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The immune function of living bodies has gained attention in engineering applications in a variety of fields. The authors proposed an immune network based on the immune response and researched its application to pattern recognition. The TH cell (helper T cell) that recognizes antigens in the immune response possesses diversity in order to fight various antigens and the function called interaction that communicates mutual information for correctly recognizing the antigens. The TH cell function successfully performs self-defense against unknown antigens. This paper proposes an immune network with the TH cell function added to an immune network we previously proposed. Specifically, we modeled the interaction and diversity functions of the TH cell in the matching process between input patterns and memory patterns. The proposed immune network is applied to a pattern recognition system of the alphabet and compared to a conventional method by numerical simulations. The proposed immune network exhibits lower incorrect recognition and rejections, and further improvement in the recognition rate over a conventional immune network by employing the process modeling the TH cell function. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 88(10): 12–22, 2005; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/ecjc.20162 [ABSTRACT FROM AUTHOR]

Dendritic cells (DCs) show a Janus-like functional behavior. They help us by their orchestration of numerous immune responses to defend our body against invading pathogenic micro-organisms and also induce regulatory T cells to inhibit immune reactions against autoantigens as well as diverse harmless environmental antigens. However, DCs can also be of harm to us when misguided by their microenvironment as in allergic and autoimmune diseases or when DCs are targeted and exploited by microbes and cancer cells to evade the immune defense. This huge and diverse functional repertoire of DCs requires complex decision-making processes and the integration of multiple stimulatory and inhibitory signals. Although a given DC type has an extensive functionally plasticity, DCs are heterogeneous and individual DC subtypes are differentially distributed in tissues, express distinct sets of pattern recognition receptors and differ in their capacity to program naive T cells. With the help of transgenic mouse models and selective ablation of individual DC subtypes, we are just at the beginning of understanding the DC system in its complexity. Obtaining a more detailed knowledge of the DC system in mice and men holds strong promise for the successful induction of immunity and tolerance in therapeutic trials. This review presents the recent advances in the understanding of DC biology and discusses why and how DC can help and hurt us. [ABSTRACT FROM AUTHOR]

Infection by the gastroduodenal pathogen Helicobacter pylori elicits a complex immunologic response in the mucosa involving neutrophils, plasma cells, eosinophils, and lymphocytes, of which T cells are the principal orchestrators of immunity. While so-called classical T cells (e.g. T-helper cells) that are activated by peptide fragments presented on antigen-presenting cells have received much attention in H. pylori infection, there exists a diverse array of other T cell populations that are potentially important for the outcome of the ensuing immune response, some of which have not been extensively studied in H. pylori infection. Pathogen-specific regulatory T cells that control and prevent the development of immunopathology associated with H. pylori infection have been investigated, but these cells can also benefit the bacterium in helping to prolong the chronicity of the infection by suppressing protective immune responses. An overlooked T cell population, the more recently described Th17 cells, may play a role in H. pylori-induced inflammation, due to triggering responses that ultimately lead to the recruitment of polymorphs, including neutrophils. The so-called innate or unconventional T cells, that include two conserved T cell subsets expressing invariant antigen-specific receptors, the CD1d-restricted natural killer T cells which are activated by glycolipids, and the mucosal-associated invariant T cells which play a role in defense against orally acquired pathogens in the intestinal mucosa, have only begun to receive attention. A greater knowledge of the range of T cell responses induced by H. pylori is required for a deeper understanding of the pathogenesis of this bacterium and its ability to perpetuate chronic infection, and could reveal new strategies for therapeutic exploitation. [ABSTRACT FROM AUTHOR]

The plaque-forming antibody response of C57BL/6 mice to rabbit gamma globulin (RGG) decreases as a function of age. RGG in tolerogenic form induces tolerance of young mice but sensitizes older animals. If antigen is administered together with lipopolysaccharide, the age-dependent decline in immune responsiveness is not observed, nor are older animals sensitized by tolerogen. The age-dependent decline in immune responsiveness is due to a loss of T helper capacity; sensitization by tolerogen is attributable to a subpopulation of B cells which becomes sensitized by the tolerogen. Older animals, treated with tolerogen, show a degree of central tolerance of T cells and a relatively slight, age-dependent diminution in colchicine- or cyclophosphamide-sensitive precursors of suppressor cells. [ABSTRACT FROM AUTHOR]

The present experiments were undertaken to delineate the role of LD and SD antigens in terms of memory in cell-mediated immune response (CML), Using recombinants that differ for either the H-2K or H-2D determinants (SD-different) and other recombinants differing for the central region of H-2 (LD different), we have investigated this question. The results indicate that priming to SD determinants leads to a more rapid and higher response when cells are restimulated in vitro with either the same SD antigt-n alone or the same SD plus an LD antigen and tested on target cells that possess either the SD antigen alone or both the LD and SD antigens. Antigens in the central regions of H-2, which includes LD, serve as the stimulus both for the helper T cells and for the c)'totoxic T lymphocjtes. Priming with a high dose of LD antigt-ns leads to memory in the cytotoxic T lymphocyte recognizing the cytotoxic target antigens coded by the central region of H-2. Nevertheless, memory could not be detected when priming was done under the same conditions as for SD antigens. Moreover, a primed helper T-cell response does not facilitate the development of increased CML on restimulation in vitro with the LD antigen used for priming and a new SD antigen. Thus, it seems that memory in CML is in the cytotoxic T lymphocyte and not in the proliferating helper cells. [ABSTRACT FROM AUTHOR]