binding site in PKC (e.g. staurosporin, GF109203X and Go6983). Inhibitors which bind to diacylglycerol (DAG) or Ca(2+)-binding sites of PKC (calphostin C and Go6967) had no effect. PMA-induced translocation of conventional PKC (cPKC) isozymes (alpha, beta and gamma), but decreased the expression of PKC-delta, which plays an important role in CD98-induced homotypic aggregation. PMA treatment also suppressed the surface level of CD98 but not CD29, CD18 and CD147, dose- and time-dependently. These data provide evidence that PMA-responsive cPKC isoforms (alpha, beta and gamma) play a key role in negative regulation of CD98 signalling and homotypic aggregation.

Autocrine type I interferon amplifies dendritic cell responses to lipopolysaccharide via the nuclear factor-kappaB/p38 pathways

The central role of dendritic cells (DC) in the initiation of immune responses requires these cells to be able to determine the degree of danger in their microenvironment. Abrogating the activity of type I interferon (IFN) secreted after lipopolysaccharide (LPS) stimulation of DC inhibits CD86 and human leucocyte antigen-DR (HLA-DR) upregulation at a low LPS concentration. At a higher concentration of LPS, while changes in surface phenotype are not dependent on type I IFN, this cytokine is required for maximal secretion of interleukin-12 (IL-12) and tumour necrosis factor-alpha (TNFalpha) by DC. Thus, the secretion and autocrine activity of type I IFN after Toll-like receptor stimulation enables DC to orchestrate a hierarchical maturation response with regard to changes in surface phenotype and secretion of cytokines. In addition, the activation of nuclear factor-kappaB and p38 pathways in DC can occur either in an additive fashion when DC are exposed to dual stimulation or can be activated in discrete phases over time when DC are exposed to LPS alone. The differential activation of these pathways provides a mechanism for DC to integrate the activation by multiple stimuli and thus amplify responses to pathogen infection.

The interaction between staphylococcal superantigen-like proteins and human dendritic cells

Staphylococcus aureus produce a family of exotoxins (staphylococcal superantigen like proteins, SSLs) with structural, but not functional, homology to superantigens. These proteins have previously been shown to interact selectively with antigen presenting cells, including dendritic cells. The functional consequences of this interaction are now explored. SSL7 and 9 had no effect on viability or morphology of dendritic cells. The proteins did not induce dendritic cell maturation, as measured by cell surface phenotype. Exposure to SSL did not alter the ability of dendritic cells to take up FITC-dextran. Finally, exposure to SSLs did not impair the ability of the dendritic cells to stimulate allogeneic or antigen specific T cell responses. However, dendritic cells loaded with SSL7 or 9 were able to stimulate a T cell proliferative response in 3/8 healthy individuals tested. Sera from nine out of 10 individuals tested contained antibodies against both SSL7 and SSL9, and the response to each SSL was specific and not cross-reactive. The results demonstrate that SSLs are immunogenic in humans at both the B and T cell level, but it remains unclear whether this response is to the benefit of the bacterium or the host.

Autologous apoptotic T cells interact with dendritic cells, but do not affect their surface phenotype or their ability to induce recall immune responses

Dendritic cells (DCs) play an important role in determining immunogenicity and the subsequent immune response. They may also have a role in maintaining peripheral tolerance to self-antigens by initiating an immune response only in the context of danger signals released from cells during stress, damage or death. These signals may originate from surrounding T cells as well as from other cells. Therefore, in this study the effect of autologous T cell injury on DC morphology and function has been investigated. Co-incubation of apoptotic or necrotic T cells with immature DCs altered their morphology towards a more mature appearance, with more cells showing activation as judged by spreading and formation of arborizing long processes. The apoptotic autologous T cells were rarely phagocytosed by immature DCs, compared to macrophages. The DC surface phenotype was not affected by the co-incubation with autologous injured T cells. The ability of DCs to elicit a secondary immune response was not altered by exposure to autologous injured T cells. These findings suggest that DC can continue to function in T cell activation, rather than in tolerogenic mode, even in the presence of large numbers of dying autologous T cells, such as may be present in the aftermath of an acute antiviral response.

Effect of taurine chloramine, the product of activated neutrophils, on the development of collagen-induced arthritis in DBA 1/J mice

Taurine chloramine (TauCl), a product of neutrophil myeloperoxidase - halide system, formed by a reaction of taurine with HOCl, is known as an anti-microbial and anti-inflammatory long-lived oxidant. We previously reported that TauCl inhibits in vitro the production of proinflammatory cytokines (IL-6, IL-8) by RA synoviocytes. Therefore we performed this study to investigate the effect of TauCl treatment on the development of collagen-induced arthritis (CIA) in DBA1/J mice. Early administration of TauCl (after primary immunization) resulted in the delay of the onset of CIA, but had no effect on severity of arthritis. TauCl, given daily for 21 days after booster immunization, did not reduce the symptoms of arthritis in those mice, which already developed CIA, but significantly diminished incidence of the disease (55% vs. 90% of placebo mice). The mechanism of this effect is unknown. This is the first in vivo study suggesting that TauCl may be used for immune intervention in chronic inflammatory diseases.

Placentally derived prostaglandin E2 acts via the EP4 receptor to inhibit IL-2-dependent proliferation of CTLL-2 T cells

A number of immunomodulatory molecules are present in the placenta, including cytokines, prostaglandins, progesterone and indoleamine 2,3-dioxygenase. An undefined factor capable of down-regulating T-cell activity has recently been reported [1] as being produced by short-term cultures of placental fragments. By careful repetition of these studies we have confirmed that chorionic villi isolated from term placenta produce a low molecular weight, heat stable factor capable of inhibiting the IL-2-dependent proliferation of mouse CTLL-2 cells. This activity was not due, however, to a previously unknown immunosuppressive molecule, but rather to prostaglandin E2 (PGE2). Expression of cyclooxygenase (COX)-2 was detected in the syncytiotrophoblast of chorionic villi explants using immunohistochemistry. Culture of the explants in the presence of the COX-1/COX--2 inhibitors indomethacin and diclofenac, or with the COX-2-selective inhibitor DFP, blocked the production of the immunosuppressive factor. The immunosuppressive activity was restored by adding PGE2 to the supernatants obtained from diclofenac-inhibited explants. A number of different receptors are involved in mediating the biological effects of prostaglandins. By utilizing selective antagonists of individual receptors, we have established that the immunosuppressive effect of PGE2 on CTLL-2 cells is exerted via the EP4 receptor. Thus, addition of an EP4-selective antagonist, but not of EP1 or EP3 antagonists, abolished the immunosuppressive effect of PGE2 on CTLL-2 cells. This may have implications for attempts to selectively manipulate T-cell responses.

Regulation of primary HIV-1 isolate replication in dendritic cells

The potential role of dendritic cells (DC) in the immunopathology of human immunodeficiency virus 1 (HIV-1) disease remains controversial. This study examines replication of a panel of HIV-1 strains (both laboratory adapted and primary) within DC, in the context of the well-established monocyte-DC and monocyte-macrophage transition. Viral replication was assessed by p24 ELISA assay. All strains of HIV-1 tested replicated in DC. Only CCR5-tropic virus replicated in macrophages. Lipopolysaccharide (LPS) induced DC maturation (as reflected in altered cell phenotype) and at the same time diminished the ability of DC to support HIV-1 replication. In contrast the presence of activated T cells, which had been fixed to prevent them acting as a site for viral replication, enhanced the ability of the DC to support viral replication, as has been reported previously for macrophages. Thus cells that are DC by phenotype, but are not activated, act as the optimum reservoir for HIV-1 replication. If this form of DC is present in peripheral tissues, this will be permissive for amplification of the in vivo viral load at sites where there are few responder cells available, and hence contribute to the persistent immunopathology.

Dendritic cell activation and cytokine production induced by group B Neisseria meningitidis: interleukin-12 production depends on lipopolysaccharide expression in intact bacteria

Interactions between dendritic cells (DCs) and microbial pathogens are fundamental to the generation of innate and adaptive immune responses. Upon stimulation with bacteria or bacterial components such as lipopolysaccharide (LPS), immature DCs undergo a maturation process that involves expression of costimulatory molecules, HLA molecules, and cytokines and chemokines, thus providing critical signals for lymphocyte development and differentiation. In this study, we investigated the response of in vitro-generated human DCs to a serogroup B strain of Neisseria meningitidis compared to an isogenic mutant lpxA strain totally deficient in LPS and purified LPS from the same strain. We show that the parent strain, lpxA mutant, and meningococcal LPS all induce DC maturation as measured by increased surface expression of costimulatory molecules and HLA class I and II molecules. Both the parent and lpxA strains induced production of tumor necrosis factor alpha (TNF-alpha), interleukin-1alpha (IL-1alpha), and IL-6 in DCs, although the parent was the more potent stimulus. In contrast, high-level IL-12 production was only seen with the parent strain. Compared to intact bacteria, purified LPS was a very poor inducer of IL-1alpha, IL-6, and TNF-alpha production and induced no detectable IL-12. Addition of exogenous LPS to the lpxA strain only partially restored cytokine production and did not restore IL-12 production. These data show that non-LPS components of N. meningitidis induce DC maturation, but that LPS in the context of the intact bacterium is required for high-level cytokine production, especially that of IL-12. These findings may be useful in assessing components of N. meningitidis as potential vaccine candidates.

Immunomodulation using bacterial enterotoxins

Immunologic unresponsiveness (tolerance) is a key feature of the mucosal immune system, and deliberate vaccination by a mucosal route can effectively induce immune suppression. However, some bacterial-derived proteins, e.g. cholera toxin and the heat labile toxin of Escherichia coli, are immunogenic and immunomodulatory at mucosal surfaces and can effectively adjuvant immune responses to codelivered bystander antigens. This review summarizes some of the structural and biological characteristics of these toxins and provides examples of how these properties have been exploited for tolerance induction and mucosal vaccine development.

A defect in bone marrow derived dendritic cell maturation in the nonobesediabetic mouse

The pathogenesis of diabetes in the nonobese diabetic (NOD) mouse is characterized by a selective destruction of the insulin-producing beta-cells in the islets of Langerhans mediated by autoreactive T cells. The function of T cells is controlled by dendritic cells (DC), which are not only the most potent activators of naïve T cells, but also contribute significantly to the establishment of central and peripheral tolerance. In this study, we demonstrate that the NOD mouse (H2: K(d), Ag(7), E*, D(b)) shows selective phenotypic and functional abnormalities in DC derived from bone marrow progeny cells in response to GM-CSF (DC(NOD)). NOD DC, in contrast to CBA DC, have very low levels of intracellular I-A molecules and cell surface expression of MHC class II, CD80, CD86 and CD40 but normal beta 2-microglobulin expression. Incubation with the strong inflammatory stimulus of LPS and IFN-gamma does not increase class II MHC, CD80 or CD86, but upregulates the level of CD40. The genetic defect observed in the DC(NOD) does not map to the MHC, because the DC from the MHC congenic NOD.H2(h4) mouse (H2: K(k), A(k), E(k), D(k)) shares the cell surface phenotype of the DC(NOD). DC from these NOD.H2(h4) also fail to present HEL or the appropriate HEL-peptide to an antigen-specific T cell hybridoma. However all the DC irrespective of origin were able to produce TNF-alpha, IL-6, low levels of IL-12(p70) and NO in response to LPS plus IFN-gamma. A gene or genes specific to the NOD strain, but outside the MHC region, therefore must regulate the differentiation of DC in response to GM-CSF. This defect may contribute to the complex genetic aetiology of the multifactorial autoimmune phenotype of the NOD strain.

Early commitment of adoptively transferred CD4+ T cells following particle-mediated DNA vaccination: implications for the study of immunomodulation

The early responses of CD4+ T cells to particle-mediated DNA immunisation were investigated using OVA-specific TCR-transgenic CD4+ T cells. Following adoptive transfer of these cells, mice were immunised by delivery into the skin of a plasmid encoding ovalbumin. Transgenic T cells underwent a rapid and transient antigen-specific activation, followed by clonal expansion (up to approximately 6% of total lymphocytes). Immunisation with ovalbumin in CFA evoked similar responses with slightly faster kinetics. Numerous antigen-specific T cells synthesising IFN-gamma (Th1) and IL-4 (Th2) were detectable using both intracellular staining and ELISPOT assays. This study provides a quantitative analysis of both T cell proliferation and Th1/Th2 balance following particle-mediated DNA immunisation and establishes a robust and sensitive model in which to assess modulation of helper T cell responses in DNA vaccination.

Inhibition of T-cell response by Escherichia coli heat-labile enterotoxin-treated epithelial cells

Escherichia coli heat-labile enterotoxin (LT) is an extensively studied adjuvant of mucosal responses. Nevertheless, its mode of action as an adjuvant remains incompletely understood. In this study, we describe a simplified in vitro model with which to look at some aspects of immunoregulation by LT. The interaction of LT with the apical surface of a monolayer of CaCo-2 epithelial cells induces the release of a soluble factor which inhibits the antigen-induced release of interleukin-2 by T cells cultured at the basolateral side of the cells. The release of this factor requires the ADP-ribosylating activity of LT since the isolated B subunit, as well as an enzymatically silent LT mutant, loses biological activity in this model. The inhibitory activity is likely to be due to prostaglandin release, since it is blocked by indomethacin. The contribution of LT-induced prostaglandin release to the complex immunoregulatory activity of LT is discussed.

Novel molecular mechanisms of dendritic cell-induced T cell activation

In this study we have re-examined the molecular mechanisms involved in activation of T cells by dendritic cells (DC). Human peripheral blood DC (PBDC) were derived by 2 h adhesion followed by 7 day culture in a combination of granulocyte macrophage colony stimulating factor and IL-4, and depletion of residual T and B cells. These PBDC were used to induce autologous T cell proliferation in a CD3-dependent response, and antibodies against CD11a/18 and CD86 were used as control inhibitors of accessory function. Antibodies against five of the cell surface molecules that we have recently identified on the surface of DC, CD13, CD87, CD98, CD147 and CD148, and an antibody which recognizes a molecule that has not as yet been identified, all inhibited the CD3-induced T cell proliferation. These findings were observed not only when antibodies were present throughout the culture, but also when they were prepulsed on to the surface of the DC, suggesting the inhibition was mediated via the antigen-presenting cells rather than the T cell. The same set of antibodies also inhibited an allospecific mixed lymphocyte reaction, confirming that the inhibitory effect was not dependent on the use of a CD3 antibody as the stimulating agent. All the antibodies of known specificity inhibited both CD4 and CD8 T cells equally. Unlike CD87, CD98 and CD147 antibodies, which inhibited activation of both CD45RA (naive) T cells and CD45RO (memory) T cells, CD13 and CD148 appeared to be involved in activation of naive cells only. The molecules identified in this study have not previously been demonstrated to play a role as accessory molecules on DC, the cells that are pivotal for immune induction. Therefore they may provide new potential targets for modulation of the immune response at the APC level.

Protein degradation in MHC class II antigen presentation: opportunities for immunomodulation

Proteolysis is required for two steps of the MHC class II antigen-processing pathway, degradation of invariant chain and cleavage of protein antigens. Invariant chain dissociation from MHC is limited by a final proteolytic event which is tightly regulated in both temporal and tissue-specific ways. In contrast, enzymes involved in antigen proteolysis remain ill-defined. Gene 'knockout' experiments of housekeeping proteolytic enzymes suggest either that these enzymes do not play a major role, or that antigen proteolysis is too degenerate for this type of analysis. The possible role of two other proteinases, cathepsin E and aspariginyl endopeptidase is discussed. Finally, the data implicating antigen processing in repertoire generation is briefly considered. We conclude that selective regulation of endosomal proteolysis could have profound implications for control of immunity against infection, as well as in autoimmunity.

Vectorial function of major histocompatibility complex class II in a human intestinal cell line

This study explores the expression and the function of major histocompatibility complex class II in the intestinal epithelial cell line CaCo-2, which has been widely used as a model for the human gastrointestinal epithelium. Human leucocyte antigen (HLA)-DR expression on CaCo-2 cells is induceable by interferon-gamma (IFN-gamma), but responsiveness to IFN-gamma is dependent on cell differentiation and IFN-gamma availability at the basolateral cell surface. HLA-DR expression is concentrated in apical cytoplasmic vesicles and on the basolateral cell surface. Invariant chain is expressed in apical vesicles but is absent from the cell surface. Immunoprecipitation studies show a slow rate of dissociation of HLA-DR from Ii. Double labelling shows some overlap between HLA-DR expression and basolateral endosomal markers but no overlap with apical endosomal markers. Functional studies show processing and presentation of lysozyme endocytosed from the basolateral, but not apical surfaces. CaCo-2 cells may provide a useful model with which to dissect the antigen-processing pathways in polarized epithelial cells. The regulated access of antigens taken up from the gut lumen to the processing compartments may prevent overloading the immune system with antigens derived from normal gut contents.

Molecular characterization of U937-dependent T-cell co-stimulation

U937 cells provide a co-stimulatory signal for CD3-mediated T-cell activation which is independent of the CD28/CD80/CD86 interaction. This study set out to identify which molecules contribute to this co-stimulatory activity. Monoclonal antibodies (mAb) to the known accessory molecules CD11a, CD18, CD54 and CD45, all inhibited T-cell proliferation. Although CD11a/18 mAb inhibited U937/T-cell cluster formation as well as proliferation, CD45 enhanced the size of the clusters formed, suggesting that this was not the only mechanism of inhibition. The alternative co-stimulatory pathway provided by U937 cells preferentially stimulated a response in the CD18+ T-cell population, and this reflected the reduced sensitivity of CD8+ T cells to CD28-mediated activation. Monoclonal antibodies to three molecules, CD53, CD98 and CD147, also inhibited U937-dependent T-cell proliferation. The mAb to CD98 and CD147 were inhibitory when prepulsed on to the U937 cells, suggesting an effect mediated by these molecules on the antigen-presenting cell.

The role of reactive oxygen species in triggering proliferation and IL-2 secretion in T cells

This paper examines the hypothesis that reactive oxygen species (ROS) play an important role as second messengers in T cell activation. Activation of T cells with phorbol ester in combination with either calcium ionophore, or anti-CD3 antibody results in a large rapid flux of ROS activity. In contrast, co-stimulation with CD28 does not enhance ROS activity. The ROS signal was sensitive to ascorbic acid, desferrioxamine and dimethyl sulfoxide, suggesting that the major active species being generated was the hydroxyl radical, probably by iron-catalyzed decomposition of hydrogen peroxide. The generation of ROS in T cells was regulated by an accessory population within the peripheral blood. An anti-CD2 antibody induced a strong ROS flux, suggesting that the CD2/LFA-3 interaction may be important in this regulation. T cell activation was inhibited by the same panel of anti-oxidants as ROS generation, but much higher concentrations were required for inhibition of proliferation and IL-2 release than those required to block ROS generation. These data imply that ROS are not obligate second messengers for initiation of T cell activation. The results are compatible, however, with a role for activation-dependent T cell ROS generation in modulating the overall T cell response via autocrine and paracrine signalling pathways.

Reactive oxygen species activate human peripheral blood dendritic cells

This study investigates the effects of hydrogen peroxide, a potent oxygen free radical donor, on the phenotype and function of dendritic cells differentiated from peripheral blood precursors. We report that hydrogen peroxide induces an up-regulation of several dendritic cell surface markers involved in interaction with T cells, including MHC Class II molecules (DQ and DR) and the co-stimulatory molecules CD40 and CD86. Moreover we have observed that H2O2-treated dendritic cells are more efficient in promoting T cell proliferation than normal dendritic cells and that this enhancement can be blocked using the free radical scavenger agent N-acetylcysteine. Oxygen free radicals are a common by-product of inflammation, and our results suggest they may play an important role in activation of sentinel dendritic cells, linking tissue damage to the initiation of an adaptive immune response.

Responses to human rhinovirus in CD45 T cell subsets isolated from tonsil

Isotypes of CD45 have been used extensively as markers of memory and naive populations of T cells in peripheral blood. In this study, T cells were isolated from human tonsil and their proliferative response against human rhinovirus was measured. Unexpectedly, equivalent responses were found among the CD4+CD45RA+ and CD4+CD45RO+ populations of T cells. This response requires MHC class II-positive antigen-presenting cells. The time course of the T cell response in vitro was that of a classical recall response, and no proliferative response to the virus could be detected in human cord blood. These results suggest that tonsils contain a significant population of CD45RA+ memory cells. The presence of this population may reflect ongoing stimulation with this common infectious agent, and the anatomical location of the T cells within the major lymphoid organ draining the naso-pharyngeal epithelial surface.

Differential regulation of HLA-DQ expression by keratinocytes and Langerhans cells in normal and premalignant cervical epithelium

Keratinocytes in normal ectocervix did not express major histocompatibility complex class II molecules. In low-grade intraepithelial lesions expression was confined to HLA-DR, while in high-grade disease there was expression of HLA-DR and occasional expression of HLA-DQ. HLA-DR was expressed constitutively on the majority of Langerhans cells. In contrast, few Langerhans cells expressed HLA-DQ in normal cervix, but there was a steady upregulation of the proportion expressing HLA-DQ which paralleled the severity of disease. There was no direct correlation between human papillomavirus 16 and the expression of major histocompatibility complex class II by keratinocytes and Langerhans cells. Significant upregulation of HLA-DQ by Langerhans cells is observed in high-grade intraepithelial cervical lesions, suggesting antigen-presenting cell activation in papillomavirus-related premalignant disease.

From sentinel to messenger: an extended phenotypic analysis of the monocyte to dendritic cell transition

The transitional stages in the relationship between sentinel monocytes and messenger dendritic cells that are active in adaptive immunity, are, as yet, unclear. To explore these events, 2-hr adherent peripheral blood mononuclear cells were used either as monocytes, or cultured for 7 days with granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4) to generate dendritic cells, and the phenotypic features and relationship of the two cell populations was investigated using an extensive panel of monoclonal antibodies (mAbs). The features of the shift from monocyte to dendritic cell were also examined by daily phenotyping during the 7-day culture period. Twenty-five mAbs, most of which recognized known CD molecules, bound both monocytes and dendritic cells equally, whereas 19 mAbs exhibited differential staining. Four molecules not previously reported on dendritic cells were documented: CD87, CD98, CD147 and CD148. Seven cell-surface molecules (HLA-DQ, CD1a, CD13, CD30, CD43, CD63 and CD86) were expressed either at very low levels or not at all on monocytes, but had a strikingly increased expression on dendritic cells, suggesting a role in antigen presentation. The kinetics of monocyte to dendritic cell transition revealed a rapid activation phase within the first 24 hr, with a considerable increase in expression of the activation markers HLA-DR, CD13, CD14 and CD98; this was followed by a down-regulation of CD14 and a more gradual development of the other dendritic cell features over the remaining 6 days, with steady increases in CD1a, CD18, CD43, CD86, HLA-DR and HLA-DQ. Thus, these studies have demonstrated four novel components of the dendritic cell, and have documented the dynamic multistep nature of the process whereby an antigen-presenting dendritic cell phenotype may emerge from a monocyte precursor.

Modulation of antigen-specific T-cell activation in vitro by taurine chloramine

Taurine chloramine (TauCl) is produced during inflammation by reaction of hypochlorous acid (HOCl) with taurine, the most abundant free amino acid in neutrophils. We previously reported that TauCl inhibits the generation of macrophage inflammatory mediators such as nitric oxide, prostaglandin E2 (PGE2), tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6). In this study, the activity of TauCl in modulating T-cell activation was investigated. Treatment of T cells with TauCl (0.1-0.3 mM), prior to activation, was found to inhibit interleukin-2 (IL-2) release in response to both mitogen and antigen stimulation. Similarly, pretreatment of A-20 antigen presenting cells (APCs), at low cell numbers, was found to inhibit their ability to process and present ovalbumin (OVA) to a specific T-cell hybridoma. In contrast, pretreatment of higher numbers of A-20 cells with TauCl in the presence of OVA enhanced subsequent presentation of OVA. Finally, OVA modified with TauCl was processed and presented more efficiently than native OVA. Thus, TauCl is able to modulate induction of a specific adaptive immune response at several independent points of the overall antigen-presenting pathway.

Pure populations of transduced primary human cells can be produced using GFP expressing herpes virus vectors and flow cytometry

Herpes simplex virus (HSV) has often been suggested as a vector for gene delivery to the nervous system although it is also capable of infecting many other cell types. HSV also has the ability to package large genetic insertions so the expression of multiple genes from a single virus is possible. Here we show that a green fluorescent protein (GFP) expressing HSV1 vector can transduce two primary human cell types--quiescent human CD34+ hematopoietic progenitor cells and dendritic cells--which are both hard to transduce by other means. We also show that GFP is an effective marker when expressed from an HSV vector in vivo in the mouse brain. When GFP is expressed together with a second gene (in this case lacZ) from a single virus, transduced GFP-positive CD34+ hematopoietic progenitor cells or dendritic cells can both be generated at an effective efficiency of 100% for the second gene. Here transduction with the vector is combined with flow cytometry allowing GFP-positive cells to be sorted from the untransduced population. Such completely transduced populations of quiescent CD34+ hematopoietic progenitor and dendritic cells cannot easily be achieved by other means, and might thus allow experimental or therapeutic protocols to be carried out requiring high-level transduction which would not otherwise be possible. Such an approach using HSV vectors might also be applicable to other cell types for which transduction is as yet unreliable or of low efficiency.

Characterization of the T cell response to human rhinovirus in children: implications for understanding the immunopathology of the common cold

Human rhinovirus (HRV) is a frequent respiratory pathogen, responsible for a large proportion of cases of the "common cold" and linked to acute asthma, especially in children. T cell responses to HRV and their contribution to HRV-associated pathology were investigated. T cells were obtained from tonsils removed from children at routine tonsillectomy. Proliferative and cytokine responses were measured after in vitro restimulation with purified HRV preparations of both major and minor serotypes. Most tonsils tested showed T cell proliferation, and responses to multiple serotypes in one tonsil were observed frequently. Responding T cells were CD4-positive and produced interleukin-2 and interferon-gamma but no interleukin-4. Thus, children respond to HRV, a proportion of the response is serotype-cross-reactive, and a Th1 reaction predominates. In addition to contributing to protection, this response may enhance expression of virus receptor and be implicated in the immunopathology of HRV infection.

Enhancement of CD4+ T-cell-dependent interleukin-2 production in vitro by murine alveolar macrophages: the role of leukotriene B4

Local tissue macrophages are known to play a key role in regulation of adaptive immune responses, often by inhibition of T-cell activation and proliferation. In this study, we compare the influence of alveolar and peritoneal macrophages on T-cell-dependent interleukin-2 (IL-2) release. Alveolar macrophages, in contrast to peritoneal macrophages, enhance IL-2 release. Assay of a panel of potential macrophage-derived mediators indicated that activated alveolar macrophages stimulated greater release of IL-1 beta, tumour necrosis factor-alpha and, especially, leukotriene B4 (> 100 times) than activated peritoneal macrophages. Inhibition of prostaglandin synthesis by alveolar macrophages further enhanced the production of IL-2, while inhibition of leukotriene synthesis abolished the enhancement. The addition of exogenous prostaglandin E2 inhibited IL-2 release, while exogenous leukotriene B4 enhanced IL-2 release. When added simultaneously, the two compounds antagonized each other's activity. In conclusion, this study confirms that alveolar macrophages enhance IL-2 secretion, and suggests that this enhancement may be due at least in part to the very high rates of production of leukotriene B4. The overall influence of macrophage populations on T cells in vivo will reflect the complex balance between the multiple mediators produced within the local tissue microenvironment.

Cathepsin E expression by normal and premalignant cervical epithelium

We have investigated the expression of the aspartic proteinase cathepsin E and HLA-DR and the presence of HPV16 in normal squamous epithelium (n = 8) and low-grade (n = 21) and high-grade (n = 14) intraepithelial squamous lesions of the uterine cervix. Immunohistochemistry of cervical biopsies revealed that up-regulation of cathepsin E expression was related to increasing severity of the cervical intraepithelial neoplasia (CIN). Up-regulation of protein was associated with increased message as assessed by in situ hybridization. Langerhans cells and the majority of koilocytes did not express detectable cathepsin E levels. Although there was also an up-regulation of HLA-DR expression by cervical keratinocytes in cervical intraepithelial neoplasia lesions, as determined by immunohistochemistry, no significant correlation was found between HLA-DR and cathepsin E expression in these lesions; neither was expression of cathepsin E correlated to the presence of HPV16, detected by polymerase chain reaction. The expression of cathepsin E, an aspartic proteinase that is reported to play a role in antigen processing for presentation by class II major histocompatibility complex molecules, is associated with cellular dedifferentiation in cervical intraepithelial neoplasia.

Mechanisms for variability in a member of the scavenger-receptor cysteine-rich superfamily

This study reports a molecular analysis of pig WC1, a new member of the scavenger-receptor cysteine-rich (SRCR) superfamily. The pig WC1 contains up to six extra-cellular SRCR domains, highly homologous to other members of the family. However, the striking feature of the WC1 gene, as for its cattle and sheep homologues, is that it is present as a multigene family showing extensive sequence diversity, for both DNA and predicted protein sequence. The basis of this diversity was examined and was shown to be attributable to several different causes. These included single base-pair changes within SRCR domains, the optional usage of whole domains or exons, including a SRCR domain and the proximal "hinge" region, and alternative isoforms of the putative cytoplasmic tail. These results suggest that WC1 may code for a new, though more primitive type of antigen recognition structure specific for gamma/delta T cells.

Is there a role for nitric oxide in regulation of T cell secretion of IL-2?

Nitric oxide (NO) can have both effector (cytotoxic) and regulatory roles in immune function. In this study, we have re-examined the potential role of nitric oxide in mediating the macrophage-dependent suppression of IL-2 synthesis. In our model, TNP-specific CD4+ T cells are cocultured with Ag and either peritoneal or alveolar macrophages. Both populations of macrophages after in vitro stimulation with IFN-gamma can inhibit IL-2 release. In vitro stimulation also induces substantial levels of NO release by these macrophages, as well as high levels of prostaglandin E2 (PGE2). However, there was no correlation between NO levels and inhibitory activity. Furthermore, NG-monomethyl-L-arginine monoacetate, a specific inhibitor of NO release had no effect on IL-2 release, while indomethacin, which blocked prostaglandin synthesis, largely abrogated the suppressor activity of both macrophage populations. Although the addition of exogenous NO donors at high concentrations could inhibit IL-2 release by T cells, our data does not support the hypothesis that NO is a major macrophage mediator of suppression in this model.

Is there a role for nitric oxide in regulation of T cell secretion of IL-2?

Nitric oxide (NO) can have both effector (cytotoxic) and regulatory roles in immune function. In this study, we have re-examined the potential role of nitric oxide in mediating the macrophage-dependent suppression of IL-2 synthesis. In our model, TNP-specific CD4+ T cells are cocultured with Ag and either peritoneal or alveolar macrophages. Both populations of macrophages after in vitro stimulation with IFN-gamma can inhibit IL-2 release. In vitro stimulation also induces substantial levels of NO release by these macrophages, as well as high levels of prostaglandin E2 (PGE2). However, there was no correlation between NO levels and inhibitory activity. Furthermore, NG-monomethyl-L-arginine monoacetate, a specific inhibitor of NO release had no effect on IL-2 release, while indomethacin, which blocked prostaglandin synthesis, largely abrogated the suppressor activity of both macrophage populations. Although the addition of exogenous NO donors at high concentrations could inhibit IL-2 release by T cells, our data does not support the hypothesis that NO is a major macrophage mediator of suppression in this model.

Tumor-associated E6 protein of human papillomavirus type 16 contains an unusual H-2Kb-restricted cytotoxic T cell epitope

We previously showed that CTL from H-2b mice immunized against the E6 protein of human papilloma virus (HPV) type 16 recognized a 10-mer peptide corresponding to amino acids 131 to 140. We show in this study that the minimal epitope, 130 to 137, is a 8-mer peptide presented by H-2Kb class I molecules. At position P8, the 130 to 137 peptide contains a hydrophobic methionine anchor residue, but P3 and P5 do not contain the typical anchor residues that are frequently found in Kb-bound peptides. Analysis with alanine-substituted peptides indicates that the tryptophan at P3 acts as an alternative anchor mediating Kb binding, while an arginine at P2 is a TCR contact residue. Synthetic 9-mer peptides corresponding to residues 130 to 138 are as efficiently recognized by CTL as 130 to 137 peptides. Analysis of extracts of E6-expressing cells suggests that Ag processing may produce multiple peptides containing the minimal 130 to 137 epitope. In vitro binding studies indicate that Kb binding of peptide 130 to 137 is approximately five orders of magnitude less efficient than Kb binding of previously identified CTL epitopes. In contrast, the E6 protein contains another potential CTL epitope in the region of amino acids 41 to 50. A synthetic peptide spanning this region binds very strongly to Kb and is capable of stimulating a strong peptide-specific CTL response. In the context of the whole protein, however, this epitope remains cryptic.

Tumor-associated E6 protein of human papillomavirus type 16 contains an unusual H-2Kb-restricted cytotoxic T cell epitope

We previously showed that CTL from H-2b mice immunized against the E6 protein of human papilloma virus (HPV) type 16 recognized a 10-mer peptide corresponding to amino acids 131 to 140. We show in this study that the minimal epitope, 130 to 137, is a 8-mer peptide presented by H-2Kb class I molecules. At position P8, the 130 to 137 peptide contains a hydrophobic methionine anchor residue, but P3 and P5 do not contain the typical anchor residues that are frequently found in Kb-bound peptides. Analysis with alanine-substituted peptides indicates that the tryptophan at P3 acts as an alternative anchor mediating Kb binding, while an arginine at P2 is a TCR contact residue. Synthetic 9-mer peptides corresponding to residues 130 to 138 are as efficiently recognized by CTL as 130 to 137 peptides. Analysis of extracts of E6-expressing cells suggests that Ag processing may produce multiple peptides containing the minimal 130 to 137 epitope. In vitro binding studies indicate that Kb binding of peptide 130 to 137 is approximately five orders of magnitude less efficient than Kb binding of previously identified CTL epitopes. In contrast, the E6 protein contains another potential CTL epitope in the region of amino acids 41 to 50. A synthetic peptide spanning this region binds very strongly to Kb and is capable of stimulating a strong peptide-specific CTL response. In the context of the whole protein, however, this epitope remains cryptic.

The injured cell: the role of the dendritic cell system as a sentinel receptor pathway

A major unresolved paradox in immunology remains: how do we avoid harm, despite the abundant opportunities for induction of immune responses against self-proteins? Here, Mohammad Ibrahim, Benjamin Chain and David Katz extend Janeway's proposed explanation, arguing that adaptive immune responses are initiated not only by conserved microbial products, but also by microenvironmental tissue injury. They suggest that the key step is local dendritic cell activation, followed by upregulation of T-cell costimulatory molecules on these cells, and migration, leading to antigen presentation.

The gold anti-rheumatic drug auranofin governs T cell activation by enhancing oxygen free radical production

Gold-containing drugs continue to be used in the treatment of rheumatoid arthritis, but their mode of action remains unknown. One model to explain gold action is that gold-containing compounds can alter free radical production in cells of the immune system, but direct evidence for this hypothesis has been lacking. In this study we show that auranofin can enhance the rapid flux of reactive oxygen species (ROS), which accompanies phytohemagglutinin activation of peripheral blood T cells. Blocking this enhancement by the addition of antioxidants can reverse the functional effects of the drug on T cell responses, which we have previously demonstrated. These results provide strong experimental support for a model in which gold anti-rheumatics act by modulating ROS production. Furthermore, our experiments suggest that auranofin may be a useful tool to investigate the postulated role of ROS in the intra cellular T cell signaling pathway.

The role of non-adhesive T-cell-accessory cell interactions in the induction of T-cell proliferative hyporesponsiveness

We have suggested previously that induction of T-cell proliferative hyporesponsiveness is associated with a defective adhesive T-cell-antigen-presenting cell (APC) interaction. In the previous study, the hyporesponsiveness was allospecific, implying that a T-cell receptor-major histocompatibility complex (MHC) interaction had occurred. Therefore, we hypothesized that this type of non-adhesive T-cell-APC interaction might induce T-cell tolerance rather than activation. This hypothesis has now been tested further in the present study, using two experimental approaches. Firstly, L cells, which express a T-cell receptor ligand, i.e. MHC class II molecules, but lack the capacity to bind to T cells and do not express the crucial receptor/counter receptor lymphocyte function-associated antigen-1 (LFA-1)/intracellular adhesion molecule-1 (ICAM-1) pair, also induced non-allospecific T-cell proliferative hyporesponsiveness; this was not due to any direct inhibitory effect on the T cells. Secondly, monoclonal antibodies (mAb) directed to LFA-1 and ICAM-1 were used to disrupt T-cell-APC adhesion specifically, while allowing for T-cell receptor-MHC interaction to occur. The results of this new study suggest that the non-allospecific T-cell proliferative hyporesponsiveness induced was a function of direct T-cell inhibitory effects of these mAb. Taken together, these experiments add further evidence to support the notion that accessory cells which engage T-cell receptors without providing the necessary co-stimulatory signals induce T cells which are in a state of functional 'paralysis' with respect to the antigen which the T-cell receptor recognizes.

The effects of auranofin on activation and interleukin-2 release from human peripheral blood mononuclear cells

Auranofin, 30-300 nM causes a concentration-dependent potentiation of phytohaemagglutinin (PHA)-induced interleukin-2 (IL-2) release from human peripheral blood mononuclear cells in culture. At concentrations of auranofin between 1 and 3 microM, PHA-stimulated IL-2 release was inhibited, and the drug is cytotoxic at these concentrations. At concentrations of auranofin which potentiated PHA-induced IL-2 release, it had no effect on [3H]-thymidine incorporation. Auranofin, 3 to 300 nM caused a concentration-dependent increase in the population of peripheral blood mononuclear cells bearing the IL-2 receptor (Tac positive cells). Auranofin, 300 nM caused an increase of approximately 100% in the glutathione level within the resting cells, and also increased the glutathione level in PHA-stimulated cells. We conclude that auranofin acts early in the cell cycle, selectively to increase the release of IL-2 and the expression of Tac. The action of auranofin on cellular glutathione levels may alter the redox state of the cell which is known to be important in the control of transcription factor activation.

The interaction of auranofin and buthionine sulfoximine blocks activation of human peripheral T lymphocytes

We have previously demonstrated that auranofin, at nanomolar concentrations, enhances T cell activation, as measured by IL-2 release and Tac expression. However, it is not clear how enhanced T cell activation might be related to therapeutic value, since rheumatoid arthritis is widely believed to be associated with overactivation of the immune response. In this study, we show that the action of auranofin on T cell activation is dramatically influenced by the glutathione levels of the responding cells. Under conditions of very low intracellular glutathione where the synthesis of glutathione is blocked, the action of auranofin is converted from enhancement to a profound inhibition of T cell activation. Since glutathione levels in rheumatoid arthritis are known to be abnormally low, these results may explain how auranofin can act to suppress the immunological processes leading to rheumatoid arthritis. In addition, this study further demonstrated the close link which exists between auranofin action and glutathione metabolism in lymphocytes.

Differential regulation of cytokine production by nitric oxide

Nitric oxide (NO) has recently been identified as a potent and pleiotropic intracellular mediator produced by and acting on many cells of the body. Although considerable attention has been devoted to the regulation of NO by inflammatory cytokines, and also to the role of NO as an important effector molecule in immune function, there is very little information on the role of this mediator in modulating T-cell-dependent cytokine production. In this study we show that physiological levels of NO (either produced by activated macrophages or by the addition of exogenous NO donors) can selectively down-regulate interleukin-3 (IL-3) production by spleen cells from contact-sensitized mice, while leaving IL-2 activity unaffected. Thus NO may have an important role as an immunomodulatory as well as effector molecule in the immune system.

Epitope analysis of the T cell response to a complex antigen: proliferative responses to human rhinovirus capsids

Understanding the factors which regulate the repertoire of a T cell response is important when selecting T helper cell epitopes for inclusion in synthetic viral vaccines. In this study we have examined the T cell response to human rhinovirus (HRV) type 1 A in a mouse model system, using a comprehensive set of synthetic peptides which span all four of the proteins which make up the HRV capsid. This constitutes the first study to use a set of peptides covering the entire sequence of all structural proteins of any virus. This study identifies the major proliferative (CD4) T cell epitopes within the minor receptor group HRV 1 A, and analyzes these epitopes with relation to their location within the three-dimensional structure of the virus. The proliferative response to HRV is highly selective, with strong responses to only a very small number of epitopes, many of which are grouped together within restricted areas of the primary structure of the HRV proteins. The repertoire of the response is almost entirely specific to the major histocompatibility complex haplotype of the host. The major T cell epitopes are spatially distinct from the sites of the major antibody recognition sites, and are buried within the viral capsid. In striking contrast to the antibody responses, the T cell responses are highly cross-reactive against a wide variety of viral serotypes.

Characterization and functional analysis of the expression of intercellular adhesion molecule-1 in human papillomavirus-related disease of cervical keratinocytes

We have investigated the expression of intercellular adhesion molecule-1 (ICAM-1) in squamous neoplasia of the cervix and have noted a significant induction of the molecule in high-grade intra-epithelial lesions. Using monolayer and organotypic in vitro tissue culture systems, we have shown that there is no constitutive ICAM-1 expression on cervical keratinocytes immortalized but not transformed by human papillomavirus type 16, whereas two human papillomaviruses type 16 containing and fully transformed cervical keratinocyte lines do constitutively express the molecule. All cell types, including human papillomavirus-negative normal cervical keratinocytes, can be induced to up-regulate their expression of ICAM-1 by pro-inflammatory cytokines such as interferon-gamma. In addition, we have used an in vitro adhesion assay to show that ICAM-1:lymphocyte function antigen-1 interaction is functionally important in lymphocyte binding to cervical keratinocytes, suggesting a role for ICAM-1 in retaining and enabling functional activity of lymphocytes in the cervix in intraepithelial neoplasia.

Differential cytokine regulation by eicosanoids in T cells primed by contact sensitisation with TNP

Eicosanoids are important mediators of inflammation, but also play a role in regulation of lymphocyte function. In this study we have examined the function of both prostaglandins (PGs) and leukotrienes in regulating the release of a set of cytokines produced by T cells from mice primed with the contact-sensitising agent picryl chloride. Various patterns of response by different cytokines in response to exogenous eicosanoids were observed. Both interleukin-2 (IL-2) and interferon-gamma (IFN-gamma), two cytokines involved in activating the cellular contact sensitivity reaction, were downregulated by prostaglandin E2 (PGE2) and to a lesser extent by 6-keto PGF2 alpha (PGI2). In contrast, both PGE2 and PGI2 potentiated the release of IL-3 and IL-6 which both play an important role in stimulating haemopoesis after inflammation. Unexpectedly, IL-4 release was strongly inhibited by exogenous PGI2, while remaining unaffected by PGE2. This inhibition, in contrast to the PG-mediated effects on IL-2, IL-3, IL-6, and IFN-gamma was not due to increased intracellular levels of cAMP. In contrast to the strong immunomodulatory effects of PGs, leukotrienes B4 and C4 had only small and rather variable effects on any cytokine release.

Antigen processing and presentation of human rhinovirus to CD4 T cells is facilitated by binding to cellular receptors for virus

Human rhinovirus serotypes (HRV) fall into two distinct groups, major and minor, by virtue of their cell receptor-binding ability. In this study minor receptor-binding group viruses are demonstrated to bind directly to cells of the murine immune system, including lymphoid dendritic cells which act as antigen-presenting cells, although they do not produce a productive infection in murine cells. This binding is specific and can be blocked by other serotypes of minor-group HRV. Pre-treatment of HRV 1A, a minor-group virus, with HRV 1A-specific antibodies inhibited the cellular proliferation of murine virus primed T helper cells, whereas antibody treatment of HRV 15, a non-binding major serotype, gave no inhibition. The cell binding ability of minor-group HRV played a role in the overall immunogenicity of this virus group, which was shown to be enhanced compared to the immunogenicity of major-group viruses in mice.

Regulation of in vitro release of TH2 type cytokines (IL-4, IL-6) in the T cell response to the trinitrophenyl (TNP) hapten

We have investigated in vitro the ability of T cells from mice primed for contact hypersensitivity to release cytokines of the TH2 subtype, in particular IL-4 and IL-6. We demonstrate that both these cytokines are indeed produced by T cells from the lymph node and spleen of mice immunized by topical application of picryl chloride and restimulated in vitro by TNP-coupled spleen cells. However, the release of IL-4 is limited by the activity of IFN-gamma, a TH1 cytokine which we have previously shown is also produced after contact sensitization. Finally, induction of tolerance to TNP, by intravenous administration of antigen, or transfer of cells from tolerant mice into naive donors prior to sensitization (which suppresses the contact sensitivity reaction in the recipients) leads to a fall in IL-4 production. Thus neither tolerance nor suppression in this system is mediated by the antagonistic activities of TH1- and TH2-type T cells. In contrast, IL-6 production is upregulated during both suppression and tolerance, suggesting that this cytokine may play a part in the negative regulation of contact sensitivity.

Sensitization of allo-specific T lymphocytes in vivo: role of antigen-presenting cells

The migratory behavior of antigen-presenting cells was investigated in vivo. Purified murine splenic dendritic cells and splenic and peritoneal macrophages were labelled and injected subcutaneously in the hind foot-pads of mice and monitored for seven days. In the first 24 h, a small quantity of label was recovered from popliteal but not inguinal lymph nodes with radioactive (111In-oxine and 3H-uridine) but not fluorescent (1,1'-dioctadecyl 3,3,3'3'-tetramethylindocarbocyanine perchlorate and fluorescein isothiocyanate) labelling of the antigen-presenting cells. Chemical fixation of the injected antigen-presenting cells had no effect on the detection of label in the popliteal lymph nodes, suggesting that it was unlikely to be due to active cellular migration. Label recovery from hind feet declined with time over the seven day period and was independent of the label type. Essentially the same observations were made whether the antigen-presenting cells were syngeneic or allogeneic to the injected mice and irrespective of the type of antigen-presenting cell used. However, allogeneic antigen-presenting cells, which did not migrate to the draining lymph nodes, successfully primed T lymphocytes in these lymph nodes as shown by a secondary in vitro mixed leukocyte reaction. Again, chemical fixation of the injected antigen-presenting cells had no effect on their ability to prime allogeneic T lymphocytes in the draining lymph nodes. These experiments suggest that, during experimental allo-sensitization via the subcutaneous route, indirect priming of allogeneic T lymphocytes may be a dominant pathway.

Endocytosis by antigen presenting cells: dendritic cells are as endocytically active as other antigen presenting cells

Although dendritic cells are the most potent of all antigen presenting cells, they have paradoxically been regarded as having only a minimal capacity for endocytosis, which is a crucial step in antigen processing prior to presentation. Previous studies of dendritic cells, which are only available in small numbers, have been restricted to measurement of long-term endocytosis and so have stressed lysosomal accumulation. Measurement of traffic through late endosomes, which are closely related to the organelle in which antigen processing occurs, has, to date, required large numbers of cells and therefore has not been possible for dendritic cells. To resolve the paradox for dendritic cells, we have developed a flow cytometric assay of fluid-phase endocytosis that assesses late endosomal traffic by kinetic analysis of exocytosis in small numbers of cells. Using this assay, we show that fluid-phase endocytosis--in particular, traffic through late endosomes--is as active in dendritic cells as in other antigen presenting cells.

Adjuvant composition determines the induction of type II collagen-induced arthritis

In this study we have investigated the influence of adjuvant composition on the development of collagen-induced arthritis and of anti-collagen type II specific B- and T-cell responses following immunization with type II collagen. DBA/l mice immunized with bovine collagen type II emulsified in complete Freund's adjuvant (CFA) containing Mycobacterium tuberculosis strain H37Ra developed footpad swelling indicative of arthritis. Animals immunized with collagen type II plus CFA containing Mycobacterium butyricum, or incomplete Freund's adjuvant showed no significant increase in footpad width. Induction of anti-CII specific T-cell proliferation was also dependent upon immunization with CII plus CFA containing M. tb H37RA. In contrast, ovalbumin-reactive T-cell proliferation was unaffected by the species of mycobacteria, indicating that the difference in adjuvant activity of the mycobacterial species is specific for anti-collagen type II T-cell responses. Antibody response to collagen type II, unlike T-cell responses, was not significantly different using the two adjuvants. This study therefore demonstrates that murine collagen-induced arthritis requires immunization with collagen type II together with complete Freund's adjuvant containing Mycobacterium tuberculosis H37RA. Since only this combination of antigen and adjuvant induces detectable arthritis and T-cell responses against collagen type II, while antibody synthesis does not have such stringent adjuvant requirements, this suggests that the development of the full pattern of the collagen-induced arthritis disease requires synergistic activation of both humoral and cell-mediated responses.