Charles S. Via

Detection of three distinct patterns of T helper cell dysfunction in asymptomatic, human immunodeficiency virus-seropositive patients. Independence of CD4+ cell numbers and clinical staging.

We have tested the T helper cell (TH) potential of asymptomatic, HIV seropositive (HIV+) patients, using an in vitro assay for IL-2 production. Peripheral blood leukocytes (PBL) from 74 HIV+ patients and 70 HIV- control donors were tested for TH function when stimulated with influenza A virus (FLU), tetanus toxoid (TET), HLA alloantigens (ALLO), or PHA. Of the HIV+ patients, four different response patterns were observed: (a) patients who responded to all four stimuli (16%); (b) patients who were selectively unresponsive to FLU and TET, but responded to ALLO and PHA (54%); (c) patients who were unresponsive to FLU, TET, or ALLO, but responsive to PHA (16%); and (d) patients who failed to respond to any of these stimuli (14%). Our results indicate a time-dependent progression from a stage responsive to all four stimuli to a stage unresponsive to any of the stimuli tested, progressing in the order outlined above. The earliest TH defect is the loss of responses to FLU and TET, indicating a selective defect in CD4+ MHC self-restricted TH function. The later loss of ALLO and PHA IL-2 responses suggests more severe TH dysfunction involving both CD4+ and CD8+ T cells. None of these patterns of TH unresponsiveness in asymptomatic HIV+ individuals were correlated with CD4+ cell numbers nor with Walter Reed staging criteria. This study indicates that the in vitro TH assay used can detect multiple stages of immune dysregulation early in the course of HIV infection and raises the possibility that staging of HIV+ patients should include in vitro TH functional analyses of the type described here.

T-cell interactions in autoimmunity: insights from a murine model of graft-versus-host disease.

Abstract The response of F 1 hybrid mice to the injection of parental T cells depends upon, among other things, the genetic make up of donor and host. In most cases, inoculation results in the development of lethal graft-versus-host disease in the recipient, but under certain circumstances a condition resembling human lupus erythematosus ensues. According to Charles Via and Gene Shearer, an analysis of these lupus-inducing crosses suggests that disease is the result of a deficient cytotoxic T-cell response that is unable to control the proliferation of autoantibody-producing B cells. A better understanding of these murine model systems may allow the defects behind the human condition to be identified.

In Vivo Neutralization of TNF-α Promotes Humoral Autoimmunity by Preventing the Induction of CTL

Neutralization of TNF-α in humans with rheumatoid arthritis or Crohn’s disease has been associated with the development of humoral autoimmunity. To determine the effect of TNF-α neutralization on cell-mediated and humoral-mediated responses, we administered anti-TNF-α mAb to mice undergoing acute graft-vs-host disease (GVHD) using the parent-into-F1 model. In vivo neutralization of TNF-α blocked the lymphocytopenic features characteristic of acute GVHD and induced a lupus-like chronic GVHD phenotype (lymphoproliferation and autoantibody production). These effects resulted from complete inhibition of detectable antihost CTL activity and required the presence of anti-TNF-α mAb for the first 4 days after parental cell transfer, indicating that TNF-α plays a critical role in the induction of CTL. Moreover, an in vivo blockade of TNF-α preferentially inhibited the production of IFN-γ and blocked IFN-γ-dependent up-regulation of Fas; however, cytokines such as IL-10, IL-6, or IL-4 were not inhibited. These results suggest that a therapeutic TNF-α blockade may promote humoral autoimmunity by selectively inhibiting the induction of a CTL response that would normally suppress autoreactive B cells.

Role of perforin in controlling B-cell hyperactivity and humoral autoimmunity

To determine the role of perforin-mediated cytotoxic T lymphocyte (CTL) effector function in immune regulation, we studied a well-characterized mouse model of graft-versus-host disease (GVHD). Induction of acute GVHD using perforin-deficient donor T cells (pfp-->F1) initially resulted in features of acute GVHD, e.g., engraftment of both donor CD4(+) and CD8(+) T cells, upregulation of Fas and FasL, production of antihost CTL, and secretion of both Th1 and Th2 cytokines. Despite fully functional FasL activity, pfp donor cells failed to totally eliminate host B cells, and, by 4 weeks of disease, cytokine production in pfp-->F1 mice had polarized to a Th2 response. Pfp-->F1 mice eventually developed features of chronic GVHD, such as increased numbers of B cells, persistence of donor CD4 T cells, autoantibody production, and lupuslike renal disease. We conclude that in the setting of B- and T-cell activation, perforin plays an important immunoregulatory role in the prevention of humoral autoimmunity through the elimination of both autoreactive B cells and ag-specific T cells. Moreover, an ineffective initial CTL response can evolve into a persistent antibody-mediated response and, with it, the potential for sustained humoral autoimmunity.

In Vivo CD86 Blockade Inhibits CD4+ T Cell Activation, Whereas CD80 Blockade Potentiates CD8+ T Cell Activation and CTL Effector Function

To address whether a functional dichotomy exists between CD80 and CD86 in naive T cell activation in vivo, we administered anti-CD80 or CD86 blocking mAb alone or in combination to mice with parent-into-F1 graft-vs-host disease (GVHD). In this model, the injection of naive parental T cells into unirradiated F1 mice results in either a Th1 cytokine-driven, cell-mediated immune response (acute GVHD) or a Th2 cytokine-driven, Ab-mediated response (chronic GVHD) in the same F1 recipient. Combined CD80/CD86 blockade beginning at the time of donor cell transfer mimicked previous results seen with CTLA4Ig and completely abrogated either acute or chronic GVHD by preventing the activation and maturation of donor CD4+ T cells as measured by a block in acquisition of memory marker phenotype and cytokine production. Similar results were seen with selective CD86 blockade; however, the degree of CD4 inhibition was always less than that seen with combined CD80/CD86 blockade. A more striking effect was seen with selective CD80 blockade in that chronic GVHD was converted to acute GVHD. This effect was associated with the induction of Th1 cytokine production, donor CD8+ T cell activation, and development of antihost CTL. The similarity of this effect to that reported for selective CTLA4 blockade suggests that CD80 is a critical ligand for CTLA4 in mediating the down-regulation of Th1 responses and CD8+ T cell activation. In contrast, CD86 is critical for the activation of naive CD4+ T cells in either a Th1 or a Th2 cytokine-mediated response.

T Helper Cell Dysfunction in Systemic Lupus Erythematosus (SLE): Relation to Disease Activity

Patients with systemic lupus erythematosus (SLE) are known to have defects in both humoral and cellular immunity. The significance of defective T cell-mediated immunity and its relationship to disease activity have not been clearly established. We studiedin vitro T helper cell (Th) function in 150 SLE outpatients and correlated Th function with validated measures of disease activity. Interleukin 2 (IL-2) production by peripheral blood mononuclear cells (PBMC) was measured after stimulation with the recall antigens influenza A virus (FLU) and tetanus toxoid (TET), irradiated allogeneic peripheral blood mononuclear cells (ALLO), and phytohemagglutinin (PHA). We observed three patterns of Th response: (1) 76 of 150 (50%) of patients responded to the recall antigens FLU and/or TET, ALLO, and PHA; (2) 62 of 150 (42%) of patients did not respond to recall antigens but responded to ALLO and PHA; and (3) 12 of 150 (8%) of patients did not respond to either recall antigens or ALLO antigens. This diminished T cell function was correlated with higher disease activity as measured by four scales of clinical activity, such that individuals who exhibited morein vitro immune dysfunction presented with significant increases in their clinical activity indicies. The alterations in T cell function could not be accounted for by medication doses alone. Thus, SLE patients have multiple distinct defects at the level of the Th cell which are associated with clinical measures of disease activity.

Boswellia carterii Extract Inhibits TH1 Cytokines and Promotes TH2 Cytokines In Vitro

ABSTRACT Traditional herbal formulas used to treat inflammatory arthritis in China and India include Boswellia carterii or Boswellia serrata. They both contain boswellic acids (BAs) which have been shown to exhibit anti-inflammatory and antiarthritic properties. This study tests the hypothesis that mixtures of BAs derived from B. carterii have immunomodulatory properties. B. carterii plant resin obtained from China was prepared as an ethanol extract, and the presence of seven BAs was confirmed by column chromatography, high-performance liquid chromatography, and UV laser desorption/ionization tandem mass spectroscopy. The extract was then tested for its ability to alter in vitro production of TH1 cytokines (interleukin-2 [IL-2] and gamma interferon) and TH2 cytokines (IL-4 and IL-10) by murine splenocytes. Delivery of the resin extract using ethanol as a solvent resulted in significant cellular toxicity not seen with the addition of ethanol alone. By contrast, delivery of the resin extract using a sesame oil solvent resulted in a dose-dependent inhibition of TH1 cytokines coupled with a dose-dependent potentiation of TH2 cytokines. These results indicate that a purified mixture of BAs from B. carterii plant resin exhibits carrier-dependent immunomodulatory properties in vitro.

Differential Requirement for IFN-γ in CTL Maturation in Acute Murine Graft-versus-Host Disease

Although IFN-γ is the archetypal Th1 cytokine, its role in CTL maturation is uncertain. We used an in vivo mouse model of CTL development, parent-into-F1 acute graft-vs-host disease (AGVHD), to evaluate this issue. In AGVHD, transfer of naive parental T cells into F1 hosts stimulates the development of allospecific CTL effectors that eliminate host lymphocytes, particularly B cells. Complete elimination of IFN-γ, using IFN-γ-deficient donors and administering anti-IFN-γ mAb, suppressed B cell elimination, down-regulated ΤNF-α production, and enhanced Th2 cytokine production, but did not allow the B cell expansion characteristic of chronic GVHD (CGVHD). Because complete CTL inhibition results in full-blown CGVHD that is IFN-γ independent, these observations indicate that IFN-γ elimination only partially blocks CTL development. IFN-γ elimination did not inhibit donor T cell engraftment or activation in the AGVHD model, but almost completely blocked Fas/Fas ligand (FasL) gene expression, protein up-regulation, and Fas/FasL-mediated CTL killing. In contrast, IFN-γ elimination only partially inhibited perforin gene expression and perforin-mediated CTL activity. The contributions of IFN-γ to CTL development were indirect, because IFN-γ receptor-deficient donor cells differentiated normally into allospecific CTLs. Consistent with the view that the Fas/FasL and perforin pathways each mediate CTL killing in AGVHD, the absence of both perforin and IFN-γ (perforin knockout donor cells and anti-IFN-γ mAb) converted AGVHD to CGVHD. Thus, both IFN-γ-dependent induction of Fas/FasL and IFN-γ-independent induction of perforin contribute to CTL-mediated elimination of host B cells in AGVHD. Suppression of both pathways is required for typical CGVHD development.

Altered immunoregulation and autoimmune aspects of HIV infection: relevant murine models

After initial infection with human immunodeficiency virus 1 (HIV-1), patients may remain asymptomatic for years before the onset of acquired immune deficiency syndrome (AIDS). This non-aggressive or latent phase may be manifested by functional abnormalities of both T and B cells, even in the absence of critical reductions in lymphocyte numbers. At present, it is not clear whether the immune abnormalities in either the asymptomatic phase or in clinical AIDS are due solely to direct effects of HIV-1 or whether they also reflect host immunoregulatory mechanisms. In this article, by Charles Via, Herbert Morse and Gene Shearer, the immune abnormalities associated with early HIV-1 infection are compared with immune abnormalities found in three murine models of autoimmunity and immunodeficiency, and it is suggested that host mechanisms contribute to defective helper T (TH)-cell function early in the course of HIV-1 infection. Furthermore, two murine models appear relevant to the study of late HIV-1 infection and suggest a role for CD8+ T cells in the prevention of symptomatic AIDS.

The role of cytokines in the immunopathogenesis of lupus.

ConclusionsIncreasing data suggest that human and murine lupus are heterogeneous diseases and that, in genetically susceptible individuals, lupus may be the final common pathway of a number of etiological agents and/or immunological processes. This review has discussed a number of cytokines which appear to be involved in lupus pathogenesis. The models that we have put forward illustrate several possible mechanisms which may lead to lupus. During the next several years, the exact role of these cytokine in the pathogenesis of lupus should become more fully elucidated. Hopefully, this knowledge will provide the framework for newer, highly specific immunotherapeutic approaches to the treatment of this fascinating, complex, and potentially devastating disease.