Interferon gamma derived from CD4(+) T cells is sufficient to mediate T helper cell type 1 development

Interferon gamma (IFN-gamma) has been implicated in T helper type 1 (Th1) cell development through its ability to optimize interleukin 12 (IL-12) production from macrophages and IL-12 receptor expression on activated T cells. Various systems have suggested a role for IFN-gamma derived from the innate immune system, particularly natural killer (NK) cells, in mediating Th1 differentiation in vivo. We tested this requirement by reconstituting T cell and IFN-gamma doubly deficient mice with wild-type CD4(+) T cells and challenging the mice with pathogens that elicited either minimal or robust IL-12 in vivo (Leishmania major or Listeria monocytogenes, respectively). Th1 cells developed under both conditions, and this was unaffected by the presence or absence of IFN-gamma in non-T cells. Reconstitution with IFN-gamma-deficient CD4(+) T cells could not reestablish control over L. major, even in the presence of IFN-gamma from the NK compartment. These data demonstrate that activated T cells can maintain responsiveness to IL-12 through elaboration of endogenous IFN-gamma without requirement for an exogenous source of this cytokine.     

Association and direct activation of signal transducer and activator of transcription1alpha by platelet-derived growth factor receptor

The binding parameters of [3H]nociceptin were examined in membrane preparations of rat heart and compared with those of [3H]dynorphin A-(1-13) ([3H]Dyn A-(1-13)). Scatchard analysis of [3H]nociceptin binding revealed the presence of two distinct sites: a high affinity (Kd: 583 nM) low capacity (Bmax: 132 pmol/mg protein) site and a low affinity (Kd: 10,316 nM) high capacity (1552 pmol/mg protein) site. Dyn A and related peptides were potent competitors of the binding to the high affinity site with the following rank order of potency: alpha-neo-endorphin > Dyn A-(2-13) = Dyn A-(3-13) > Dyn A-(5-13) > Dyn A-(1-13) > Dyn A > Dyn B > Dyn A-(6-10) > Dyn A-(1-8). Nociceptin was 6.7 times less potent than Dyn A with a Ki of 4.8 microM as compared with 0.72 microM for Dyn A. The order of potency of the various peptides in inhibiting [3H]nociceptin binding correlated well (r = 0.93) with their ability to complete with the binding of [3H]Dyn A-(1-13) (Dumont and Lemaire, 1993). In addition, the high affinity [3H]nociceptin and non-opioid [3H]Dyn A-(1-13) sites were both sensitive to NaCl (120 mM) and the phospholipase C (PLC) inhibitors, U-73122 and neomycin (100 microM). The binding activities were less affected by the weak PLC inhibitor, U-73343, and no effect was observed with the non-hydrolysable GTP analogs. Gpp(NH)p and GTP-gamma-S. Nociceptin (1-50 microM) was also shown to inhibit the uptake of [3H]noradrenaline ([3H]NA) by cardiac synaptosomal preparations. In spontaneously hypertensive rats (SHR), the potency of nociceptin in inhibiting [3H]NA uptake was increased by 1.6-fold as compared with Wistar Kyoto (WKY) control rats and such effect was accompanied by comparable increased levels of cardiac ORL1 mRNA and [3H]nociceptin high affinity sites. These changes correlated well with the previously observed increased levels of non-opioid cardiac [3H]Dyn A-(1-13) sites in SHR (1.3 times as compared with WKY) and increased potency of Dyn A-(1-13) in inhibiting [3H]NA uptake by cardiac synaptosomes in SHR (2.2-fold as compared with WKY) (Dumont and Lemaire, 1995). The results demonstrate that in rat heart the characteristics of the high affinity, low capacity [3H]nociceptin binding site are similar to those of the non-opioid Dyn binding site. The stimulation of this site by nociceptin, Dyn A or related peptides is more likely to produce a modulation of PLC activity and [3H]NA uptake and may participate to the pathophysiology of hypertension.     

Murine leishmaniosis: a paradigm for the importance of T helper 1 and T helper 2 cells

The murine model of leishmaniosis is a prototypic example for the critical role played by T helper cells in immunity to pathogens. Cytokines, such as interleukin-12 and interleukin-4, are the major regulatory factors for differentiation of naive T helper cells into T helper 1 and T helper 2 cells, respectively. T helper 1 cells, which are cellular immune mechanisms involving gamma interferon production, are associated with protection against murine leishmaniosis. Loss of T helper 1 activity (i.e., reduced gamma interferon production and lack of macrophage activation) leads to a fatal progressive course of murine leishmaniosis. Knowledge of the murine model of leishmaniosis is now contributing to studies of infectious diseases in humans, livestock and companion animals. Greater insight into the pathogenesis, diagnosis and therapy of infectious diseases will be gained from the analysis of cytokine-dependent regulation of T helper responses during infection. In particular, the development of prophylactic and therapeutic vaccines will benefit significantly from these studies.     

Selective expression and functions of interleukin 18 receptor on T helper (Th) type 1 but not Th2 cells

OBJECTIVE: To evaluate tolerability and efficacy of combination therapy with methotrexate (MTX)/parenteral gold or MTX/other disease modifying antirheumatic drug (DMARD, d-penicillamine or chloroquine) in comparison with MTX monotherapy in patients with longstanding destructive active rheumatoid arthritis (RA). METHODS: In an open prospective trial all consecutive MTX-naive patients with active RA starting MTX treatment alone or in combination between January 1980 and December 1987, after failing one or more DMARD, were followed at regular intervals up to 108 months. Evaluations included the number of swollen joints (0-32), grip strength, patient assessment of pain and mobility, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and hemoglobin. Group 1, treated with MTX monotherapy (n = 97), was compared with Group 2, with combination therapy MTX/parenteral gold (n = 126) and Group 3 with MTX + other DMARD (n = 48). RESULTS: There were no significant differences between the groups in mean age (59/57/56 yrs), disease duration (9.6/7.7/8.3 yrs), seropositivity (80/88/82%), or ACR anatomical disease stage (2/3 in stage III and IV). The number of swollen joints (16.8/19.3/16.1 of 32) and the CRP (4.4/5.1/4.7 mg/dl) was significantly greater in Group 2; other disease activity variables were not significantly different. The mean MTX dose at baseline (mostly parenteral) was 16.8/17.0/12.8 mg and could be reduced to around 12 mg (predominantly oral) in the 3 groups. Frequency of adverse events (80/83/88%), nature of clinical (nausea, hair loss, stomatitis) and laboratory (liver enzyme elevation, slight proteinuria) side effects, and withdrawal rate for side effects (20.6/15.0/12.5%) were not significantly different between the groups. After 5 years 54/54/80% of patients continued their treatment. All efficacy variables improved significantly (p < 0.001) in all groups without significant intergroup difference. Improvement > 50% in the ESR was achieved in 63/68/41% and in the swollen joint count in 70/85/48% of patients after 3 years. The number of patients taking oral steroids decreased from 63/59/65% to 22/31/48% after 3 years. In half the patients hemoglobin increased by at least 1 g/dl. CONCLUSION: Combination therapy of MTX with parenteral gold or other DMARD is effective in reducing clinical and biochemical disease activity in patients with longstanding destructive RA with no greater risk of toxicity compared with MTX alone; our study however, did not show clear advantages of combination therapy versus monotherapy for effectiveness.     

Activated T helper 1 and T helper 2 cells differentially express the beta-2-adrenergic receptor: a mechanism for selective modulation of T helper 1 cell cytokine production

We recently reported that resting clones of murine Th1 cells, but not resting Th2 cells, expressed a detectable level of the beta-2-adrenergic receptor (beta 2AR). In the present study, we proposed that the level of beta 2AR expression on anti-CD3 mAb-activated CD4+ effector Th cells may differ from the level on resting cells, and that a change in receptor expression may alter the functional responsiveness of these cells to either the beta 2AR-selective ligand terbutaline or the sympathetic neurotransmitter norepinephrine. Following anti-CD3 activation, the beta 2AR was expressed on Th1 cells, but not Th2 cells. The number of binding sites on Th1 cells was maintained, with no change in affinity, over a 24-h activation period. When Th clones were exposed to terbutaline following anti-CD3 activation, Th1 cell, but not Th2 cell, cytokine production was modulated. IL-2 production by Th1 cells was decreased, while IFN-gamma production was not significantly altered. The decrease in IL-2 production was concentration dependent and was blocked by an antagonist. In comparison with control supernatants, the lower level of IL-2 present in terbutaline-exposed culture supernatants supported the proliferation of an IL-2-dependent Th1 clone to a lesser degree. Additionally, norepinephrine down-modulates IL-2, but not IFN-gamma, production by binding specifically to the beta-adrenergic receptor. Thus, a detectable level of the beta 2AR is expressed on activated Th1 cells, but not activated Th2 cells, thereby providing a mechanism by which IL-2 production is preferentially modulated by an endogenous and therapeutic ligand following Th1 cell activation.     

Interferon-gamma and interleukin-10 inhibit antigen presentation by Langerhans cells for T helper type 1 cells by suppressing their CD80 (B7-1) expression

CD80(B7-1) and CD86(B7-2) co-stimulatory molecules have been reported to activate Th1/Th2 development pathways differentially. It is well known that Langerhans cells (LC), potent antigen-presenting dendritic cells in the epidermis, express several co-stimulatory molecules and that this expression is modulated by several cytokines. Based on the recently reported effect of interferon (IFN)-gamma and interleukin (IL-)-10 on the expression of CD80 and CD86 by LC, we examined the effects of these cytokines on the expression of CD54 (intercellular adhesion molecule-1) and CD40 in addition to CD80 and CD86 on LC, and correlated the expression of each co-stimulatory molecule with antigen presentation for a Th1 clone by cultured LC (cLC) treated with these cytokines. LC cultured for 72 h significantly up-regulated MHC class II antigen expression and all the co-stimulatory molecules were examined. As previously reported, IL-10 or IFN-gamma inhibited the up-regulation of CD80 expression. Granulocyte/macrophage-colony-stimulating factor (GM-CSF) partially restored the suppression of CD80 expression induced by IFN-gamma on cultured LC, while it had virtually no effect on the inhibition induced by IL-10. Antigen presentation for the myoglobin-specific syngeneic Th1 clone by cLC, which were pre-incubated with these cytokines, correlated well with their CD80 expression. In addition, among the antibodies for CD80, CD86, CD28 or CD40, the suppression of the Th1 clone stimulation by LC was found to occur only with anti-CD80 and anti-CD28 antibodies. Finally, we studied the effects of IFN-gamma and IL-10 on GM-CSF production by epidermal keratinocytes (KC). We could show that only IFN-gamma, but not IL-10, suppressed GM-CSF production by KC. These findings suggest that both IFN-gamma and IL-10 suppress antigen presentation by LC for Th1 cells by suppressing their CD80 expression. The inhibitory effect of IFN-gamma on CD80 expression on LC appears to be partially mediated through the suppression of GM-CSF production by KC.     

CD28-independent induction of T helper cells and immunoglobulin class switches requires costimulation by the heat-stable antigen

It is well established that B7-CD28/CTLA4 interactions play an important role in the induction of T helper cells for T-dependent antibody responses. However, targeted mutation of CD28 does not significantly affect production of IgG and activation of CD4 T helper cells in response to infections by some viruses and nematode parasites. To test whether the CD28-independent induction of Ig class switches requires costimulation by the heat-stable antigen (HSA), we compared T helper cell induction and antibody response in mice deficient for either HSA, CD28, or both genes. We found that after immunization with KLH-DNP, mice deficient for both CD28 and HSA lack DNP-specific IgA and all subtypes of IgG. This deficiency corresponds to a reduced number of effector helper T cells that rapidly produce IL-2, IL-4, and IFN-gamma after in vitro stimulation with carrier antigen KLH. In contrast, priming of T helper cells and Ig class switch are normal in mice deficient with either HSA or CD28 alone. IgM responses are not affected by any of these targeted mutations. These results demonstrate that CD28-independent induction of T helper cells and Ig class-switches requires costimulation by the HSA.     

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.