On the origin of immunopathology.

Stranded between medicine and experimental biology, immunology is buried in its own problems and remains distant from important areas of current biology, such as evolutionary theory, developmental biology and cognitive sciences. Immunology has treated the living system merely as the place or dimension in which immune activity takes place, inserted on a misleading axis (progressive responsiveness versus no response; memory versus tolerance) which neglects the analysis of a robustly stable dynamics which is always present and is neither tolerance nor immunity-a problem currently approached as one of "regulatory" activity. However, a regulatory response also demands regulation, leading to an endless recursion and the adoption of a stimulus-response framework inevitably drives us away from the physiological processes in which lymphocytes are involved. Herein, we propose that immunological physiology, like everything else in the body is dynamic and conservative. Immunopathology, including inherited immunodeficiencies, severe forms of infectious diseases, allergy and autoimmune diseases, are interferences with this stability which frequently include oligoclonal expansions of T lymphocytes. We suggest that this decrease in clonal diversity results from a loss of the stabilizing connectivity among lymphocytes and are not simply markers of immunopathology, but are rather expressions of basic pathogenic mechanisms. The so-called autoimmune diseases are examples of this disequilibrium. In the last decade the characterization of an enormous and diversified commensal microbiota has posed a new and pressing problem: how to explain the harmonic conviviality with trillions of foreign macromolecules. In addition, robustly stable relations towards macromolecular diet can be established by simple ingestion, a state presently labeled as "oral tolerance", a problem that has been buffered for decades as anti-inflammatory protection of the gut. A major change in terminology is necessary to describe this new panorama. We focus on two important gaps in immunological discussions: (a) the organism, seen simultaneously as the medium with which the immune system is constantly in touch and as the entity that mediates the contact with external materials; and (b) the observer, the immunologist, who operates as a human being in human languaging with other human beings, and characterizes immunological specificity. We acknowledge that we are proposing radical departures from current dogma and that we should justify them. Most of what we propose stem form a way of seeing called Biology of Cognition and Language, that derives from ideas of the neurobiologist/philosopher Humberto Maturana, also known as "autopoiesis theory".

Indirect effects of oral tolerance improve wound healing in skin.

Tissue injury in adult mammalian skin frequently results in scarring while fetal mammalian skin heals with complete regeneration. Inflammatory reactions are among the factors thought to impair regeneration. Previous studies have shown that the injection of an immunologically tolerated protein blocks immune responses to unrelated antigens and is also able to inhibit inflammation in mice. This phenomenon, which we refer to as the indirect effects of oral tolerance, does not require the simultaneous injection of the tolerated antigen and the second antigen, and also occurs when the two antigens are given by separate routes of immunization. Herein, we investigated whether the i.p. injection of an orally tolerated antigen (ovalbumin, OVA) would inhibit inflammatory reactions at an incisional lesion and influence healing of adult mouse skin. In OVA-tolerant mice, the injection of OVA minutes before wounding altered inflammation: it reduced the numbers of mast cells, neutrophils, and lymphocytes but increased the number of macrophages around the lesion area. Tolerant mice also showed fewer myofibroblasts and reduced scar area. Furthermore, tolerant mice displayed a pattern of extracellular matrix deposition similar to that observed in intact skin, plus characteristics of regeneration, such as an increased deposition of fibronectin and tenascin-C. These observations suggest that the indirect effects of oral tolerance can alter the process of wound healing in skin and reduce scar formation.

Different requirements for the adoptive transfer of oral tolerance and its indirect effects assessed by DTH and antibody responses in mice.

Oral tolerance inhibits T-cell dependent reactions to antigens previously contacted by oral route. Parenteral re-exposure to orally-tolerated antigens inhibits immune responses to unrelated antigens, a phenomenon we have called "indirect effects" of oral tolerance. We examined the requirements of previous irradiation of C57BL/6 and BALB/c recipients to successful transfer of oral tolerance and its indirect effects using 1x10(8) splenocytes. When DTH reactions were evaluated, irradiation was not required to transfer both oral tolerance and its indirect effects. C57BL/6, but not BALB/c recipients, required irradiation to adopt suppressed antibody responses to tolerizing antigen. In BALB/c recipients, the indirect effect was transferred only if serum from the tolerant donors was added to the transferred splenocytes. CFSE labeled donor cells were not eliminated from non-irradiated C57BL/6, although unable to suppress antibody responses. Our results provide further evidences on the existence of a functional barrier in immunocompetent recipients that hinders the adoptive transfer of different immunological activities. Interactions between cells and serum components may be necessary to bypass this barrier.

Cell-mediated immune response to unrelated proteins and unspecific inflammation blocked by orally tolerated proteins.

Oral tolerance promotes a generalized decrease in specific immune responsiveness to proteins previously encountered via the oral route. In addition, parenteral immunization with a tolerated protein also triggers a significant reduction in the primary responsiveness to a second unrelated antigen. This is generally explained by 'innocent bystander suppression', suggesting that the transient and episodic effects of inhibitory cytokines released by contact with the tolerated antigen would block responses to the second antigen. In disagreement with this view, we have previously shown that: (i) these inhibitory effects do not require concomitance or contiguity of the injections of the two proteins; (ii) that intravenous or intragastric exposures to the tolerated antigen are not inhibitory; and (iii) that the inhibitory effect, once triggered, persists in the absence of further contact with the tolerated protein, possibly by inhibition of secondary responsiveness (immunological memory). The present work confirms that immunological memory of the second unrelated antigen is hindered by exposure to the tolerated antigen and, in addition, shows that this exposure: (i) inhibits the inflammation triggered by an unrelated antigen through the double effect of inhibiting production of leucocytes in the bone marrow and blocking their migration to inflammed sites; and (ii) significantly blocks footpaw swelling triggered by carrageenan. Taken together, these results conclusively demonstrate that inhibitory effects of parenteral injection of tolerated antigens are much more general than suggested by the 'innocent bystander suppression' hypothesis.

Dynamic stability in random and scale-free B-lymphocyte networks.

One of the most intriguing features of the immune system is regulation: a limited response when perturbed repeatedly. We propose a minimal network model for immune regulation in a lymphocyte network containing two types of elements: B lymphocytes and ligands that bind to their receptors. Effective interactions between B cells, mediated by other components of the immune system can be excitatory or inhibitory. In our model, B cell clones and ligand species are represented by nodes, and interactions by links. We expect that, as in many complex systems, the connectivity distribution is broad, motivating study of the model on a scale-free network; for comparison we study the same dynamics on a random graph. We characterize the dynamics of the model and its response to perturbations. Our model reproduces several key features of immune system dynamics: regulation (saturation of response), and more rapid response upon repeated perturbation with the same agents. Our results suggest that a scale-free network of interactions contributes to the regulation and dynamics of the immune system.

The conservative physiology of the immune system. A non-metaphoric approach to immunological activity.

Historically, immunology emerged as a biomedical science, concerned with host defense and production of anti-infectious vaccines. In the late 50s, selective theories were proposed and from then on, immunology has been based in a close association with the neo-Darwinian principles, such as random generation of variants (lymphocyte clones), selection by extrinsic factors (antigens) - and, more generally, on genetic determinism and functionalism. This association has had major consequences: (1) immunological jargon is full of "cognitive" metaphors, founded in the idea of "foreignness"; (2) the immune system is described with a random clonal origin, coupled to selection by random encounters; and (3) physiological events are virtually absent from immunological descriptions. In the present manuscript, we apply systemic notions to bring forth an explanation including systemic mechanisms able to generate immunological phenomena. We replace "randomness plus selection" and the notion of foreignness by a history of structural changes which are determined by the coherences of the system internal architecture at any given moment. The importance of this systemic way of seeing is that it explicitly attends to the organization that defines the immune system, within which it is possible to describe the conservative physiology of the immune system. Understanding immune physiology in a systemic way of seeing also suggests mechanisms underlying the origin of immunopathogeny and therefore suggests new insights to therapeutic approaches. However, if seriously acknowledged, this systemic/historic approach to immunology goes along with a global conceptual change which modifies virtually everything in the domain of biology, as suggested by Maturana.

Immunological activities are modulated by enteral administration of an elemental diet in mice.

BACKGROUND & AIMS: Elemental diets (EDs) have been used successfully in treatment of some intestinal inflammatory diseases; however, the mechanism that mediates their effects is still unclear. In this study we evaluated the immunological effect of enteral administration of an ED in mice. METHODS: C57BL/6 mice were fed an ED (El-Diet) from weaning up to adulthood and immunological parameters were analyzed. RESULTS: El-Diet-fed mice presented an underdeveloped gut-associated-lymphoid tissue with lower numbers of TCRalphabeta+IELs and lamina propria cells and low levels of secretory IgA when compared to chow-fed mice. They showed a systemic decrease in the production of IgG and IgA as well as a skewing towards a Th2 profile of cytokine production upon in vitro stimulation with an increase in IL-4 and a reduction in IFN-gamma and IL-6 secretion. CONCLUSION: Our study demonstrated the role of EDs in modulating immunological activities in mice and proposes a rational for their successful use in treatment of some intestinal inflammatory diseases.

Systemic effects of oral tolerance on inflammation: mobilization of lymphocytes and bone marrow eosinopoiesis.

Oral tolerance is a T-cell mediated phenomenon defined by inhibition of immune responsiveness to a protein previously contacted by the oral route. Oral tolerance may prevent autoimmune and allergic diseases that involve the recruitment and/or activation of different cell types including mast cells, neutrophils, eosinophils, monocytes and lymphocytes. The mechanisms by which oral tolerance avoids these immunological disorders are still controversial. Herein we used a murine model of ovalbumin (OVA)-induced peritonitis to investigate the effect of oral tolerance on allergic inflammation. Frequency of leucocyte subpopulations was evaluated by global and differential cell counts in peritoneal lavage fluid, peripheral blood, and bone marrow. Changes on lymphocyte subsets and adhesion molecules expression by these cells were analysed by flow cytometry. As compared with OVA-immune mice, intraperitoneal challenge of tolerant animals with OVA resulted in a significantly milder peritonitis, mostly affecting neutrophils and eosinophils; a concomitant reduction in total white blood cell counts was also observed, mainly because of lower neutrophil and eosinophil counts. Eosinophils, but not neutrophils, were also reduced in the bone-marrow of OVA-challenged tolerant mice. No changes occurred in total peritoneal lymphocyte counts in OVA-tolerant mice, however, there was a significant decrease in CD3+ CD8+ T cells and an increase in B cells (CD45R+) in these animals as compared to immune OVA-challenged animals. Altered expression of CD18 and CD54, respectively, in blood and peritoneal lymphocytes was also noted. These results suggest that, in addition to local specific effects, oral tolerance has systemic effects on the mobilization of leucocytes and bone-marrow eosinopoiesis.

Increased polyclonal immunoglobulin reactivity toward human and bacterial proteins is associated with clinical protection in human Plasmodium infection.

BACKGROUND: Polyclonal B-cell activation is well known to occur in Plasmodium infections, but its role in pathogenesis or protection remains unclear. However, protective properties of natural antibodies have previously been demonstrated in other contexts. METHODS: Sera from asymptomatic and symptomatic Plasmodium-infected subjects locally detected in a survey study in the Brazilian Amazon, and from unexposed and exposed but presently uninfected control subjects, were assayed by a standardized quantitative immunoblot method allowing simultaneous detection of IgG or IgM reactivity to a large number of parasite-unrelated proteins. RESULTS: In subjects free of coinfection with hepatitis B virus, IgG reactivity to human brain antigens and Escherichia coli proteins was strikingly enhanced in asymptomatic Plasmodium-infected individuals when compared to such with clinical malaria symptoms, or to uninfected control subjects. This difference was most characteristic for limited exposure times (less than ten years locally, or 20 years in endemic areas). It was more significant than a similar trend found for IgG to Plasmodium falciparum antigens, and unrelated to parasitaemia levels. Asymptomatic subjects with comparatively short exposure characteristically showed relatively elevated IgG versus IgM reactivity. Polyclonal IgG reactivity appears triggered by previous P. falciparum but not Plasmodium vivax malaria. CONCLUSION: The observed difference in polyclonal antibody production seems related to intrinsic activation states of infected individuals, rather than to parasite-antigen specific immune responses. However, it appears influenced by preceding stimuli. This supports the idea that acquired clinical immunity may not exclusively depend on antigen-specific responses, but also on the individual polyclonal reaction.

Natural immunoglobulins (contribution to a debate on biomedical education)

Immunology has contributed to biomedical education in many important ways since the creation of scientific medicine in the last quarter of the 19th century. Today, immunology is a major area of biomedical research. Nevertheless, there are many basic problems unresolved in immunological activities and phenomena. Solving these problems is probably necessary to devise predictable and safe ways to produce new vaccines, treat allergy and autoimmune diseases and perform safe transplants. This challenge involves not only technical developments but also changes in attitude, of which the most fundamental is to abandon the traditional stimulus-response perspective in favor of more "systemic" views. Describing immunological activities as the operation of a complex multi connected network, raises biological and epistemological issues not usually dealt with in biomedical education. Here we point to one example of systemic approaches. A new form of immunoblot (Panama blot), by which the reaction of natural immunoglobulins with complex protein mixtures may be analyzed by a special software and multivariate statistics, has been recently used to characterize human autoimmune diseases. Our preliminary data show that Panama blots can also be used to characterize global (systemic) immunological changes in chronic human parasitic diseases, such as malaria and schistosomiasis mansoni, that correlate with the clinical status

Assimilation, tolerance and the end of innocence

Immunological activity is conceptually and biochemically related to digestion and assimilation processes. Food materials comprise the vast majority of foreign macromolecules handled by the organism. Lympphocyte activation involves partial digestion ("processing") of both foreign and self molecules. Immunoglobulins accelerate the clearance (by opsonization) and intracellular digestion of materials to which they bind. Immunological activity may, therefore, be seen as a network of processes facilitating the assimilation of foreign materials. This same network is continuously incorporating new (emergent) cellular and molecular components into the lymphoid system. In oral tolerance, the organism is usually seen as becoming permissive to the presence of previously ingested antigens, as if their presence remained unacknowledged. However, the exposure of orally-tolerant animals to the tolerated antigens blocks the concomitant induction of unrelated immune responses. The assimilation of tolerated antigens to the network of lymphocyte activities, therefore, may have broad consequences. We claim that these "indirect effects"of the tolerated antigen cannot be ascribed to "innocent bystander"suppression, i.e. to fortuitous proximity to cells releasing suppressive cytokines.

Auto-imunidade como imunodeficiência / Autoimmunity as immunodeficiency

As doenças auto-imunes näo podem mais ser atribuídas à simples presença de clones linfocitários auto-reativos, porque esses clones podem ser encontrados em indivíduos sadios como componentes de redes idiotípicas normais. Por outro lado, sídromes similares ao lúpus eritematoso sistêmico (LES) podem ser induzidas em camundongos normais pela injeçäo de um idiotipo anti-DNA freqüentemente encontrado em pacientes de LES (16/6), que também é encontrado no soro normal. Em camundongos NZB/W, que desenvolvem espontaneamente uma síndrome lupóide, ocorrem taxas anormalmente elevadas da ativaçäo de um subtipo de linfócitos T (Th2), que podem ser responsáveis pela ativaçäo policlonal de linfócitos B, levando à produçäo de vários auto-anticorpos patogênicos. A encefalomielite alérgica experimental (EAE) pode ser induzida em camundongos pela injeçäo de clones de células T reativos com a proteína básica da mielina (MBP); pode também ser prevenida ou revertida, pela injeçäo de outros clones MBP-reativos. O processo fisiológico de ativaçäo de linfócitos T requer a apresentaçäo de peptídios ligados a produtos do MHC na membrana de linfócitos B ou de vários tipos de "células apresentadas". Há porém, exceçöes a essa regra. Interaçöes recíprocas diretas entre regiöes variáveis de receptores de linfócitos T e imunoglobulinas atuando como receptores em linfócitos B podem resultar na ativaçäo de ambas as células. Em doenças parasitárias crônicas, como a esquistossomose mansônica e a doença de Chagas, podem ocorrer idiotipos antiparasita capazes de ativar linfócitos T autólogos independentemente de processamento/apresentaçäo. Neste ensaio, sugerimos que o "pareamento independente" de linfócitos T e B, contornando a necessidade de processamento/apresentaçäo, pode ser importante na gênese de doenças auto-imunes e nas formas severas de parasitoses crônicas. A eficácia de injeçöes de imunoglobulinas normais poliespecíficas no tratamento de várias doenças auto-imunes também sugere que a restauraçäo da saúde resulta do restabelecimento de padröes normais de conectividade idiotípica

Aspectos cognitivos da atividade imunológica / Immunology: cognitive aspects

Tentamos aqui uma descriçäo concisa da natureza da atividade imunológica de acordo com três diferentes perspectivas: a perspectiva tradicional, dualista, de respostas eimunes específicas (o cognitivismo, o paradigma simbólico); uma perspectiva econexionista, ainda a ser completada pela adiçäo de "regras (definidas) de mudança" dos padröes de conectividade do sistema; e, uma terceira visäo, baseada na individualidade historicamente deteminada do sistema imune

Ordem e desordem: uma abordagem imunológica / Order and disorder: an immunological approach

A operaçäo do sistema imune (sua ordem) é criada pelo acoplamento de um processo (genético) especial de geraçäo de diversidade a um processo (ontogenético) de seleçäo positiva de linfócitos emergentes (sobrevivência associativa). Esta ordem deriva do próprio sistema, e constitui uma organizaçäo fechada que näo se modifica frente a contatos com materiais estranhos ao organismo (antígenos)