Immune Effector Mechanisms Research Articles

Imaging in targeted delivery of therapy to cancer

We review the current status of imaging as applied to targeted therapy with particular focus on antibody-based therapeutics. Antibodies have high tumor specificity and can be engineered to optimize delivery to, and retention within, the tumor. Whole antibodies can activate natural immune effector mechanisms and can be conjugated to beta- and alpha-emitting radionuclides, toxins, enzymes, and nanoparticles for enhanced therapeutic effect. Imaging is central to the development of these agents and is used for patient selection, performing dosimetry and assessment of response. gamma- and positron-emitting radionuclides may be used to image the distribution of antibody-targeted therapeutics While some radionuclides such as iodine-131 emit both beta and gamma radiation and are therefore suitable for both imaging and therapy, others are more suited to imaging or therapy alone. Hence for radionuclide therapy of neuroendocrine tumors, patients can be selected for therapy on the basis of gamma-emitting indium-111-octreotide imaging and treated with beta-emitting yttrium-90-octreotate. Positron-emitting radionuclides can give greater sensitivity that gamma-emitters but only a single radionuclide can be imaged at one time and the range of radionuclides is more limited. The multiple options for antibody-based therapeutic molecules, imaging technologies and therapeutic scenarios mean that very large amounts of diverse data are being acquired. This can be most effectively shared and progress accelerated by use of common data standards for imaging, biological, and clinical data.

Rethinking the Pathogenesis of Asthma

Asthma research has focused primarily on allergic pathways on the basis that the majority of asthma is associated with atopy, the recruitment of the Th2-type T cell, the cytokines, and the chemokines that are released on exposure to allergens, and the IgE pathway. However, despite considerable investment by industry, targeting these pathways has not resulted in new treatments being developed beyond blockade of cysteinyl leukotrienes and IgE and improvements in inhaled corticosteroids and beta(2)-adrenoceptor bronchodilators. Increasingly, it is recognized that asthma is a heterogeneous disorder, and while important, allergen sensitization is only one component of the disease, with many other environmental and genetic factors playing a role. In addition, these factors act locally on a susceptible airway epithelium that is both structurally and functionally deficient. It may be worthwhile to focus on increasing the resilience of the airways to environmental insults in addition to improving strategies that modify adaptive immunity or suppress inflammation.

Immune effector mechanisms against schistosomiasis: looking for a chink in the parasite's armour

A recombinant antigen vaccine against Schistosoma mansoni remains elusive, in part because the parasite deploys complex defensive and offensive strategies to combat immune attack. Nevertheless, research on rodent and primate models has shown that schistosomes can be defeated when appropriate responses are elicited. Acquired protection appears to involve protracted inhibition of larval migration or key molecular processes at the adult surfaces, not rapid cytolytic killing mechanisms. A successful vaccine will likely require a cocktail of antigens rather than a single recombinant protein. In addition, ways need to be found of keeping the immune system on permanent alert, either to achieve adequate inhibition of protein function in adults, or because a trickle of incoming parasites does not amplify the secondary response.

Induction of lepromin reactivity in cured lepromatous leprosy patients: impaired chemokine response dissociates protective immunity from delayed type hypersensitivity

Delayed Type Hypersensitivity (DTH) and protective immunity are thought to be tightly linked. Remarkable similarity exists between their cellular and immune mechanisms. However, their dissociation is also well known. Here we investigate the immunological mechanisms relevant for their dissociation in a group of non-relapsing cured lepromatous leprosy (CLL) patients. In these patients, using lepromin reaction as a model system of DTH we report critical role of tissue chemokine response in synchronous manifestation of these linked phenomena. Results indicate elevation of the threshold of tissue chemokine induction thus dissociating DTH from protective immunity in lepromin -ive CLL patients. We also show that the DTH anergy in these subjects is not an absolute one but depends on the strength of the stimulus. Our data provide insights into the intricate relationship between DTH and immunity and highlight the persistent presence of effector immune mechanisms involving these two pathways in apparently unresponsive lepromatous leprosy patients.

The immune response to and immunomodulation byHymenolepis diminuta

Analyses of laboratory-based helminth-rodent model systems have been immensely useful in delineating the workings of the mammalian immune system. Investigations in the 1970s-1980s on the fate of the rat tapeworm, Hymenolepis diminuta, in rats and mice and the systemic and local responses evoked following infection have contributed directly to our knowledge of how permissive and non-permissive hosts respond to the challenge of infection with a helminth parasite. This convenient laboratory model system has, in the authors' opinion, regrettably received considerably less attention in recent years. With the goal of highlighting the utility of this model system, data is presented on: (1) the immune and enteric responses of rats and mice to infection with H. diminuta; (2) the ability of excretory or secretory products derived from H. diminuta to significantly reduce T cell and macrophage activation in vitro; and (3) how assessment of H. diminuta-rodent models can be used to identify immune effector or regulatory mechanisms that can be translated into novel treatments for inflammatory and autoimmune disorders.

Interleukin‐10 Promoter Polymorphisms Influence HIV‐1 Susceptibility and Primary HIV‐1 Pathogenesis

Interleukin (IL)-10 directly inhibits human immunodeficiency virus type 1 (HIV-1) replication, but it may also promote viral persistence by inactivation of effector immune mechanisms. Here, we show in an African cohort that individuals with genotypes associated with high IL-10 production at 2 promoter single-nucleotide polymorphisms (-1082 and -592) were less likely to become HIV-1 infected but had significantly higher median plasma viral loads during the acute phase (<or=3 months after infection). However, as the infection progressed, the association between genotype and median viral load was reversed. Thus, IL-10 may influence HIV-1 susceptibility and pathogenesis, but effects on the latter may differ according to the infection phase.

Novel peptide therapeutics for treatment of infections

As antibiotic resistance increases worldwide, there is an increasing pressure to develop novel classes of antimicrobial compounds to fight infectious disease. Peptide therapeutics represent a novel class of therapeutic agents. Some, such as cationic antimicrobial peptides and peptidoglycan recognition proteins, have been identified from studies of innate immune effector mechanisms, while others are completely novel compounds generated in biological systems. Currently, only selected cationic antimicrobial peptides have been licensed, and only for topical applications. However, research using new approaches to identify novel antimicrobial peptide therapeutics, and new approaches to delivery and improving stability, will result in an increased range of peptide therapeutics available in the clinic for broader applications.

Monoclonal islet cell surface antibody dependent cellular cytotoxicity mediated by rat splenocytes with the RIN cell line as target.

A new method is described for testing monoclonal islet cell surface antibodies for their ability to mediate cellular immune effector mechanisms (ADCC). For the first time an IgM mediated cellular cytotoxicity is demonstrated. By using the RIN cell line as target the method was reproducible and easy to perform. The significance of such definition of monoclonal ICSA's to experimental diabetes research is discussed.

Swimming against the current: genetic vaccination against Trypanosoma cruzi infection in mice

Vaccines have had an unquestionable impact on public health during the last century. The most likely reason for the success of vaccines is the robust protective properties of specific antibodies. However, antibodies exert a strong selective pressure and many microorganisms, such as the obligatory intracellular parasite Trypanosoma cruzi, have been selected to survive in their presence. Although the host develops a strong immune response to T. cruzi, they do not clear the infection and instead progress to the chronic phase of the disease. Parasite persistence during the chronic phase of infection is now considered the main factor contributing to the chronic symptoms of the disease. Based on this finding, containment of parasite growth and survival may be one method to avoid the immunopathology of the chronic phase. In this context, vaccinologists have looked over the past 20 years for other immune effector mechanisms that could eliminate these antibody-resistant pathogens. We and others have tested the hypothesis that non-antibody-mediated cellular immune responses (CD4+ Th1 and CD8+ Tc1 cells) to specific parasite antigens/genes expressed by T. cruzi could indeed be used for the purpose of vaccination. This hypothesis was confirmed in different mouse models, indicating a possible path for vaccine development.

Immune Complexes and Complement in Serum and Synovial Fluid of Rheumatoid Arthritis Patients

Immune Complexes and Complement in Serum and Synovial Fluid of Rheumatoid Arthritis PatientsRheumatoid arthritis (RA) is predominantly an intraarticular inflammatory and autoimmune disease that involves different autoantibodies and effector mechanisms. The aim of the study was to determine the utility of Circulating Immune Complexes (CIC) and complement components (C3c, C4) as possible markers for the disease activity in laboratory diagnostics. In a cross-section study 59 patients, according to the clinical criteria, were categorized into two groups: group with moderate (MA, n=24), and group with severe activity (SA, n=35) of RA. The concentration of CIC, C3c and C4 in sera (S) and synovial fluids (SF) was examined by an immunonephelometric method in both groups and compared with values in the control group (n=15) of patients with lesions of the menisci. Obtained results showed that there was no statistical significance in the values of C3c and C4, in both biological fluids, among all tested groups. Significant differences were found in the levels of CIC in both fluids, while testing the parameters (× ± SD, IU/mL) in the sera of groups with SA and MA of RA: 7.43 ± 13.40; 3.01 ± 2.92 (p&lt;0.05) and SF: 13.47 ± 21.1, 5.33 ± 7.53 (p&lt;0.001), respectively. These differences were higher between the group with SA and CG. Results for the concentrations of CIC were significantly higher in SF compared to sera: in the RA group with SA by 77% and group with MA by about 82%. These data could provide a confirmation of the hypothesis about local, intraarticular autoantibodies and subsequent CIC production. It can be concluded that the examination of CIC concentration in serum, and where it is possible in SF, is a useful marker of disease activity in RA patients, in contrast to the tested components of the complement. This statement does not exclude their consumption within immune effector mechanisms, but elicits the possibility that lower molecular fragments (C3d, C4d), as well as the novel activation products, could be better disease activity markers in RA patients.

Anti–cyclic citrullinated peptide antibodies from rheumatoid arthritis patients activate complement via both the classical and alternative pathways

It has been suggested that anti-citrullinated protein antibodies (ACPAs) play an important role in the pathogenesis of rheumatoid arthritis (RA). To exert their pathologic effects, ACPAs must recruit immune effector mechanisms such as activation of the complement system. Mouse models of RA have shown that, surprisingly, arthritogenic antibodies activate the alternative pathway of complement rather than the expected classical pathway. This study was undertaken to investigate whether human anti-cyclic citrullinated peptide (anti-CCP) antibodies activate the complement system in vitro and, if so, which pathways of complement activation are used. We set up novel assays to analyze complement activation by anti-CCP antibodies, using cyclic citrullinated peptide-coated plates, specific buffers, and normal and complement-deficient sera as a source of complement. Anti-CCP antibodies activated complement in a dose-dependent manner via the classical pathway of complement, and, surprisingly, via the alternative pathway of complement. The lectin pathway was not activated by anti-CCP antibodies. Complement activation proceeded in vitro up to the formation of the membrane attack complex, indicating that all activation steps, including the release of C5a, took place. Our findings indicate that anti-CCP antibodies activate the complement system in vitro via the classical and alternative pathways but not via the lectin pathway. These findings are relevant for the design of interventions aimed at inhibition of complement-mediated damage in RA.

Immune cell-mediated liver injury

Liver diseases represent an important cause of morbidity and mortality in the world. Death of hepatocytes and other hepatic cell types is a characteristic feature of several forms of liver injury such as cholestasis, viral hepatitis, drug- or toxin-induced injury, and alcohol-induced liver damage. Moreover, irrespectively of the reason, liver injury seems to be facilitated by similar immune effector mechanisms common to these various liver diseases. Indeed, common immune effector mechanisms may explain the high prevalence of cirrhosis and cancer development in most forms of liver disease. Improved understanding of the immune cell-mediated mechanisms involved in hepatocyte cell death could be beneficial for the development of common therapeutic strategies against different forms of liver diseases. In this review, we will discuss novel findings on the role of different immune cells in liver disease and immune cell-induced death executioner mechanisms involved in hepatocyte cell death.

Teladorsagia circumcincta in the sheep abomasum: defining the role of dendritic cells in T cell regulation and protective immunity

Parasitic nematodes of the small-ruminant gastrointestinal tract pose a problem worldwide. The impact of these pathogens is worsened by the emergence of anthelmintic resistance to all three available classes of drugs. In addition to causing considerable economic loss, these parasites are detrimental to the health and welfare of sheep and goats. Vaccination offers an alternative approach to drug-based control and a great deal of investment has gone into the investigation of protective antigens for some of these nematode species. However, attempts at vaccination are hindered by a lack of understanding of how best to promote protective immunity to nematode species, such as Teladorsagia circumcincta, which inhabits the abomasum of sheep. This situation contrasts with that in murine models of gastrointestinal nematode infection, where the basis of protective immunity is increasingly well understood. In this review, we discuss the current knowledge of the immune effector mechanisms elicited by T. circumcincta and consider the probable role of dendritic cells in the initiation of both effector and regulatory responses in the abomasum.

The protective role of antibody responses duringMycobacterium tuberculosisinfection

Tuberculosis (TB) caused by Mycobacterium tuberculosis (Mtb) is one of the most important infectious diseases globally. Immune effector mechanisms that lead to protection or development of clinical disease are not fully known. It is generally accepted that cell-mediated immunity (CMI) plays a pivotal role in controlling Mtb infection, whereas antibody responses are believed to have no protective role. This generalization is based mainly on early classical experiments that lacked standard protocols, and the T helper type 1 (Th1)/Th2 paradigm. According to the Th1/Th2 paradigm Th1 cells protect the host from intracellular pathogens, whereas Th2 cells protect form extracellular pathogens. During the last two decades, the Th1/Th2 paradigm has dominated not only our understanding of immunity to infectious pathogens but also our approach to vaccine design. However, the last few years have seen major discrepancies in this model. Convincing evidence for the protective role of antibodies against several intracellular pathogens has been established. Studies of B cell-deficient mice, severe combined immunodeficiency (SCID) mice, passive immunization using monoclonal (mAb) and polyclonal antibodies and immune responses against specific mycobacterial antigens in experimental animals reveal that, in addition to a significant immunomodulatory effect on CMI, antibodies play an essential protective role against mycobacterial infections. In this review, our current understanding of the essential role of antibodies during Mtb infections, limitations of the Th1/Th2 model and the unfolding interdependence and mutual regulatory relationships between the humoral and CMI will be presented and discussed.

Inflammation and biliary tract injury

Primary biliary cirrhosis, primary sclerosing cholangitis and biliary atresia are thought to be immune-mediated cholangiopathies, however, gaps in knowledge remain with regard to the immunopathogenesis of these diseases. In this review, we highlight recent investigations pertaining to the role of both innate and adaptive immunity in bile duct damage. In innate immunity, evidence is presented for the contribution of cholangiocyte toll-like receptor stimulation promoting the ongoing inflammatory response. Innate-like lymphocytes may also be critical in the early phases of small bile duct injury found in primary biliary cirrhosis. With regard to adaptive immunity, the role of specific gene deficiencies in the susceptibility to immune-mediated cholangiopathies is reviewed. Furthermore, recent work analyzing the effector mechanisms of adaptive immunity leading to bile duct epithelial apoptosis are outlined. Understanding the intricacies of the inflammatory mechanisms culminating in bile duct epithelial injury are crucial to the future development of therapies aimed at halting the ongoing biliary tract destruction found in immune-mediated cholangiopathies. A paucity of research studies on primary sclerosing cholangitis was noted in this review and future research efforts should focus on primary sclerosing cholangitis, in addition to primary biliary cirrhosis and biliary atresia.

Anaphylatoxin Signaling in Murine Glial Cells (134.58)

Abstract Autoimmune destruction of myelin in diseases of the CNS is known to involve several immune effector mechanisms, including complement. The brain is considered an immunoprivileged site and is protected by the blood brain barrier; however, it has been shown that complement proteins are produced locally by glial cells. It has been found that glia express receptors for anaphylatoxins, C3a and C5a. Currently, our lab is investigating the effect of anaphylatoxins on glial cell activation as well as their overall role in demyelination and remyelination pathology. To study the role of anaphylatoxins in vitro, our lab created novel adenoviral vectors to express murine C3a or C5a. To study the role of anaphylatoxin signaling in glia we treated murine astrocyte and microglial cells with C3a, C5a or both anaphylatoxins, then examined various downstream effects. Using Western blots, we found that MAPK pathway proteins, ERK1/2, were highly phosphorylated when microglia were stimulated with C5a, but not C3a. In contrast, ERK1/2 were not activated in astrocytes treated with either anaphylatoxin. Finally, C5a was able to induce chemtoaxis in J774 murine macrophages; however we did not see significant migration of primary astrocytes or BV-2 microglia. These studies suggest that anaphylatoxin signaling and/or the functional consequences of that signaling is differentially regulated in a cell-specific manner.

Zoledronic acid and interleukin-2 treatment improves immunocompetence in HIV-infected persons by activating Vγ9Vδ2 T cells

gammadelta T cells bearing the Vgamma9Vdelta2 T-cell receptor exert many antiviral effector functions in humans, including release of anti-HIV factors and direct cytotoxicity against virus-infected cells. Moreover, they are known to activate dendritic cells, improving antigen presentation function. After HIV infection, Vgamma9Vdelta2 T-cell number and reactivity are rapidly affected and they decrease upon disease progression. Bisphosphonate drugs such as zoledronic acid (Zol), used to treat bone diseases, have been shown to induce in vivo, in combination with interleukin-2, Vgamma9Vdelta2 T-cells' activation. The aim of this work was to verify whether the administration of Zol in combination with interleukin-2 in HIV-infected patients might improve Vgamma9Vdelta2 T-cell function, including immune adjuvancy mediated by gammadelta-dendritic cell cross-talk. In HIV patients naive to antiretroviral therapy, we analyzed the effect of combined Zol and interleukin-2 treatment, in comparison to Zol alone, on Vgamma9Vdelta2 T-cell number, maturation and function, on dendritic cell activation and on HIV-specific CD8 T-cell response. Zol and interleukin-2-combined treatment induced in-vivo Vgamma9Vdelta2 T-cell expansion and maturation. Paralleling Vgamma9Vdelta2 T-cell activation, increased dendritic cell maturation and HIV-specific CD8 T-cell responses were found. The specific modulation of Vgamma9Vdelta2 T-cell number and responsiveness after HIV infection may be at least transiently restored in vivo by Zol and interleukin-2 treatment. In this way, the immune effector mechanisms, secondary to Vgamma9Vdelta2 T-cell activation, were improved, suggesting a possible adjuvancy role of Zol and interleukin-2 treatment in restoring innate and specific competence in HIV-infected persons.

A Case for Innate Immune Effector Mechanisms as Contributors to Disease Resistance in SIV-Infected Sooty Mangabeys

Natural or experimental infection of the African sooty mangabey (SM) with the simian immunodeficiency virus (SIV) results in chronic high levels of virus replication but is associated with none of the debilitating immunopathology, including the marked CD4 T-cell depletion, persistent cell activation and acquired immunodeficiency, that afflicts non-natural hosts such as SIV-infected Asian rhesus macaques (RM) and HIV-infected humans. Although SIV-infected RM have served as important models of AIDS given their remarkably similar course of disease to HIV-infected humans, deciphering the immune mechanisms that enable SIV-infected SM to resist disease development despite high viremia has yet to be defined. Intense studies for the past two decades using these nonhuman primate models have been conducted with the hope that this will yield better insight into the pathogenesis of AIDS, translating into the development of therapeutic strategies for HIV-infected individuals such as but not limited to identifying correlates of protective immunity that can be harnessed for the preparation of effective vaccines. Although much has been reported about SIV-specific adaptive immune responses in both the natural and unnatural hosts of SIV, we submit that innate immunity may play a larger than previously appreciated role in SIV pathogenesis, in particular during the period of acute infection. The purpose of this review is to therefore highlight the recent advances that have been made in understanding innate immune responses in SIV-infected SM and to discuss the role(s) of the major innate immune cell lineages that potentially contribute to disease resistance in this non-human primate species.

Effect of interferon gamma and CD40 ligation on intracellular monocyte survival of nontypeable Haemophilus influenzae

Nontypeable Haemophilus influenzae (NTHi) is a mucosal pathogen that is a major cause of respiratory infection, including sinusitis, otitis media and bronchitis. This bacterium has evolved a number of mechanisms to facilitate its survival in the human host. Recently it has been recognized that it is capable of intracellular survival in monocytes/macrophages and epithelial cells. Previous work by the authors has demonstrated that the protective response to NTHi is Th1 predominant. This information led to the hypothesis that the intracellular survival of NTHi in human monocytes may be reduced by two key effector mechanisms of Th1-mediated immunity: interferon gamma and ligation of CD40. This study assessed the effect of interferon gamma and ligation of CD40 on the intracellular survival of NTHi in human monocytes. Responses were studied in monocytes from subjects with bronchiectasis and persistent airway infection with NTHi and compared with control subjects. The results demonstrated that different isolates of NTHi were able to survive inside monocytes. Killing of one strain of NTHi could be enhanced by the addition of interferon gamma and CD40 ligation in both control and bronchiectasis subjects. Other strains were more resistant.

Permissive Conditions for Evolution of PNH Clones Are Characterized by Overproduction of IFN-γ by Clonal CD4 and CD8 T Cells, Fas-L by CTLs, and Promoted by Immunogenetic Background

The association between immune-mediated aplastic anemia (AA) and paroxysmal nocturnal hemoglobinuria (PNH) has been well documented, yet the related immune pathophysiology remains ill-defined. Response of AA patients with PNH clones to immunosuppressive agents such as anti-thymocyte globulin (ATG) and cyclosporine A provides clinical evidence for the involvement of the immune system in the evolution of PNH. The similar immunobiology of PNH and AA is also exemplified by the overrepresentation of HLA-DR*15 in AA, AA/PNH and PNH. To discern the relationship between T cell responses and effector mechanisms we applied a battery of immune tests to patients with these rare diseases. First, using T cell receptor Vβ flow cytometry in a cohort of patients with AA (N=42), AA/PNH (N=15), or PNH (N=18), we identified cytotoxic CD8 T cell (CTL) clonal expansions in 28/42 (66.7%), 9/15 (60%), and 7/18 (38.8%) patients, respectively. CD4 T cell expansions were present in 6/42 of AA (14.3%), 2/15 (13.3%) of AA/PNH, and 2/18 (11.1%) of PNH patients. We then studied whether expanded clones were associated with production of inflammatory cytokines; across the entire cohort, patients with clonal CD8 Vβ expansions demonstrated a significantly increased proportion of IFN-γ producing T cells as well as elevated levels of circulating Fas-L when compared to patients without clonal skewing (p=.032 CD4+IFN-γ+, p=.008 CD8+IFN-γ+, p=.097 sFAS-L). Even more pronounced was the increase in the proportion of IFN-γ producing CD4 T cells in patients with clonal CD4 Vβ expansions (p=.010). Furthermore, while a strong trend toward increased sFAS-L as detected by ELISA was found in patients with CD8 Vβ skewing vs. those without, patients with pronounced CD4 expansions did not produce elevated Fas-L levels, consistent with different effector mechanisms employed by CD4 vs. CD8 T cells. Based on these results we hypothesized that the presence of PNH clones will be associated with activation of immune effector mechanisms. Linear regression analysis of the size of the PNH clone vs. proportion of IFN-γ CTLs displayed a positive correlation that nearly reached statistical significance at α=0.05 (p=.067). A high proportion of CD4 IFN-γ cells (defined by a value above 95% mean confidence intervals of controls) was also associated with the presence of PNH (p=.048). Genetic analysis revealed further clues as to the increased propensity of patients with AA and PNH clones to produce elevated levels of IFN-γ; the hypersecretor genotype T/T for IFN-γ was over-represented in AA (28% vs. 10% in controls, p=.02) and correlated with presence of a PNH clone (35% vs. 14%, p=.01). An essential role of T cells in generating permissive conditions for the evolution of PNH clones is also supported by the immunogenetic relationship of PNH to HLA-DR*15, a relationship which was confirmed in our population of patients: phenotype frequency of HLA DR*15 was 42.8% AA, 40% AA/PNH, 27.8% PNH vs. 17.2% in control group. When HLA DR*15 positive and DR15 negative patients were compared, those with DR*15 displayed a strong trend toward increased proportion of CD8+IFN-γ producing cells (p=.094), previously shown to be elevated in patients with PNH clones. Our results reveal insights into the nature of permissive conditions involving oligoclonal T cell responses, oversecretion of proinflammatory cytokines, and immunogenetic background which together may promote the expansion of PNH clones. Conversely, it remains possible that the cytotoxic milieu may be a result of an immune response directed against intrinsically abnormal PNH clones.