Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

The Theory of Island Biogeography

Pathogen Recognition and Innate Immunity

▪ Abstract The innate immune system is a universal and ancient form of host defense against infection. Innate immune recognition relies on a limited number of germline-encoded receptors. These receptors evolved to recognize conserved products of microbial metabolism produced by microbial pathogens, but not by the host. Recognition of these molecular structures allows the immune system to distinguish infectious nonself from noninfectious self. Toll-like receptors play a major role in pathogen recognition and initiation of inflammatory and immune responses. Stimulation of Toll-like receptors by microbial products leads to the activation of signaling pathways that result in the induction of antimicrobial genes and inflammatory cytokines. In addition, stimulation of Toll-like receptors triggers dendritic cell maturation and results in the induction of costimulatory molecules and increased antigen-presenting capacity. Thus, microbial recognition by Toll-like receptors helps to direct adaptive immune responses ...

/pdf/innate-immune-recognition-3eedeqyq83.pdf

Innate Immune Recognition

One of the mechanisms by which the innate immune system senses the invasion of pathogenic microorganisms is through the Toll-like receptors (TLRs), which recognize specific molecular patterns that are present in microbial components. Stimulation of different TLRs induces distinct patterns of gene expression, which not only leads to the activation of innate immunity but also instructs the development of antigen-specific acquired immunity. Here, we review the rapid progress that has recently improved our understanding of the molecular mechanisms that mediate TLR signalling.

Toll-like receptor signalling

Effector functions in the immune system are carried out by a variety of cell types, and as our understanding of the complexity of the system expands, the number of recognized subdivisions of cell types also continues to increase. B lymphocytes, producing antibody, were initially distinguished from T lymphocytes, which provide help for B cells (1, 2). The T-cell population was further divided when surface markers allowed separation of helper cells from cytotoxic cells (3). Although there were persistent reports of heterogeneity in the helper T-cell compartment (reviewed below), only relatively recently were distinct types of helper cells resolved. In this review we describe the differences between two types of cloned helper T cells, defined primarily by differences in the pattern of lymphokines ynthesized, and we also discuss the different functions of the two types of cells and their lymphokines. Patterns of lymphokine synthesis are convenient and explicit markers to describe T-cell subclass differences, and evidence increases that many of the functions of helper T cells are predicted by the functions of the lymphokines that they synthesize after activation by antigen and presenting cells. The separation of many mouse helper T-cell clones into these two distinct types is now well established, but their origin in normal T-cell populations is still not clear. Further divisions of helper T cells may have to be recognized before a complete picture of helper T-cell function can be obtained.

TH1 and TH2 cells: different patterns of lymphokine secretion lead to different functional properties.

On the intrathymic intercellular transfer of self-determinants

In vitro cultivation of nonlymphoid thymic cells: morphological and immunological characterization.

The effect of x-irradiation on T and B cells involved in an in vivo adoptive anti-hapten antibody response has been studied. In vitro x-irradiation inactivates both B cells and T cells. B cells are somewhat more sensitive than T cells to such treatment, the dose required to reduce B cell activity by 50% being about 50 R, whereas 200 R will reduce helper cell activity by 50%. By contrast, if recipient mice are primed with carrier, they develop helper activity that is totally resistant to 500 R x-irradiation within 3 days of immunization. This activity can not be transferred from irradiated, carrier-primed mice by either spleen cells or serum, although anti-carrier antibody is shown to give a modest helper effect late after boosting. However, this radioresistant helper effect can be reproduced in a cell transfer system by giving carrier-primed spleen cells to normal recipients that are then x-irradiated (500 R) and given a large dose of carrier protein. Neither cells nor carrier alone will give rise to such radioresistant helper effects. Similar helper activity is occasionally observed when normal mice are irradiated 24 hr after being given helper cells, in the absence of carrier, and boosted shortly thereafter. The differences between these radioresistant helper effects, and the radiosensitivity of helper cells transferred after x-irradiation, may be related to x-ray induced changes in cell migration patterns.

Charles A. Janeway

Papers

On the intrathymic intercellular transfer of self-determinants

In vitro cultivation of nonlymphoid thymic cells: morphological and immunological characterization.

Cellular cooperation during in vivo anti-hapten antibody responses. II. The effect of in vivo and in vitro x-irradiation on T and B cells.

T-cell development: a role for self-peptides in positive selection.

It is easier for a camel to pass the needle's eye.