Alun C. Kirby

Natural antibodies and complement are endogenous adjuvants for vaccine-induced CD8 + T-cell responses

CD8+ T cells are essential for long-term, vaccine-induced resistance against intracellular pathogens. Here we show that natural antibodies, acting in concert with complement, are endogenous adjuvants for the generation of protective CD8+ T cells after vaccination against visceral leishmaniasis. IL-4 was crucial for the priming of vaccine-specific CD8+ T cells, and we defined the primary source of IL-4 as a CD11b+CD11clo phagocyte. IL-4 secretion was not observed in antibody-deficient mice and could be reconstituted with serum from normal, but not Btk immune-deficient, mice. Similarly, no IL-4 response or CD8+ T-cell priming was seen in C1qa−/− mice. These results identify a new pathway by which immune complex–mediated complement activation can regulate T-cell-mediated immunity. We propose that this function of natural antibodies could be exploited when developing new vaccines for infectious diseases.

The innate immune response differs in primary and secondary Salmonella infection

This study examines innate immunity to oral Salmonella during primary infection and after secondary challenge of immune mice. Splenic NK and NKT cells plummeted early after primary infection, while neutrophils and macrophages (Mφ) increased 10- and 3-fold, respectively. In contrast, immune animals had only a modest reduction in NK cells, no loss of NKT cells, and a slight increase in phagocytes following secondary challenge. During primary infection, the dominant sources of IFN-γ were, unexpectedly, neutrophils and Mφ, the former having intracellular stores of IFN-γ that were released during infection. IFN-γ-producing phagocytes greatly outnumbered IFN-γ-producing NK cells, NKT cells, and T cells during the primary response. TNF-α production was also dominated by neutrophils and Mφ, which vastly outnumbered NKT cells producing this cytokine. Neither T cells nor NK cells produced TNF-α early during primary infection. The TNF-α response was reduced in a secondary response, but remained dominated by neutrophils and Mφ. Moreover, no significant IFN-γ production by Mφ was associated with the secondary response. Indeed, only NK1.1+ cells and T cells produced IFN-γ in these mice. These studies provide a coherent view of innate immunity to oral Salmonella infection, reveal novel sources of IFN-γ, and demonstrate that immune status influences the nature of the innate response.

Immunologic aspects of dermal and oral lichen planus : A review

There have been many investigations, both experimental and epidemiologic, of the forms of LP affecting the skin and oral mucosae. These studies have provided a varied range of hypotheses to explain not only the factors determining susceptibility to and onset of this disease, but also the immunologic mechanisms leading to the pathosis with which LP is associated. Much progress has been made, especially through in vitro studies, regarding detailed aspects of the immunology of LP. However, data is often conflicting or incomplete. In this review we attempt to bring together the currently available data regarding the immunologic basis of LP.

The potent bone-resorbing mediator of Actinobacillus actinomycetemcomitans is homologous to the molecular chaperone GroEL.

Actinobacillus actinomycetemcomitans is a Gram-negative bacterium implicated in the pathology of localized juvenile periodontitis, a condition involving rapid destruction of alveolar bone. We have established that gentle extraction of this bacterium in saline releases a proteinaceous fraction (which we have termed surface-associated material [SAM] which has potent osteolytic activity in the murine calvarial bone resorption assay. Fractionation of the SAM has now revealed that activity is associated with a 62-kD protein. This bone-resorbing activity can be blocked by a monoclonal antibody (raised to the whole bacterium) that is claimed to recognize a protein homologous to the Escherichia coli molecular chaperone GroEL. Purification of this bone-resorbing protein to homogeneity has been achieved by a combination of anion exchange, gel filtration, and ATP-affinity chromatography and the NH2-terminal sequence shows > 95% homology to E. coli GroEL. This GroEL homologue is found in the SAM of A. actinomycetemcomitans but is not found in the osteolytically active SAM from other Gram-negative or Gram-positive bacteria. The GroEL protein from E. coli, but not from Mycobacterium tuberculosis and Mycobacterium leprae, also showed activity in the bone resorption assay. We believe this to be the first observation that a molecular chaperone has the capacity to stimulate the breakdown of connective tissue.

Alveolar Macrophages Transport Pathogens to Lung Draining Lymph Nodes

The first step in inducing pulmonary adaptive immunity to allergens and airborne pathogens is Ag acquisition and transport to the lung draining lymph nodes (dLN). Dendritic cells (DC) sample the airways, and active transfer of Ag to the lung dLN is considered an exclusive property of migratory DC. However, alveolar macrophages (AM) are the first phagocytes to contact inhaled particulate matter. Although having well-defined immunoregulatory capabilities, AM are generally considered as restricted to the alveoli. We show that murine AM constitutively migrate from lung to dLN and that following exposure to Streptococcus pneumoniae, AM rapidly transport bacteria to this site. Thus AM, and not DC, appear responsible for the earliest delivery of these bacteria to secondary lymphoid tissue. The identification of this novel transport pathway has important consequences for our understanding of lung immunity and suggests more widespread roles for macrophages in the transport of Ags to lymphoid organs than previously appreciated.

Dynamic imaging of experimental Leishmania donovani-induced hepatic granulomas detects Kupffer cell-restricted antigen presentation to antigen-specific CD8+ T cells.

Kupffer cells (KCs) represent the major phagocytic population within the liver and provide an intracellular niche for the survival of a number of important human pathogens. Although KCs have been extensively studied in vitro, little is known of their in vivo response to infection and their capacity to directly interact with antigen-specific CD8+ T cells. Here, using a combination of approaches including whole mount and thin section confocal microscopy, adoptive cell transfer and intra-vital 2-photon microscopy, we demonstrate that KCs represent the only detectable population of mononuclear phagocytes within granulomas induced by Leishmania donovani infection that are capable of presenting parasite-derived peptide to effector CD8+ T cells. This restriction of antigen presentation to KCs within the Leishmania granuloma has important implications for the identification of new candidate vaccine antigens and for the design of novel immuno-therapeutic interventions.

CD11b Regulates Recruitment of Alveolar Macrophages but Not Pulmonary Dendritic Cells after Pneumococcal Challenge

Despite their close physical and functional relationships, alveolar macrophages (AMs) and pulmonary dendritic cells (pulDCs) have rarely been examined together in the context of infection. Using a nonlethal, resolving model of pneumonia caused by intranasal injection of Streptococcus pneumoniae, we demonstrate that AMs and pulDCs exhibit distinct characteristics during pulmonary inflammation. Recruitment of AMs and pulDCs occurred with different kinetics, and increased numbers of AMs resulted mainly from the appearance of a distinct subset of CD11b(High) AMs. Increased numbers of CD11b(High) and CD11b(Low) AMs, but not pulDCs, were recoverable from bronchoalveolar lavage fluid. CD11b expression on AMs was significantly increased by granulocyte-macrophage colony-stimulating factor but not by interleukin-10 or pathogen-associated stimuli. Finally, antibody blockade demonstrated that CD11b was critical for the recruitment of AMs, but not pulDCs, into the lung after pneumococcal challenge. These data demonstrate that there are significant differences between AM and pulDC responses to inflammatory pathogenic stimuli in vivo.

Differential Involvement of Dendritic Cell Subsets During Acute Salmonella Infection

Within murine CD11c+ dendritic cells (DC), CD8α+, CD8α−CD4+, and CD8α−CD4− subsets are defined. This study characterized the localization, number, and function of these subsets during acute Salmonella typhimurium infection. Immunohistochemical and flow cytometric analyses of spleens from mice orally infected with virulent S. typhimurium revealed that in situ redistribution and alteration in the absolute number and function of DC occurred in a subset-specific manner during infection. CD8α−CD4+ DC present at B cell follicle borders in the spleen of naive mice were absent 5 days post-Salmonella infection, despite no overall change in the absolute number of CD8α−CD4+ splenic DC. CD8α+ and CD8α−CD4− DC were prominently associated with the red pulp, and the frequency of these cells increased strikingly 5 days post-Salmonella infection. Significant quantitative increases in both CD8α+ and CD8α−CD4− subsets were associated with the in situ redistribution. Examination of Salmonella-infected TAP1−/−/β2-microglobulin−/− mice, which lack CD8α+ T cells, confirmed the differential subset-specific modulations in the DC populations both in situ and quantitatively. Ex vivo intracellular cytokine analysis showed significantly increased frequencies of CD8α+ DC producing TNF-α at days 2 and 5 postinfection. In contrast, CD4+ DC producing TNF-α were transiently increased followed by a significant reduction. No significant increase in IL-12p40 or IL-10 production by splenic DC was detected during the first 5 days post-S. typhimurium infection. Together these data reveal differential modulation of splenic DC subsets with regard to organization, number, and cytokine production during the course of acute Salmonella infection.

c-di-GMP is an Effective Immunomodulator and Vaccine Adjuvant Against Pneumococcal Infection

Cyclic diguanylate (c-di-GMP) is a unique bacterial intracellular signaling molecule capable of stimulating enhanced protective innate immunity against various bacterial infections. The effects of intranasal pretreatment with c-di-GMP, or intraperitoneal coadministration of c-di-GMP with the pneumolysin toxoid (PdB) or pneumococcal surface protein A (PspA) before pneumococcal challenge, were investigated in mice. We found that c-di-GMP had no significant direct short-term effect on the growth rate of Streptococcus pneumoniae either in vitro or in vivo. However, intranasal pretreatment of mice with c-di-GMP resulted in a significant decrease in bacterial load in lungs and blood after serotypes 2 and 3 challenge, and a significant decrease in lung titers after serotype 4 challenge. Potential cellular mediators of these enhanced protective responses were identified in lungs and draining lymph nodes. Intraperitoneal coadministration of c-di-GMP with PdB or PspA before challenge resulted in significantly higher antigen-specific antibody titers and increased survival of mice, compared to that obtained with alum adjuvant. These findings demonstrate that local or systemic c-di-GMP administration stimulates innate and adaptive immunity against invasive pneumococcal disease. We propose that c-di-GMP can be used as an effective broad spectrum immunomodulator and vaccine adjuvant to prevent infectious diseases.

Pulmonary dendritic cells and alveolar macrophages are regulated by γδ T cells during the resolution of S. pneumoniae-induced inflammation

γδ T cells commonly associate with mucosal and epithelial sites, fulfilling a variety of immunoregulatory functions. While lung γδ T cells have well‐characterized pro‐inflammatory activity, their potential role in the resolution of lung inflammation has yet to be explored in any detail. Indeed, given the importance of minimizing inflammation, the cellular mechanisms driving the resolution of lung inflammation are poorly understood. Using a murine model of acute Streptococcus pneumoniae‐mediated lung inflammation, we now show that resolution of inflammation following bacterial clearance is associated with a > 30‐fold increase in γδ T‐cell number. Although inflammation eventually resolves in TCRδ−/− mice, elevated numbers of alveolar macrophages and pulmonary dendritic cells, and the appearance of well‐formed granulomas in lungs of TCRδ−/− mice, together indicated a role for γδ T cells in regulating mononuclear phagocyte number. Ex vivo, both alveolar macrophages and pulmonary dendritic cells were susceptible to lung γδ T cell‐mediated cytotoxicity, the first demonstration of such activity against a dendritic cell population. These findings support a model whereby expansion of γδ T cells helps restore mononuclear phagocyte numbers to homeostatic levels, protecting the lung from the consequences of inappropriate inflammation. Copyright