Nutrition, Immunity, and Infection

Philip C. Calder, Anil D. Kulkarni, Philip C. Calder, Anil D. Kulkarni

• Verlag: CRC Press
• Jahr: 2017
• ISBN:
  9781351645195
• Auflage: 1
• Thema: Medicina
• Thema: Nutrición, dietética y bariatría

Both nutrition deficiency and overnutrition can have a significant effect on the risk of infection. Nutrition, Immunity, and Infection focuses on the influence of diet on the immune system and how altering one's diet helps prevent and treat infections and chronic diseases. This book reviews basic immunology and discusses changes in immune function throughout the life course. It features comprehensive chapters on obesity and the role of immune cells in adipose tissue; undernutrition and malnutrition; infant immune maturation; pre- and probiotics; mechanisms of immune regulation by various vitamins and minerals; nutrition and the aging immune system; nutrition interactions with environmental stress; and immunity in the global health arena.

Nutrition, Immunity, and Infection describes the various roles of nutrients and other food constituents on immune function, host defense, and resistance to infection. It describes the impact of infection on nutritional status through a translational approach. Chapters bring together molecular, cellular, and experimental studies alongside human trials so that readers can assess both the evidence for the effects of the food component being discussed and the mechanisms underlying those effects. The impact of specific conditions including obesity, anorexia nervosa, and HIV infection is also considered.

Chapter authors are experts in nutrition, immunity, and infection from all around the globe, including Europe, Australia, Brazil, India, and the United States. This book is a valuable resource for nutrition scientists, food scientists, dietitians, health practitioners, and students interested in nutrition and immunity.

1 Introduction to the Immune System

Philip C. Calder and Gerald Sonnenfeld

CONTENTS

1.1 Introduction

1.2 Innate Immunity

1.2.1 Barriers

1.2.2 Pattern Recognition Receptors

1.2.3 Cellular Components of Innate Immunity

1.2.3.1 Neutrophils

1.2.3.2 Monocytes and Macrophages

1.2.3.3 Eosinophils

1.2.3.4 Basophils and Mast Cells

1.2.3.5 Natural Killer Cells

1.2.4 Soluble Factors Involved in Innate Immunity

1.2.4.1 Complement

1.2.4.2 Acute Phase Proteins

1.2.4.3 Cytokines

1.3 Adhesion Molecules and Chemokines

1.3.1 Adhesion Molecules

1.3.2 Chemokines

1.4 Adaptive Immunity

1.4.1 Overview

1.4.2 Antigen Presentation and Recognition by T-Lymphocytes

1.4.2.1 Class I and II MHC Molecules

1.4.2.2 HLA-Independent Presentation of Antigen

1.4.3 T-Lymphocytes

1.4.3.1 T-Cell Development

1.4.3.2 T-Cell–Antigen Receptor Complex

1.4.3.3 T-Cell Subpopulations

1.4.4 B-Lymphocytes

1.4.4.1 B-Cell Development

1.4.4.2 Establishing the B-Cell Repertoire

1.4.4.3 T-Cell-Dependent B-Cell Responses

1.4.4.4 T-Cell-Independent B-Cell Responses

1.5 Other Immune Cell Types

1.6 Lymphoid Tissue and Cellular Communication

1.7 Regulatory T-Cells and Immune Tolerance

Further Reading

1.1 INTRODUCTION

The immune system is concerned with defense of the host against pathogenic organisms. It consists of a complex network of molecules and cells that have precise roles. The immune response may be divided into innate (sometimes called natural) and adaptive (sometimes called acquired) components. The innate immune response is rapid and nonspecific; it uses receptors encoded in the germ line. In contrast, the adaptive immune response is slower to react and specific; it uses receptors that are generated by somatic DNA rearrangement. Cells involved in the innate response include various phagocytic cells (neutrophils, monocytes, and macrophages), inflammatory cells (basophils, mast cells, and eosinophils), and natural killer (NK) cells. Molecules involved in innate immunity include complement, acute-phase proteins, and cytokines. The barrier function is also part of the innate immune response. The adaptive response involves the binding of antigen to surface receptors of antigen-specific B- and T-lymphocytes (also called B- and T-cells) via an antigen presenting cell (APC) and the subsequent activation and proliferation of the B- or T-cell. In response to the activation, B-cells secrete antibodies; these are antigen-specific immunoglobulins (Ig). The key role of antibodies is to identify and aid in the destruction of extracellular microorganisms. T-cells help B-cells to produce antibodies, therefore participating in adaptive immune defense against extracellular microorganisms. T-cells also play a key role in adaptive immune defense against intracellular microorganisms either directly, for example by killing virally infected cells, or indirectly, through activation of macrophages. The innate and adaptive immune responses work together in an integrated way to effectively eliminate organisms, toxins, and allergens. This chapter will provide an overview of the components and activities of the immune system. Further detail may be found in any immunology textbook.

1.2 INNATE IMMUNITY

1.2.1 BARRIERS

Barriers form a part of innate immune defense by acting to exclude pathogens and toxins. Barriers include the skin and the gastrointestinal, respiratory, and genitourinary tracts. These provide a physical impediment to entry. However, there are additional barrier functions. An example is mucosal secretions, which can trap microorganisms, and the acidic pH of the stomach, which can kill many invading bacteria.

1.2.2 PATTERN RECOGNITION RECEPTORS

It is essential for the innate immune system to recognize pathogens. This is achieved through pattern recognition receptors (PRRs) that recognize molecular structures that are broadly shared by pathogens. Researchers term these structures pathogen-associated molecular patterns (PAMPs), but since they also exist on nonpathogenic organisms, they are more correctly described as microbial-associated molecular patterns (MAMPs). When PRRs recognize MAMPs, several signaling pathways are initiated to activate the first line of host defensive responses necessary for killing infectious microbes. In addition, PRR signaling induces maturation of dendritic cells (DCs), which are responsible for antigen processing and presentation, so initiating the second line of host defense, adaptive immunity.

Toll-like receptors (TLRs) were the first PRRs to be identified. They are expressed either on the cell surface or associated with intracellular vesicles (Figure 1.1). More than ten functional TLRs have been identified in humans. Each TLR detects distinct MAMPs derived from viruses, bacteria, mycobacteria, fungi, and parasites (Table 1.1). These include lipopolysaccharide (LPS) from gram-negative bacteria, peptidoglycan, lipoteichoic acid, bacterial flagellar proteins, viral double-stranded RNA, and unmethylated DNA with CpG motifs characteristic of microbial DNA. Other classes of cytosolic PRRs also exist, including RIG-I-like receptors (RLRs) and Nod-like receptors (NLRs).

FIGURE 1.1 Toll-like receptor (TLR) signaling. Individual TLRs initiate overlapping and distinct signaling pathways in various cell types such as macrophages, dendritic cells, and inflammatory monocytes. Engagement of TLRs with their ligands induces conformat...