Selective activation of Th1- and Th2-like cells in vivo--response to human collagen IV

Immune Modulation by Antigenic Peptides and Antigenic Peptide Conjugates for Treatment of Multiple Sclerosis

The immune system defends our body by fighting infection from pathogens utilizing both the innate and adaptive immune responses. The innate immune response is generated rapidly as the first line of defense. It is followed by the adaptive immune response that selectively targets infected cells. The adaptive immune response is generated more slowly, but selectively, by targeting a wide range of foreign particles (i.e., viruses or bacteria) or molecules that enter the body, known as antigens. Autoimmune diseases are the results of immune system glitches, where the body's adaptive system recognizes self-antigens as foreign. Thus, the host immune system attacks the self-tissues or organs with a high level of inflammation and causes debilitation in patients. Many current treatments for autoimmune diseases (i.e., multiple sclerosis (MS), rheumatoid arthritis (RA)) have been effective but lead to adverse side effects due to general immune system suppression, which makes patients vulnerable to opportunistic infections. To counter these negative effects, many different avenues of antigen specific treatments are being developed to selectively target the autoreactive immune cells for a specific self-antigen or set of self-antigens while not compromising the general immune system. These approaches include soluble antigenic peptides, bifunctional peptide inhibitors (BPI) including IDAC and Fc-BPI, polymer conjugates, and peptide-drug conjugates. Here, various antigen-specific methods of potential treatments, their efficacy, and limitations will be discussed along with the potential mechanisms of action.

The effect of antigen dose on T cell-targeting vaccine outcome

During the past 3-4 decades, an increasing amount of evidence has pointed to the complex role of the antigen dose or T cell receptor (TCR) stimulation strength on the subsequent type, duration and "flavor" or quality of the response. Antigen dose was initially shown to impact Th1/Th2 bias, and later also shown to differentially affect development and induction of Tregs, Th17, T-follicular helper (Tfh), cells, and others. In recent years the quality of both CD4/8 T cells during infections, cancer and/or autoimmunity has turned out to be critical for subsequent disease outcome. Importantly, different vaccination strategies also lead to different types of T cell responses, and the role of the antigen dose is emerging as an important factor as well as a tool for investigators to utilize in fine-tuning vaccine efficacy. This commentary will highlight essential background of how antigen dose can impact and affect the quality of T cell responses, and discuss how this translates in different vaccine settings.

[Pathogenic Mechanism and Diagnostic Testing for Drug Allergies]

　Three stages of the pathogenic mechanism of drug allergies can be considered: antigen formation, immune reaction and inflammation/disorder reaction. Drugs are thought to form 4 types of antigens: drug only, polymers, drug-carrier conjugates, and metabolite-carrier complexes. Antigens are recognized by B cell receptors and T cell receptors. Helper T cells (Th) are differentiated into four subsets, namely, Th1, Th2, Th17 and regulatory T cells (Treg). Th1 produces interleukin (IL)-2 and interferon (IFN)-γ, and activates macrophages and cytotoxic T cells (Tc). Macrophages induce type IV allergies, and Tc lead to serious type IV allergies. On the other hand, Th2 produces IL-4, IL-5, and IL-6, etc., and activates B cells. B cells produce IgE antibodies, and the IgE antibody affects mast cells and induces type I allergies. Activated eosinophil leads to the chronic state of type I allergy. Diagnostic testing for allergenic drugs is necessary for patients with drug allergies. Because in vivo diagnostic tests for allergenic drugs are associated with a risk and burden to the patient, in vitro allergy tests are recommended to identify allergenic drugs. In allergy tests performed in vitro, cytological tests are more effective than serological tests, and the leukocyte migration test (LMT) presently has the highest efficacy. An LMT-chamber is better than LMT-agarose in terms of usability and sensitivity, and it can detect about 80% of allergenic drugs.

High Antigen Dose Is Detrimental to Post-Exposure Vaccine Protection against Tuberculosis

Mycobacterium tuberculosis (Mtb), the etiologic agent of tuberculosis (TB), causes 1.8M deaths annually. The current vaccine, BCG, has failed to eradicate TB leaving 25% of the world’s population with latent Mtb infection (LTBI), and 5–10% of these people will reactivate and develop active TB. An efficient therapeutic vaccine targeting LTBI could have an enormous impact on global TB incidence, and could be an important aid in fighting multidrug resistance, which is increasing globally. Here we show in a mouse model using the H56 (Ag85B-ESAT-6-Rv2660) TB vaccine candidate that post-exposure, but not preventive, vaccine protection requires low vaccine antigen doses for optimal protection. Loss of protection from high dose post-exposure vaccination was not associated with a loss of overall vaccine response magnitude, but rather with greater differentiation and lower functional avidity of vaccine-specific CD4 T cells. High vaccine antigen dose also led to a decreased ability of vaccine-specific CD4 T cells to home into the Mtb-infected lung parenchyma, a recently discovered important feature of T cell protection in mice. These results underscore the importance of T cell quality rather than magnitude in TB-vaccine protection, and the significant role that antigen dosing plays in vaccine-mediated protection.

Antibodies to Type IV Collagen Induce Type 1 Autoimmune Pancreatitis

Type 1 autoimmune pancreatitis (AIP) is prototypic autoantibody-mediated diseases. Sclerosis accompanied by fiber deposition is generally regarded as the primary lesion in the development of obliterative vasculitis. However, why collagens or their antibodies play a crucial role in the pathogenesis of AIP has not been demonstrated. This study was performed to investigate if anti-collagen type IV antibodies (ACIVAbs) are the key factor of fiber deposition and recruit leukocytes, resulting in obliterative vasculitis in pancreas. Enzyme-linked immunosorbent analyses (ELISA) were used to measure the expression of Col IV and ACIVAbs in serum of patients with and without AIP. In vitro, adhesion and proliferation were determined by human lymphocytes incubated with Col IV and ACIVAbs. In vivo, C57BL0/6 mice were immunized with IgG-ACIVAbs, followed by analysis of clinical phenotype. IgG-ACIVAbs were recognized by the serum specimens from 12 of 22 patients with type 1 AIP, 3 of 9 patients with Crohn's disease, and 2 of 18 patients with pancreatic cancer, but not in healthy controls and acute pancreatitis. In patient's biopsy, ACIVAb staining increased and co-localized with subepithelial IgG4 deposits along the capillary walls and surrounding nerve fibers. In vitro, recombinant IgG-ACIVAbs increased leukocyte adhesion and proliferation. What is more, AIP could be induced in mice by immunization with IgG-ACIVAbs into adult mice.

On Peptides and Altered Peptide Ligands: From Origin, Mode of Action and Design to Clinical Application (Immunotherapy)

T lymphocytes equipped with clonotypic T cell antigen receptors (TCR) recognize immunogenic peptides only when presented in the context of their own major histocompatibility complex (MHC) molecules. Peptide loading to MHC molecules occurs in intracellular compartments (ER for class I and MIIC for class II molecules) and relies on the interaction of the respective peptides and peptide binding pockets on MHC molecules. Those peptide residues not engaged in MHC binding point towards the TCR screening for possible peptide MHC complex binding partners. Natural or intentional modification of both MHC binding registers and TCR interacting residues of peptides - leading to the formation of altered peptide ligands (APLs) - might alter the way peptides interact with TCRs and hence influence subsequent T cell activation events, and consequently T cell effector functions. This review article summarizes how APLs were detected and first described, current concepts of how APLs modify T cellular signaling, which biological mechanisms might force the generation of APLs in vivo, and how peptides and APLs might be used for the benefit of patients suffering from allergic or autoimmune diseases.

IL-2 limits IL-12 enhanced lymphocyte proliferation during Leishmania amazonensis infection

C3H mice infected with Leishmania amazonensis develop persistent, localized lesions with high parasite loads. During infection, memory/effector CD44(hi)CD4(+) T cells proliferate and produce IL-2, but do not polarize to a known effector phenotype. Previous studies have demonstrated IL-12 is insufficient to skew these antigen-responsive T cells to a functional Th1 response. To determine the mechanism of this IL-12 unresponsiveness, we used an in vitro assay of repeated antigen activation. Memory/effector CD44(hi)CD4(+) T cells did not increase proliferation in response to either IL-2 or IL-12, although these cytokines upregulated CD25 expression. Neutralization of IL-2 enhanced CD4(+) T cell proliferation in response to IL-12. This cross-regulation of IL-12 responsiveness by IL-2 was confirmed in vivo by treatment with anti-IL-2 antibodies and IL-12 during antigen challenge of previously infected mice. These results suggest that during chronic infection with L. amazonensis, IL-2 plays a dominant, immunosuppressive role independent of identifiable conventional T(reg) cells.

Role of cholinergic and cytokine regulation of T cell function in stimulation and inhibition of immune reactions in intoxication by organophosphorus compounds in different doses

Experiments on outbred albino rats showed that administration of acetylcholine and aceclidine in a dose of 0.1 LD50 for 3 days and of dimethyl dichlorovinyl phosphate (organophosphorus compound) in a single dose of 0.05 LD50 stimulated the function of Th1 and Th2 lymphocytes and cytokine production by these cells. Dimethyl dichlorovinyl phosphate in a single dose of 0.5 LD50 produced an opposite effect. Acetylcholine and aceclidine stimulated activity of acetylcholinesterase in T cells, while dimethyl dichlorovinyl phosphate in a single dose of 0.5 LD50 inhibited it. During acute intoxication, the organophosphorus compound, depending on the dose, can stimulate (acetylcholine effect) and inhibit the immune reactions (acetylcholinesterase inhibition of T cells).

HLA-DRB1 alleles control allergic bronchopulmonary aspergillosis-like pulmonary responses in humanized transgenic mice

BACKGROUND

Allergic bronchopulmonary aspergillosis (ABPA) is a lung hypersensitivity disease mediated in part by CD4(+) T(H)2 cells. There is a significant association between ABPA and the HLA-DR2 genotypes DRB1(*)1501 and DRB1(*)1503, whereas resistance might be associated with HLA-DRB1(*)1502.

OBJECTIVE

We sought to elucidate the role of HLA-DR alleles in allergic inflammation in lungs.

METHODS

HLA-DR humanized transgenic mice expressing either the susceptible or resistant alleles were analyzed for the nature and extent of pulmonary inflammation after exposure to Aspergillus species antigens.

RESULTS

Exposed DRB1(*)1501 and DRB1(*)1503 transgenic mice displayed infiltrates made up prominently of eosinophils, which is consistent with the inflammation found in ABPA. The resistant DRB1(*)1502 mice, on the other hand, displayed minimal to moderate inflammation, consisting mainly of T-cell infiltrates. Significantly more mucin was produced in the DRB1(*)1503 and DRB1(*)1501 mice, and their ability to limit the number of Aspergillus species conidia within the lung parenchyma was impaired. Despite their differences, both the DRB1(*)1503 and DRB1(*)1502 strains mounted comparable T cell-proliferative responses to Aspergillus species antigens.

CONCLUSION

The HLA-DR2 alleles DRB1(*)1501 and DRB1(*)1503 play a major role in the development of allergic pulmonary inflammation. In contrast, the HLA-DR2 allele DRB1(*)1502 mediates a nonallergic T(H)1-like response to the organism, possibly explaining an ABPA resistance factor. These results are in support of our published human studies in patients with cystic fibrosis and asthma.

CLINICAL IMPLICATIONS

HLA-DR typing in patients with cystic fibrosis and asthma will aid in the identification of individuals at risk for ABPA.

Expansion of CD4 T cells expressing a highly restricted TCR structure specific for a single parasite epitope correlates with high pathology in murine schistosomiasis

The hepatic immunopathology in schistosomiasis mansoni is mediated by CD4 T cells specific for egg antigens and varies considerably among mouse strains. Previous studies in high pathology C3H mice suggested that a strong T cell response was due to the recognition of an immunodominant epitope within the major egg antigen Sm-p40 (Sm-p40(234-246)). Using a panel of T cell hybridomas, we have now examined the egg antigen-specific TCR repertoire in two high pathology strains, C3H and CBA. We found that nearly half of the hybridomas responded to the Sm-p40(234-246 )epitope and, of these, nearly all expressed Valpha11.3 associated with Vbeta8. Furthermore, in response to egg antigen stimulation, transcript levels of Valpha11.3J36 (the most prevalent rearrangement expressed by Sm-p40(234-246)-specific hybridomas), increased in high pathology (CBA) but not in low pathology BALB/c strains. Our findings suggest that exacerbated schistosome egg-induced immunopathology can be driven by T cells expressing a highly restricted TCR structure specific for a single parasite epitope.

Antibody response to the surface envelope of caprine arthritis-encephalitis lentivirus: disease status is predicted by SU antibody isotype

This study evaluated the hypothesis that the disease status of Saanen goats infected with caprine arthritis-encephalitis lentivirus (CAEV) is associated with the focus of immune responses to viral antigens, particularly the surface envelope glycoprotein (SU). Specifically, we have proposed that Th2 responses promote progressive immune-mediated arthritis, whereas Th1 responses restrict virus replication and development of clinical disease. The present study determined the isotype of SU antibodies associated with progressor and long-term nonprogressor (LTNP) status. We show that chronically infected goats that develop clinical arthritis have predominantly IgG1 antibodies to SU during both preclinical and clinical stages of disease, whereas SU antibodies of LTNP goats are relatively biased toward IgG2. Additional studies determined the isotype of SU antibodies induced initially by CAEV infection. These experiments show that initial IgG1-dominated responses to SU are associated with subsequent development of preclinical inflammatory joint lesions, whereas lack of joint pathology is associated with an IgG2 bias of initial responses to SU. Our results using the CAEV model suggest that isotype bias of SU antibodies is a reliable indicator of clinical disease caused by lentiviruses. Isotype analysis may be a useful method to screen candidate lentiviral vaccines intended to prevent disease progression.

Induction of immune tolerance by neonatal intravenous injection of human factor VIII in murine hemophilia A

Inhibitory antibody formation is the most serious complication of factor (F)VIII replacement therapy in hemophilia A patients. FVIII-deficient mice were used to study new approaches for induction of immune tolerance. Neither antiFVIII inhibitory antibodies nor antiFVIII IgGs were observed in 13 of 14 adult mice that received 0.05 U g(-1) body weight of human FVIII intravenously within 24 h after birth and repeated injections as adults. In contrast, high FVIII antibody titers (>50 Bethesda Units mL(-1)) developed in seven of 13 mice injected on day 3 postpartum and in all adult mice not treated neonatally. One of nine mice and three of 17 mice developed high-titer antiFVIII inhibitory antibody when they were treated initially with 2-fold (0.1 U g(-1) body weight) and 10-fold higher doses (0.5 U g(-1) body weight) FVIII on day 0, respectively. A human FVIII-specific T-cell proliferative response was absent in splenocytes from neonatally treated mice. The tolerance was FVIII specific because antitoxoid antibodies developed after immunization with tetanus toxoid. Splenocytes failed to proliferate or produce interferon (IFN)-gamma in response to FVIII stimulation, yet still secreted interleukin-2. A proliferative response was restored with exogenous IFN-gamma or interleukin-12, suggesting that lack of inhibitor to FVIII was due to IFN-gamma-dependent anergy. Thus, exposure on day 0 to physiological levels of FVIII antigen might be important for induction of immune tolerance. This immune tolerance model may provide a basis for new approaches to prevention of FVIII inhibitors during replacement therapy.

Regulation of T helper cell differentiation in vivo by GP43 from Paracoccidioides brasiliensis provided by different antigen-presenting cells

Paracoccidioidomycosis, endemic in Latin America, is a progressive systemic mycosis caused by Paracoccidioides brasiliensis. The infection can evolve into different clinical forms that are associated with various degrees of suppressed cell-mediated immunity. Assuming that the effector immune response is a consequence of the preferential activation of either Th1 or Th2 subsets, in the present work we evaluated whether the nature of antigen-presenting cells (APCs) can influence the Th1/Th2 balance in vivo. It was observed that the injection of mature dendritic cells (DCs), macrophages and B cells primed the mice and induced a proliferation of T cells in vitro. It was seen that DCs from resistant mice stimulated predominantly interleukin-2 (IL-2) and interferon-gamma (IFN-gamma), whereas macrophages activated IL-10, IL-4 and IFN-gamma-secreting T cells and B cells IL-4 and IL-10 only. Results presented here clearly demonstrate that DC drives the development of cells secreting Th1-derived cytokines, whereas B cells induce the differentiation of a Th2 phenotype in vivo.

Immunopathogenesis of chlamydia trachomatis infections in women

OBJECTIVE

To develop a model of pathogenesis by which Chlamydia trachomatis progresses from acute to chronic infection, and finally serious disease (salpingitis, tubal occlusion).

DESIGN

Review of current literature located through web-based Medline searches using key words: Chlamydia trachomatis, immunology, cytokines, heat shock protein, infertility.

RESULT(S)

Cell-mediated immune mechanisms appear to be critical in determining whether acute infection is resolved or progresses into chronicity with pathological outcome. What determines the particular immune pathway depends on a range of determinants-HLA subtype and human genetics, cytokine profile, infectious load, route of infection, and endocrinology. A clearer picture of the natural history of chlamydial pathology may assist in providing better predictors of those women who may go on to develop significant sequelae after infection.

CONCLUSION(S)

Predicting those who may develop serious disease, including infertility, may contribute to improved management of such persons during earlier stages of infection and assist in prevention.

Specific antibody immune response against the parasitic portion of a glutathione-S-transferase fusion protein

The humoral immune response against an Entamoeba histolytica recombinant protein has been investigated. The 628 bp Bam HI-Eco RI DNA fragment (L1b) from the M11 cDNA clone, partially coding for a 220 kDa (L220) protein, was ligated in-frame into the pGEX-3X plasmid vector to produce the fusion protein GST-L1b. BALB/c mice were immunized with different doses of the GST-L1b fusion protein (10-500 microg). GST-L1b doses of 100/50/50, 300, or 500 microg induced an antibody response (IgG1>IgG3, IgG2a>IgG2b) specific for the amoebic part of the fusion protein (L1b). These antibodies were able to recognize the native protein in amoebic total extract. Anti-GST antibodies were not detected. On the other hand, doses of 10/10/10 or 200/100/100 microg induced antibodies able to recognize both GST (IgG2a>IgG1>IgG2b) and L1b (IgG1, IgG2a>IgG3>IgG2b). When mice were immunized with GST alone (100/50/50, 300 or 500 microg), antibodies against GST-L1b or GST were not detected. However, GST doses of 10/10/10 or 200/100/100 microg induced an antibody response able to recognize both GST-L1b and GST. We propose that an immunization protocol similar to the one used in this work may allow induction of high antibody titers specific against the parasite segment of a GST-fusion protein.

The vascular-associated lymphoid tissue: a new site of local immunity

Recent data suggest that atherosclerosis might be a systemic (auto)immune reaction against heat shock protein 60, first occurring at notorious local predilection sites, i.e. the intima at arterial branching points. The local infiltration of mononuclear cells, mainly macrophage-derived foam cells, T cells and smooth-muscle cells in atheromatous plaques, have long been described. During the past few years, research has been concentrated on the early stages in the development of atherosclerosis, and on healthy arteries from young individuals unaffected by arterial disease. In this review, we summarize data characterizing pre-existing mononuclear cell infiltrations in healthy arteries from children and teenagers. These arterial accumulations at regions known to be predilection sites for the later development of atherosclerosis consist mostly of activated T cells, macrophages and dendritic cells, with only a few mast cells and virtually no B or natural killer cells. In analogy to the mucosa-associated lymphoid tissue, we termed these accumulations 'vascular-associated lymphoid tissue', and assumed a similar function as a local immunosurveillance system, monitoring the bloodstream for potentially harmful endogenous or exogenous antigens. In addition to the remarkable accumulation of mononuclear cells, the vascular-associated lymphoid tissue regions are characterized by a typical distribution of extracellular matrix proteins: collagen type I, collagen type III, fibronectin and tenascin are expressed preferentially in the vascular-associated lymphoid tissue region, whereas collagen type IV, collagen type V, collagen type VI and laminin show a homogenous distribution throughout all regions of the intima. Vascular adhesion molecules type 1, intercellular adhesion molecules type 1 and P-selectin are already present on the healthy endothelial cells of young children. Interactions between adhesion molecules, extracellular matrix components and cellular elements of the vascular-associated lymphoid tissue may provide the basis for the cellular accumulations in the vascular-associated lymphoid tissue regions and the possible development of atherosclerotic lesions later in life.

Novel B and T cell epitopes of chicken ovomucoid (Gal d 1) induce T cell secretion of IL-6, IL-13, and IFN-gamma

BACKGROUND

Chicken ovomucoid (OM, Gal d 1) has an important role in the pathogenesis of IgE-mediated allergic reactions to hen's egg white.

OBJECTIVES

The purpose of this study was to clarify the mechanisms of T cell recognition of ovomucoid using intact OM and chemically modified, characterized and homogeneous solid phase synthetic peptides covering the whole molecule.

METHODS

Eighteen overlapping peptides were prepared by solid phase F-moc polyamide peptide synthesis (SPPS), characterized and high-pressure liquid chromatography (HPLC) purified. The peptides, together with intact, denatured and oxidized OM, were used to stimulate patient-derived cell cultures for mapping T cell epitopes. Proliferation responses, T cell phenotype and cytokine secretion using peripheral blood mononuclear cells (PBMC) from eight individuals and T cell lines (TCL) derived from six hen's egg-allergic patients, were examined. In addition, intact, denatured, oxidized and deglycosylated OM, as well as the peptides solely or with their keyhole limpet haemocyanin (KLH) complexes, were tested. For locating IgE and IgG B cell epitopes, seven egg-allergic patient sera and three OM-polyclonal sera were used. Healthy non-allergic individuals were included as controls.

RESULTS

Seven peptides were recognized by specific IgE, while OM-specific TCL recognized 10 peptides. Six of the OM peptides were commonly recognized both by patient S-IgE and blood-derived TCL. Among those, one novel epitope, peptide OM 61-74, had the ability to bind IgE. Another peptide, OM 101-114, was recognized by IgE and IgG sera, but not by any of the TCLs. In contrast, the peptides OM 41-56, OM 71-84, OM 131-144 and OM 171-186 were exclusively T cell epitopes with no affinity to specific antibodies. Abundant TCL secretion of IFN-gamma, IL-6, IL-4, IL-13, IL-10 and TNF-alpha in response to OM stimulation indicates the contribution of Th2 as well as Th1/Th0 CD4+ cell subsets. For allergic patients moderate amounts of IFN-gamma, IL-13, and high amounts of IL-6, were secreted in response to TCL stimulation by OM peptides. High amounts of IL-6 were secreted in response to all molecular forms of OM (intact-, modified-OM and the peptides 71-84 and 51-64) when TCLs from two non-allergic donors were used.

CONCLUSIONS

One novel B cell epitope (OM 61-74) and 10 T cell epitopes have been identified. The most reactive epitopes of the OM molecule comprise the motifs 1-14 to 71-84, the overlapping peptide-pairs OM 121-134 and OM 131-144 and peptides OM 161-174 and 171-186. Peptides OM 1-14 and 171-186 are the only ones capable of inducing IL-4 secretion. Only one peptide (OM 11-24) induces IL-10 secretion. Those peptides recognized as both T and B cell epitopes or only T cell epitopes, have the potential to induce T cell secretion of moderate to high amounts of IL-13, IFN-gamma and particularly IL-6.

Retroviral antibody binding of the MHC class II molecule: a biochemical influence on CD4 T cell differentiation in HIV infection?

Retroviral antibody capable of binding to the major histocompatibility complex (MHC) Class II molecule has been documented in human immunodeficiency virus-1 (HIV-1)-infected patients. Interactions between the MHC Class II receptor and the T-cell receptor (TCR) are central to the immune response. Importantly, retroviral antibody possesses a much higher binding affinity for the MHC Class II receptor, when compared to the TCR. Experiments have manipulated a number of factors related to antigen-presenting cell (APC) interaction with differentiating T-cells. These studies have observed the effects of lowering antigen dose and reducing ligand density on precursor Th (T helper) cell differentiation. Studies have also examined the effect of downregulated MHC Class II receptors and co-stimulatory molecules on APC-Th cell interaction. In addition, the sequestration of antigens away from the Class II processing pathway has been studied. These investigations reveal a general trend that can determine whether a naive CD4 T-cell becomes a Th1 or Th2-like cell. If the experimental manipulation weakens the APC-Th cell interaction, a weak ligating TCR signal results. Consequently, a weak ligating TCR signal can influence precursor Th cells to become Th2-like cells. Retroviral antibody binding of MHC Class II receptors may mimic a number of experimental conditions responsible for creating a weak ligating TCR signal.

HLA-G has a concentration-dependent effect on the generation of an allo-CTL response

Human leucocyte antigen (HLA) -G is expressed on trophoblast cells during pregnancy, suggesting a role in protection of the semiallogeneic fetus. Published data suggest that HLA-G protects a cell against natural killer cell lysis. It has been hypothesized that HLA-G may also protect the fetus by preventing allo-cytotoxic T lymphocyte (CTL) responses. To test this hypothesis, we assayed the effects of various concentrations of purified HLA-G on CTL response in a mixed lymphocyte culture (MLC) system. We found that concentrations > or =0.1 microg/ml of HLA-G suppressed the allo-CTL response by 30-100% over the control, but, paradoxically, concentrations of 0.01-0.05 microg/ml of HLA-G augmented the allo-CTL response by 25-50% over the control. Concentrations < or = 0.001 microg/ml HLA-G had no effect. Addition of HLA-G to preprimed allo-CTL effector cells did not affect their killing ability. Allo-CTL suppressive doses of HLA-G induced a T helper type 2 (Th2) cytokine response, whereas allo-CTL-enhancing doses of HLA-G induced a Th1-type cytokine response. HLA-G purified from first-trimester placenta does not affect allo-proliferative responses nor does it alter the percentage of CD4+ or CD8+ T cells in MLCs. These findings support a potential role for HLA-G-mediated suppression of allo-CTL formation in normal pregnancies. In addition, the effects observed at lower concentrations of HLA-G may have interesting implications for the condition of pre-eclampsia in which concentrations of this HLA class I molecule are reduced.

Alteration at a single amino acid residue in the T cell receptor alpha chain complementarity determining region 2 changes the differentiation of naive CD4 T cells in response to antigen from T helper cell type 1 (Th1) to Th2

To study whether changes in the structure of a T cell receptor (TCR) at a single peptide-contacting residue could affect T cell priming with antigenic peptide, we made transgenic mice with a point mutation in the TCR alpha chain of the D10.G4.1 (D10) TCR and bred them to D10 beta chain transgenic mice. The mutation consisted of a leucine to serine substitution at position 51 (L51S), which we had already established contacted the second amino acid of the peptide such that the response to the reference peptide was reduced by approximately 100-fold. A mutation in the reference peptide CA134-146 (CA-WT) from the arginine at peptide position 2 to glycine (R2G) restored full response to this altered TCR. When we examined in vitro priming of naive CD4 T cells, we observed that the response to doses of CA-WT that induced T helper cell type 1 (Th1) responses in naive CD4 T cells from mice transgenic for the D10 TCR gave only Th2 responses in naive CD4 T cells derived from the L51S. However, when we primed the same T cells with the R2G peptide, we observed Th1 priming in both D10 and L51S naive CD4 T cells. We conclude from these data that a mutation in the TCR at a key position that contacts major histocompatibility complex-bound peptide is associated with a shift in T cell differentiation from Th1 to Th2.

The functional role of class II-associated invariant chain peptide (CLIP) in its ability to variably modulate immune responses

During the process of class II MHC assembly and cell surface expression, the class II-associated invariant chain peptide (CLIP) is removed from the peptide-binding groove of MHC, a task mediated by H-2M. This allows binding and presentation of peptide epitopes. We have previously shown that exogenously added CLIP interferes with this process and down-regulates the cell surface expression of class II molecules. In this study, we explored the effect of exogenously added CLIP on antigen-specific immune responses. In vivo studies with CLIP and various peptide and protein antigens with different affinities for I-A(d) molecules demonstrated that CLIP variably affects the T cell-mediated immune responses. Immunization with CLIP along with the antigen induced a shift from a T(h)1- to T(h)2-like response as determined by the cytokine profile and antibody isotype. These results suggest that the presence of exogenous CLIP can significantly influence the presentation of antigen by class II MHC molecules to CD4 T cells and thereby modulate immune responses. Exogenously added CLIP rapidly localized into the subcellular compartment of antigen-presenting cells where MHC class II molecules are present. We suggest that exogenous CLIP reduces the loading of peptides on the class II molecules, thus down-regulating MHC-peptide complexes on the cell surface. Alternatively, CLIP may bind to cell surface class II molecules and this complex is rapidly internalized resulting in reduced cell surface MHC class II expression. The reduced level of MHC-peptide complexes favors the activation of T(h)2 cells over T(h)1 cells. These results have implications in the regulation of immune responses, particularly the prevention of certain autoimmune diseases where T(h)1-type responses are pathogenic and T(h)2-type responses are protective.

Role of corticosterone in realization of immunosuppressive effects in acute poisoning with toxic chemicals

Experiments on random-bred male rats shows that acute poisoning with metaphos and acrylonitrile inhibits mainly the thymus-dependent humoral immune response, delayed type hypersensitivity reaction, and activities of natural killers and K cells. The increase in plasma corticosterone under the effect of metaphos ensures the participation of this hormone in the realization of suppression of natural killers and thymus-dependent humoral immune response (production of IgG), the contribution of the hormone to this suppression being 35.6 and 35.1%, respectively. Suppression of immune reactions by acrylonitrile is not associated with corticosterone effect.

Approaches to improve engineered vaccines for human immunodeficiency virus and other viruses that cause chronic infections

We used several approaches to develop enhanced vaccines for chronic viral infections such as human immunodeficiency virus (HIV) and hepatitis C virus (HCV). 1) Selected epitopes were used to avoid potentially harmful immune responses. 2) Linkage between helper and cytotoxic T-lymphocyte (CTL) epitopes was found to be important. 3) We developed an "epitope enhancement" approach modifying the sequences of epitopes to make more potent vaccines, including examples for HIV and HCV epitopes presented by murine class II and human class I major histocompatibility complex (MHC) molecules. 4) CTL avidity was found to be important for clearing viral infections in vivo, and the mechanism was examined. High-avidity CTLs, however, were found to undergo apoptosis when confronted with high-density antigen, through a mechanism involving tumor necrosis factor (TNF), TNF-RII, and a permissive state induced through the T-cell receptor. 5) We employed cytokines in the adjuvant to steer immune responses toward desired phenotypes, and showed synergy between cytokines. 6) Intrarectal immunization with peptide vaccine induced mucosal and systemic CTL. Local mucosal CTL were found to be critical for resistance to mucosal viral transmission and this resistance was enhanced with mucosally delivered interleukin-12. 7) We used an asymmetry in induction of mucosal and systemic immune responses to circumvent pre-existing vaccinia immunity for use of recombinant vaccinia vaccines.

Bovine insulin and porcine or human insulin prime distinct CD4(+) T cell subsets in C57BL/6 mice

H-2(b) mice produce insulin-specific antibody when injected with bovine but not porcine or human insulin. Nevertheless, CD4(+) T cells have been cloned from C57BL/6 mice primed with porcine, human, and bovine insulin. Here we tested the hypothesis that CD4(+) T cells from C57BL/6 mice primed with porcine or human insulin are functionally distinct from those primed with bovine insulin. Our results show that variants of insulin that stimulate antibody responses induced Th2 clones, whereas variants of insulin that fail to stimulate antibody induced Th0 clones. Th0 clones triggered delayed-type hypersensitivity (DTH) in adoptive recipients, whereas Th2 clones did not. Insulin variants that primed Th0 clones also directly primed for DTH responses, while variants that activated Th2 clones did not. Thus, induction of Th2 clones correlated with the ability of mice to make antibody responses to insulin while development of Th0 clones correlated with DTH responses and the failure to produce antibody.

Subclass specificity of autoantibodies against myosin in patients with idiopathic dilated cardiomyopathy: pro-inflammatory antibodies in DCM patients

Detection of antimyosin antibodies in non-inflammatory cardiac disease undermines their disease specificity as a sensitive marker of damage in dilated cardiomyopathy (DCM) patients. Antibody subclass specificity could provide a more sensitive marker of disease and possibly discriminate the humoral autoimmune responses in different cardiac diseases. Frequency and reactivity of autoantibodies against alpha- and beta-isoforms of myosin heavy chain (mhc) were evaluated by ELISA for IgG, IgM, and subclasses IgG1, IgG2, and IgG3 in patients with DCM (NYHA III/IV, n = 82), end stage ischemic heart disease (E-IHD: NYHA III/IV, n = 62), mild ischemic heart disease (NYHA I/II, n = 27), and controls (n = 54). Autoantibodies against atrial and ventricular myosin were raised in heart failure patients compared to mild-IHD and controls but with different antigen affinities. Reactivity in E-IHD was significantly raised against (ventricular) beta-mhc compared with only mild-IHD patients, suggesting a relative increase in ventricular specific antibodies in IHD patients with a higher NYHA class. IgG subclass analysis for IgG1, IgG2, and IgG3 against alpha- and beta-mhc showed statistically raised levels of IgG3 only in DCM patients and a significantly higher reactivity of IgG2 in heart failure patients versus controls. The results demonstrate immunological heterogeneity of antimyosin antibodies developed in different clinical entities. Pro-inflammatory characteristics of IgG3 antibodies in a select group of patients with DCM may contribute to autoimmune mechanisms of injury in these patients.

Inability of interleukin-12 to modulate T-helper 0 effectors to T-helper 1 effectors: a possible distinct subset of T cells

Interleukin-12 (IL-12) strongly favours the development of T-helper 1 (Th1)-type cells through its ability to induce interferon-gamma (IFN-gamma) production by natural killer cells and T cells. In the present work we analysed the effects of IL-12 on the synthesis and secretion of IFN-gamma and IL-4 by human T-cell clones. Several previously described human T-cell clones exhibiting Th1, Th2 or Th0 phenotypes were used for these analyses. We demonstrated, by enzyme-linked immunosorbent assay (ELISA) and intracytoplasmic staining, that, in Th0 clones, IL-12 up-regulated the production of both IFN-gamma and IL-4 and was unable to modulate these cells to Th1-type. The up-regulation of cytokine gene expression was transcriptionally regulated and was not due to differences in mRNA stability. In Th1 cells, IL-12 up-regulated only IFN-gamma and not IL-4. However, in Th2 cells, both IFN-gamma and IL-4 were up-regulated by IL-12. This suggests that Th2 cells may be less stable than Th1 cells. We also observed that human Th2 cells expressed the IL-12beta2 receptor, in contrast to murine Th2, which lacks this receptor. The observed differences in the effects of IL-12 on the three T-cell subsets may have important ramifications for IL-12-based therapies.

Levels of IL-12 in the sera of patients with systemic lupus erythematosus (SLE)--relation to Th1- and Th2-derived cytokines

IL-12 is a cytokine that induces Th1-derived cytokines (interferon-gamma (IFN-gamma) and IL-2). The significance of IL-12 in human autoimmunity is no clear, and the serum levels of IL-12 in SLE are not clearly established. Therefore, we examined the levels of IL-12 in 39 patients with active SLE, with sandwich ELISA. The levels of IL-12 in patients were significantly higher than in normal subjects. Patients with high levels of IL-12 also had high levels of IFN-gamma, while their levels of IL-13 were significantly lower than in patients with normal levels of IL-12. Patients with pulmonary involvement had high levels of IL-12, and steroid therapy decreased the IL-12 level in three patients. In a retrospective study of seven patients, various changes of IL-12 and IL-13 were recognized before disease flare. Thus, in SLE patients, the level of IL-12 was increased and this increase was related to the change of Th1- or Th2-derived cytokines with some organ involvement.

T helper differentiation proceeds through Stat1-dependent, Stat4-dependent and Stat4-independent phases

Much of our focus in understanding Th1/Th2 development has been on the signals delivered by IL-12 and IL-4 as final determinants of terminal T cell differentiation. Because extinction of IL-12 signaling in early Th2 development could potentially be important in imprinting a more permanent Th2 phenotype on a population of T cells, we have also examined various parameters regulating the IL-12 signaling pathway. Whereas IL-4 appears to repress functional IL-12 signaling through inhibition of IL-12R beta 2 expression, IFN-gamma in the mouse, and IFN-alpha in the human appear to induce IL-12R beta 2 expression and promote IL-12 responsiveness. We propose that Th1 development can be considered in two stages, capacitance and development. Capacitance would simply involve expression of IL-12R beta 1 and beta 2 subunits, regulated by TCR, IL-4 and IFNs. The second stage, development, we propose is the true IL-12 induced developmental stage, involving expression of Stat4 inducible proteins. In the human, this may also occur via IFN-alpha, which is able to activate Stat4. It is perhaps possible that all of Stat4 actions on Th1 development may be exert directly by Stat4 at the IFN-gamma gene, however we suggest that, more likely, Stat4 may act to induce Th1 development through the induction of other non-cytokine genes, whose stable expression maintains the transcriptional state of a Th1 cell.

A novel role for the major histocompatibility complex class II transactivator CIITA in the repression of IL-4 production

Class II transactivator (CIITA) is known as a coactivator for MHC class II gene expression in antigen-presenting cells. Surprisingly, when CIITA-/- CD4 T cells were stimulated in the presence of IL-12, they produced not only IFNgamma but also high levels of IL-4. The IL-4 production is due to the accumulation of IL-4 gene transcripts in Th1 cells. This transcriptional control is observed in T cells differentiating to the Th1 but not Th2 lineage, consistent with induction of expression of the CIITA gene in T cells by IFNgamma. Thus, in addition to its role in transactivation of genes involved in antigen presentation, CIITA plays a critical role during the T cell differentiation by negatively regulating the IL-4 gene transcription.

The optimization of helper T lymphocyte (HTL) function in vaccine development

Helper T lymphocyte (HTL) responses play an important role in the induction of both humoral and cellular immune responses. Therefore, HTL epitopes are likely to be a crucial component of prophylactic and immunotherapeutic vaccines. For this reason, Pan DR helper T cell epitopes (PADRE), engineered to bind most common HLA-DR molecules with high affinity and act as powerful immunogens, were developed. Short linear peptide constructs comprising PADRE and Plasmodium-derived B cell epitopes induced antibody responses comparable to more complex multiple antigen peptides (MAP) constructs in mice. These antibody responses were composed mostly of the IgG subclass, reactive against intact sporozoites, inhibitory of schizont formation in liver invasion assays, and protective against sporozoite challenge in vivo. The PADRE HTL epitope has also been shown to augment the potency of vaccines designed to stimulate a cellular immune response. Using a HBV transgenic murine model, it was found that CTL tolerance was broken by PADRE-CTL epitope lipopeptide, but not by a similar construct containing a conventional HTL epitope. There are a number of prophylactic vaccines that are of limited efficacy, require multiple boosts, and/or confer protection to only a fraction of the immunized population. Also, in the case of virally infected or cancerous cells, new immunotherapeutic vaccines that induce strong cellular immune responses are desirable. Therefore, optimization of HTL function by use of synthetic epitopes such as PADRE or pathogen-derived, broadly crossreactive epitopes holds promise for a new generation of highly efficacious vaccines.

Pattern of immune response to GP43 from Paracoccidioides brasiliensis in susceptible and resistant mice is influenced by antigen-presenting cells

Paracoccidioidomycosis (PCM), endemic in Latin America, is a progressive systemic mycosis caused by Paracoccidioides brasiliensis. The infection can evolve to different clinical forms that are associated with various degrees of suppressed cell-mediated immunity. In the murine model, A/Sn and B10.A isogenic strains of mice are known to be resistant and susceptible, respectively, to this fungal infection. Assuming that the effector immune response is a consequence of the preferential activation of either Th1 or Th2 subsets, in the present work we evaluated the importance of two antigen-presenting cells (APCs), macrophages and B cells, in the development of the immune response to P. brasiliensis. In resistant mice, purified gp43, the main antigenic component of P. brasiliensis, seems to have been preferentially presented by macrophages and stimulated Th1 lymphokine production. On the other hand, in susceptible animals gp43 was distinguishably presented by B cells, which led to stronger activation of Th2 subsets. Moreover, T cells from resistant mice responded as those from susceptible animals when stimulated by gp43 presented by APCs from susceptible mice and vice versa, indicating that there are no significant differences in the T cell repertoires from A/Sn and B10.A mice. When T cells from F1 (A/Sn x B10.A) mice were stimulated by gp43 presented by APCs from A/Sn or B10.A, impaired behavior of B10.A macrophages in activating Th1 cells and a B10.A B cell tendency to stimulate T cells that secrete higher levels of IL-10 were observed. Taken together, our results suggest that APCs may be implicated in the outcome of P. brasiliensis infection.

High Antigen Density and IL-2 Are Required for Generation of CD4 Effectors Secreting Th1 Rather Than Th0 Cytokines

We reevaluated the effects of Ag dose on the polarization of CD4 effectors generated in vitro from naive pigeon cytochrome c-specific TCR transgenic T cells under conditions in which we could eliminate contaminating non-naive CD4 cells and the effects of heterogeneous Ag-presenting populations. When the possibility of contaminating non-naive T cells was reduced by using T cells from transgenic mice on a RAG-2−/− background, Ag dose did not have a significant effect in Th1 and Th2 polarization unless exogenous IL-2 was initially added to cultures. Effectors generated were uniformly Th0 but produced only IL-2 in substantial amounts. When exogenous IL-2 was added to priming cultures, T cells secreting a Th0 phenotype (large quantities of IL-2, IL-4, IL-5, and IFN-γ) developed, except at very high doses of Ag, where there was a striking reduction in IL-4 and IL-5 secretion. Our results imply that Ag dose does not have a direct effect on Th1/Th2 polarization, except under conditions that include a high level of TCR ligation and in the presence of high levels of IL-2, where production of Th2 cytokines may be down-regulated by a mechanism that is not yet clear.

CD4 Regulation of TCR Signaling and T Cell Differentiation Following Stimulation with Peptides of Different Affinities for the TCR

To define the role of CD4 in modulating T cell signaling pathways and regulating Th1 and Th2 differentiation, we have examined the activation and differentiation characteristics of naive T cells from CD4 mutant mice. Using peptides with differing affinities for the moth cytochrome c-specific TCR, we test the hypothesis that differences in coreceptor recruitment and signaling explain the qualitatively distinct signaling pathways seen in CD4 T cells following high affinity agonist and low affinity altered peptide ligand (APL) ligation. We find that the absence of CD4 signaling during stimulation with a strong agonist peptide does not qualitatively change the pattern of early TCR-mediated biochemical signaling events into a pattern resembling the response of CD4+ T cells to APLs. In contrast, the response to APL stimulation, by T cells bearing the same TCR, does require a component of CD4 signaling. The proliferative response and calcium signals normally seen following APL stimulation are markedly diminished in the absence of CD4. In addition, we find that naive T cell differentiation into Th2 effector cells is impaired in the absence of CD4. These data suggest that the altered pattern of biochemical signals generated by APLs require CD4 coreceptor function and that some of these signals may be required to initiate Th2 differentiation.

Autoimmune diabetes: the role of T cells, MHC molecules and autoantigens

Type 1 diabetes (IDDM) is a T cell mediated autoimmune disease which in part is determined genetically by its association with major histocompatibility complex (MHC) class II alleles. The major role of MHC molecules is the regulation of immune responses through the presentation of peptide epitopes of processed protein antigens to the immune system. Recently it has been demonstrated that MHC molecules associated with autoimmune diseases preferentially present peptides of other endogenous MHC proteins, that often mimic autoantigen-derived peptides. Hence, these MHC-derived peptides might represent potential targets for autoreactive T cells. It has consistently been shown that humoral autoimmunity to insulin predominantly occurs in early childhood. The cellular immune response to insulin is relatively low in the peripheral blood of patients with IDDM. Studies in NOD mice however have shown, that lymphocytes isolated from pancreatic islet infiltrates display a high reactivity to insulin and in particular to an insulin peptide B 9-23. Furthermore we have evidence that cellular autoimmunity to insulin is higher in young pre-diabetic individuals, whereas cellular reactivity to other autoantigens is equally distributed in younger and older subjects. This implicates that insulin, in human childhood IDDM and animal autoimmune diabetes, acts as an important early antigen which may target the autoimmune response to pancreatic beta cells. Moreover, we observed that in the vast majority of newly diagnosed diabetic patients or individuals at risk for IDDM, T cell reactivity to various autoantigens occurs simultaneously. In contrast, cellular reactivity to a single autoantigen is found with equal frequency in (pre)-type 1 diabetic individuals as well as in control subjects. Therefore the autoimmune response in the inductive phase of IDDM may be targeted to pancreatic islets by the cellular and humoral reactivity to one beta-cell specific autoantigen, but spreading to a set of different antigens may be a prerequisite for progression to destructive insulitis and clinical disease. Due to mimic epitopes shared by autoantigen(s), autologous MHC molecules and environmental antigens autoimmunity may spread, intramolecularly and intermolecularly and amplify upon repeated reexposure to mimic epitopes of environmental triggers.

Apoptosis and thyroiditis

The origin of the various forms of autoimmune thyroiditis remains unclear. Most investigations into the pathogenesis of these disorders have focused on immune abnormalities that might lead to an autoimmune response. However, no unique immune response to thyroid autoantigens has been identified that either is limited to patients with thyroiditis or is absolutely correlated with clinical disease expression. CD8 T-cell-mediated cytotoxicity is thought to be a major cause of thyroid follicular cell damage in thyroiditis. This damage is produced in part through the induction of apoptosis in thyroid cells. Recent studies have demonstrated that programmed cell death is regulated in thyroid cells and that a major pathway for immune-mediated apoptosis, the Fas pathway, is blocked by labile inhibitors in a manner that could prevent cytotoxicity. This review also examines several other types of regulation of apoptotic pathways in thyrocytes. We hypothesize that the regulation of programmed cell death pathways in the thyroid may alter the expression of autoimmune thyroid diseases by modifying the susceptibility of thyroid cells to immune-mediated apoptosis.

Correlation of platelet Fc gammaRIIA polymorphism in refractory idiopathic (immune) thrombocytopenic purpura

Fc gammaRIIA, a low affinity receptor for IgG, is a polymorphic molecule: Fc gammaRIIA-HH131, Fc gammaRIIA-HR131 and Fc gammaRIIA-RR131. This polymorphism influences the efficiency of the receptor to bind with IgG2. Recent reports on altered distribution amongst individuals with heparin-induced thrombocytopenia (HIT) prompted us to examine the Fc gammaRIIA polymorphism in a cohort of patients with refractory idiopathic (immune) thrombocytopenic purpura (ITP), in whom severe disease had required them to undergo splenectomy. 29 post splenectomy ITP individuals and 61 normal controls were investigated. Polymerase chain reaction (PCR) and a Southern blotting technique were used to determine the Fc gammaRII polymorphism. Although the distribution of the allotypes of Fc gammaRIIA in the control population was similar to that found in other European studies of Caucasian populations (15 (25%) HH131; 35 (57%) HR131; 11 (18%) RR131), the patient group was skewed towards the RR131 allotype which has least efficiency for IgG2 binding (3 (10%) HH131; 12 (42%) HR131; 14 (48%) RR131; P<0.005). These findings suggest that Fc gammaRIIA polymorphisms may be implicated in the pathophysiology of ITP or may be responsible for modulating the immune response in this heterogeneous autoimmune disease.

Differential migration of Th1 and Th2 cells--implications for vaccine and infection studies

Most lymphocytes migrate continuously between the blood and lymphatic system. This migration does not occur randomly and shows some bias for specific tissue compartments. In particular, CD4+ memory T cells have been shown to preferentially migrate to either peripheral or mucosal lymph nodes depending on their site of origin. The selective migration of lymphocytes into lymph nodes is facilitated by the differential expression of adhesion molecules on the lymphocyte surface interacting with their respective ligands on endothelial cells lining the capillary vessels. The acquisition of these 'mucosal' or 'peripheral' homing receptors was thought to be dictated by the particular tissue site in which lymphocyte were activated. A large amount of recent experimentation has shown that memory T cells generated against infectious agents can have different functional phenotypes as determined by their cytokine secretion patterns. Two of these distinct functional phenotypes. Th1 and Th2 cells, are differentially induced in peripheral and mucosal lymph nodes and recent data has suggested that the observed tissue-specific migration of memory T cells may be determined by this functional phenotype rather than the site of activation. Data in support of this new hypothesis are presented in this paper. In addition, as both the functional and surface phenotype of lymphocytes is dependent on local hormonal and cytokine environments, lymphocyte migration patterns may be manipulated by vaccination and infection.

Newborn Mice Develop Balanced Th1/Th2 Primary Effector Responses In Vivo But Are Biased to Th2 Secondary Responses

Newborn mice are impaired in their abilities to mount protective immune responses. For decades, it was generally held that the poor responses of newborns were largely due to the developmentally immature state of the T cells. In vitro studies showing that neonatal T cells were deficient in Th1 cytokine production, proliferation, and secondary responsiveness strongly supported this idea. Recently, several studies have challenged this view; animals exposed to Ag as neonates were shown to have mature Th1 responses in adulthood. However, it is not clear whether the mature immune responses were actually mounted by T cells generated after the neonatal stage. We have reexamined this issue by analyzing the capabilities of neonatal lymph node T cells to develop into Ag-specific effector cells during the actual neonatal period. Our results demonstrate that the capacity to develop a balanced Th1/Th2 primary effector response is fully mature within the first week of life. However, while neonatal and adult primary cytokine profiles were very similar, Th2 secondary responses predominated in animals first immunized as newborns. Moreover, we have observed other differences between adults and neonatal responses, including 1) the kinetics of cytokine production and responsiveness to adjuvant during the primary response, and 2) the contribution of spleen and lymph node to secondary responses. We propose that these differences reflect developmental regulation of effector cell function that has important consequences to neonatal immune function.

Differential regulation of human T cell cytokine patterns and IgE and IgG4 responses by conformational antigen variants

Bee venom phospholipase A2 (PLA) represents the major allergen and antigen in allergic and non-allergic individuals sensitized to bee sting. We have studied specific activation of peripheral T cells by different structural and conformational variants of PLA and secretion of cytokines regulating IgE and IgG4 antibody (Ab) formation. PLA molecules expressing the correctly folded tertiary structure, which show high affinity to membrane phospholipids and were recognized by Ab from bee sting allergic patients, induced high IL-4, IL-5 and IL-13 production in peripheral blood mononuclear cell cultures. In contrast, non-refolded recombinant PLA (rPLA) and reduced and alkylated native PLA (nPLA) induced more IFN-gamma and IL-2 and higher proliferative responses. Differences in proliferation and cytokine patterns among correctly folded and non-refolded PLA resulted from conformation-dependent involvement of different antigen-presenting cell (APC) types. Antigen (Ag)-presenting B cells recognized PLA only in its natural conformation, stimulated Th2 type cytokines and induced IgE Ab. Non-refolded PLA was recognized, processed and presented exclusively by monocytes and induced a Th1 dominant cytokine profile leading to IgG4 production by B cells. The possibility that production of particular cytokine patterns and Ig isotype was influenced by the enzymatic activity of PLA was excluded by using enzymatically inactive H34Q point-mutated, refolded rPLA. These findings demonstrate the decisive role of specific Ag recognition by different APC, depending on structural features, membrane phospholipid binding property and the existence of conformational B cell epitopes, in the differential regulation of memory IgE and IgG4 Ab. Furthermore, they show that a change from IgE-mediated allergy to normal immunity against a major allergen can be induced by rPLA variants that are not recognized by specific Ab and B cells but still carry the T cell epitopes. These features may enable new applications for safer immunotherapy.

Dendritic cells from Peyer's patch and spleen induce different T helper cell responses

The role of antigen-presenting cells (APC) in regulating the balance of T helper type 1 (Th1) and T helper type 2 (Th2) responses and cytokine production is unclear. Dendritic cells (DC), the most potent APC for naive T cell activation, were found to regulate Th1 and Th2 cytokine profiles in a manner dependent on their tissue of origin. Using whole tissues or purified cell mixtures, spleen (systemic) DC were found to induce mainly Th1 cytokines, and Peyer's patch (mucosal) DC were found to induce predominantly Th2 cytokines. Spleen DC induced high levels of interferon-gamma (IFN-gamma) or interleukin-2 (IL-2) or both, and Peyer's patch DC induced IL-4 or IL-6 or both in spleen and Peyer's patch T cells, allogeneic mixed leukocyte reactions, or antigen-specific Th0 clones. These data suggest that the tissue of origin of DC has a significant impact on subsequent T cell development.

Susceptibility to anti-glomerular basement membrane disease and Goodpasture syndrome is linked to MHC class II genes and the emergence of T cell-mediated immunity in mice

We developed a new mouse model of human anti-glomerular basement membrane (GBM) disease to better characterize the genetic determinants of cell-mediated injury. While all major histocompatibility complex (MHC) haplotypes (H-2a, k, s, b, and d) immunized with alpha3 NC1 domains of type IV collagen produce anti-alpha3(IV) NC1 antibodies that cross-react with human Goodpasture [anti-GBM/anti-alpha3(IV) NC1] autoantibodies, only a few strains developed nephritis and lung hemorrhage associated with Goodpasture syndrome. Crescentic glomerulonephritis and lung hemorrhage were MHC-restricted in haplotypes H-2s, b, and d (A beta/A alpha region in H-2s) and associated with the emergence of an IL-12/Th1-like T cell phenotype. Lymphocytes or anti-alpha3(IV) NC1 antibodies from nephritogenic strains transfer disease to syngeneic recipients. However, passive transfer of isogenic alpha3(IV) NC1 antibodies into -/- T cell receptor-deficient mice failed to produce nephritis. Finally, nephritis and its associated IL-12/Th1-like T cell response attenuate in disease-susceptible mice tolerized orally to alpha3(IV) collagen before immunization. Our findings suggest collectively, as a hypothesis, that anti-GBM antibodies in mice only facilitate disease in MHC haplotypes capable of generating nephritogenic lymphocytes with special T cell repertoires.

Infection with Salmonella typhimurium modulates the immune response to Schistosoma mansoni glutathione-S-transferase

Immune response polarization is controlled by several factors, including cytokines, antigen-presenting cells, antigen dose, and others. We have previously shown that adjuvants and live vectors play a critical role in polarization. Thus, immunization with the Schistosoma mansoni 28-kDa glutathione-S-transferase (Sm28-GST) in aluminum hydroxide induced a type 2 cytokine profile and the production of immunoglobulin G1 (IgG1)- and IgE-specific antibodies. In contrast, mice infected with recombinant Salmonella typhimurium expressing Sm28-GST developed a type 1 cytokine profile and produced IgG2a-specific antibodies against Sm28-GST and Salmonella antigens. In this study, to determine if S. typhimurium not expressing Sm28-GST would still influence the type of the response against this antigen, we compared the profiles of the immune responses generated against Sm28-GST administered in alum in mice infected and not infected with S. typhimurium. Infected mice generated both IgG1 and IgG2a antibodies against Sm28-GST, while noninfected mice produced only IgG1 anti-Sm28-GST antibodies. Moreover, interleukin-4 (IL-4) mRNA expression in infected mice was near background levels, while gamma interferon (IFN-gamma) mRNA expression in coinfected mice was significantly higher than in mice immunized with Sm28-GST in alum only. However, after antigen-specific stimulation in vitro with Sm28-GST, levels of IL-4 and IFN-gamma cytokine production were similar in the two groups of mice. These results suggest that (i) the immune milieu produced during an infection may modify the response against an irrelevant antigen and (ii) isotype switching may be influenced by the cytokine environment of a bystander immune response, even though the specific antigen-driven cytokine production is not modified. Thus, the isotypic profile is not always an absolute reflection of the cytokines produced by antigen-specific Th cells.

A Phase I clinical trial of immunotherapy with interferon-gamma gene-modified autologous melanoma cells: monitoring the humoral immune response

BACKGROUND

Tumor cells transduced with cytokine genes provide immunogenic vaccines for cancer immunotherapy.

METHODS

A Phase I clinical trial was conducted for the specific active immunization of melanoma patients with interferon-gamma (IFN-gamma) gene-modified autologous melanoma tumor cells. Short term melanoma cultures were transduced retrovirally with the gene for human IFN-gamma. The genetically modified melanoma cells secreted biologically active IFN-gamma and showed enhanced expression of major histocompatibility complex class I and class II surface antigens. These cells were inactivated by irradiation (50 gray) and were cryopreserved for the vaccine. Twenty melanoma patients were enrolled in this clinical trial. The immunizations were administered in escalating doses once every 2 weeks for 3 months. The first and second injections consisted of 2 million cells, followed by 6 million for the third and fourth injections, and then 18 million for the fifth and sixth injections. The humoral immune responses of the patients were assessed by enzyme-linked immunoadsorbent assay, radioimmunoassay, and radioimmunoprecipitation.

RESULTS

Thirteen of the 20 patients completed the immunization protocol. Eight of these 13 patients showed a humoral immunoglobulin (Ig)G response against autologous and allogeneic melanoma cells. The other five patients either had no detectable antimelanoma antibodies or showed a weak IgG response that did not rise significantly above the preimmune level. All the sera contained low or undetectable levels of antimelanoma IgM antibodies. The IgG response increased progressively in titer during the course of immunization. The positive sera showed preferentially strong binding to melanoma cell lines and some cross-reactivity to nonmelanoma tumors. A 75-80 kD antigen on melanoma cells was immunoprecipitated by postimmune sera of 3 of the responding patients. Preimmune sera from these three patients and sera from other patients immunized with a standard nontransduced melanoma cell vaccine failed to precipitate this antigen. Two patients with significant increases in serum IgG had clinical tumor regression, and two additional patients with low serum IgG response had transient shrinkage of nodular disease during therapy.

CONCLUSIONS

These data suggest that gene therapy with IFN-gamma-transduced melanoma cells is safe and worthy of further investigation in patients with less advanced stage malignant melanoma. The ability to monitor changes in the humoral responses of the immunized patients has been demonstrated.

The intensity of T cell receptor engagement determines the cytokine pattern of human allergen-specific T helper cells

Enhanced production of T helper (Th)2 cytokines by allergen-specific Th cells plays a major role in the induction and maintenance of IgE-mediated allergic disorders. The mechanism that triggers this type of response in atopic individuals is not fully understood. Allergen-specific human Th cell clones produce interleukin (IL)-4 and low or undetectable levels of interferon (IFN)-gamma after stimulation with low concentrations of antigen. However, these Th cell clones are capable of generating significant amounts of IFN-gamma after optimal activation through their T cell receptor (TcR). Allergen-specific Th cell clones isolated from allergic individuals required higher doses of antigen to reach the plateau of proliferation and to generate Th0 cytokine responses than their counterparts isolated from nonallergic subjects. On the other hand, if allergen was replaced by anti-CD3 monoclonal antibody (mAb), both allergic and nonallergic Th cell clones attained the highest level of proliferation and significant IFN-gamma production in response to equivalent concentrations of anti-CD3 mAb. These results indicate that the strength of T cell ligation, which can be modulated by the availability of the TcR ligand, controls the balance of Thl/Th2 cytokines produced by memory Th cells in vitro. In the particular case of bee venom phospholipase A2, it is shown that the expression of allergen-specific surface Ig on antigen-presenting B cells has little influence on antigen uptake and therefore in determining the levels of T cell activation and cytokine production. Alternatively, the affinity of particular major histocompatibility complex class II molecules on antigen-presenting cells for allergen-derived peptides might determine the amount of specific ligand presented to the Th cells and play a decisive role skewing the Th cell cytokine production towards Th1 or Th2 phenotypes. These findings, which are consistent with the changes in cytokine patterns observed following clinical hyposensitization, suggest that polarized human Th2 cell subsets still retain the capacity to modulate their cytokine pattern.

Induction of donor specific transplantation tolerance to cardiac allografts following treatment with nondepleting (RIB 5/2) or depleting (OX-38) anti-CD4 mAb plus intrathymic or intravenous donor alloantigen

The nondepleting monoclonal antirat CD4 antibody, RIB 5/2, has been shown to modulate, but not eliminate, the CD4+ T cells and to prolong survival of rat skin, renal, or cardiac allografts when serially administered after transplantation. In the present study, we compared the efficacy of recipient pretreatment with a single dose of nondepleting RIB 5/2 or depleting OX-38 anti-CD4 monoclonal antibody plus donor alloantigen given intravenously or intrathymically 21 days before transplantation on the survival of completely MHC-mismatched rat cardiac allografts. Intraperitoneal injection of a single dose (20 mg/kg) of RIB 5/2 resulted in a decrease in CD4 surface molecule expression on peripheral CD4+ T cells without cell elimination as shown by FACS analysis. The nonspecific effect of a single dose of RIB 5/2 mAb had resolved by 21 days after treatment as evidenced by the almost complete recovery of normal surface CD4 molecule expression. Cardiac allografts transplanted immediately or 21 days after a single dose of RIB 5/2 alone were uniformly acutely rejected. On the other hand, recipients treated with depleting anti-CD4 OX-38 (20 mg/kg) acutely rejected cardiac allografts transplanted 21 days later, but indefinitely accepted all grafts transplanted on the same day. In contrast, combined treatment with i.v. donor splenocytes (25 x 10(6)) plus nondepleting RIB 5/2, but not with depleting anti-CD4 mAb, OX-38, resulted in survival for more than 100 days in 75% of recipients of donor specific, but not third party, cardiac allografts transplanted 21 days later. Irradiation (3000 rads) of the i.v. donor splenocytes combined with RIB 5/2 abrogated their tolerizing effect. When donor antigen was given intrathymically, both RIB 5/2 and OX-38 resulted in indefinite tolerance to cardiac allografts transplanted 21 days later. The failure of exogenous administration of high dose (180,000 IU/injection) rIL-2 for 10 days to reverse the unresponsiveness of i.v. SC plus RIB 5/2 pretreatment suggests that this tolerant state is not due to a deficiency of IL-2. In vitro studies showed marked inhibition of MLC responsiveness and cytolytic T cell activity in tolerant recipients that cannot be reversed by the addition of IL-2. Thus, pretransplant intravenous donor alloantigen combined with a dose of nondepleting anti-CD4 mAb, RIB 5/2, which alone has no significant effect, induced donor specific cardiac allograft tolerance.

Functional significance of polymorphism among MHC class II gene promoters

The functional significance of polymorphism among MHC class II promoters in man and mouse is here reviewed, mainly in terms of the hypothesis of differential expression. The hypothesis proposes that differences between antigen-presenting cells in MHC class II expression exert a co-dominant effect on the Th1-Th2 cytokine balance, such that class II molecules of one type come to control to a greater extent the production of one group of cytokines, and those of another type the production of the alternative group. The survey deals with the influence of signal strength and antigen-presenting cell type on T-cell subset differentiation; functional differences between MHC class II molecules not obviously related to determinant selection; disease protection mediated by HLA alleles; mechanisms possibly responsible for allotypic and isotypic bias; overdominance (heterozygous advantage) in selection for expression of class II alleles; MHC class II promoter structure and function; inter-locus and inter-allele variability within human MHC class II gene upstream regulatory regions; a comparison of these polymorphisms in mouse and man; read-out of class II promoter function; and a comparison with expression of MHC class I. We conclude that the evidence that this variation is functionally active (i.e. controls expression) is increasing, but is not yet compelling. The crucial test still to come, we suggest, is whether or not the biological effects attributable to this polymorphism will line up with molecular studies on expression.