specific and nonspecific immunity pdf

Specific and nonspecific immunity pdf

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Introduction

Contributors and Attributions

Specific and Non-Specific Natural Killer Cell Responses to Viral Infection

Introduction

The immune response is how your body recognizes and defends itself against bacteria, viruses, and substances that appear foreign and harmful. The immune system protects the body from possibly harmful substances by recognizing and responding to antigens. Antigens are substances usually proteins on the surface of cells, viruses, fungi, or bacteria. Nonliving substances such as toxins , chemicals, drugs, and foreign particles such as a splinter can also be antigens.

Introduction

In Units we looked at microorganisms: how they replicate, why some are potentially more pathogenic than others, and how we can control them with antimicrobial agents.

Units 4 and 5 are devoted to the ways in which the body defends itself against microbes and other potentially harmful cells and molecules. The body has two immune systems: the innate immune system and the adaptive immune system. Unit 5 deals with innate immunity while Unit 6 will cover adaptive immunity.

Let's first briefly compare acquired and innate immunity. Innate immunity is an antigen-nonspecific defense mechanisms that a host uses immediately or within several hours after exposure to almost any microbe. This is the immunity one is born with and is the initial response by the body to eliminate microbes and prevent infection. Innate immunity can be divided into immediate innate immunity and early induced innate immunity.

Immediate innate immunity begins 0 - 4 hours after exposure to an infectious agent and involves the action of soluble preformed antimicrobial molecules that circulate in the blood, our found in extracellular tissue fluids, and are secreted by epithelial cells.

These include:. These preformed innate defense molecules will be discussed in greater detail later in this unit. Early induced innate immunity begins 4 - 96 hours after exposure to an infectious agent and involves the recruitment of defense cells as a result of pathogen-associated molecular patterns or PAMPS binding to pattern-recognition receptors or PRRs.

These recruited defense cells include:. Unlike adaptive immunity, innate immunity does not recognize every possible antigen. Instead, it is designed to recognize molecules shared by groups of related microbes that are essential for the survival of those organisms and are not found associated with mammalian cells.

These unique microbial molecules are called pathogen-associated molecular patterns or PAMPS and include LPS from the gram-negative cell wall, peptidoglycan and lipotechoic acids from the gram-positive cell wall, the sugar mannose a terminal sugar common in microbial glycolipids and glycoproteins but rare in those of humans , bacterial and viral unmethylated CpG DNA, bacterial flagellin, the amino acid N-formylmethionine found in bacterial proteins, double-stranded and single-stranded RNA from viruses, and glucans from fungal cell walls.

In addition, unique molecules displayed on stressed, injured, infected, or transformed human cells also act as PAMPS. Because all microbes, not just pathogenic microbes, possess PAMPs, pathogen-associated molecular patterns are sometimes referred to as microbe-associated molecular patterns or MAMPs. Pathogen-associated molecular patterns can also be recognized by a series of soluble pattern-recognition receptors in the blood that function as opsonins and initiate the complement pathways.

In all, the innate immune system is thought to recognize approximately 10 3 of these microbial molecular patterns. Examples of innate immunity include anatomical barriers, mechanical removal, bacterial antagonism, antigen-nonspecific defense chemicals, the complement pathways, phagocytosis, inflammation, fever, and the acute-phase response.

In this current unit we will look at each of these in greater detail. Adaptive acquired immunity refers to antigen-specific defense mechanisms that take several days to become protective and are designed to react with and remove a specific antigen. This is the immunity one develops throughout life. During adaptive immunity, antigens are transported to lymphoid organs where they are recognized by naive B-lymphocytes and T-lymphocytes. These activated B- and T-lymphocytes subsequently proliferate and differentiate into effector cells.

An antigen is defined as a substance that reacts with antibody molecules and antigen receptors on lymphocytes. An immunogen is an antigen that is recognized by the body as nonself and stimulates an adaptive immune response. For simplicity we will use the term antigen when referring to both antigens and immunogens.

The actual portions or fragments of an antigen that react with antibodies and lymphocyte receptors are called epitopes. As we will see later in Unit 5, the body recognizes an antigen as foreign when epitopes of that antigen bind to B-lymphocytes and T-lymphocytes by means of epitope-specific receptor molecules having a shape complementary to that of the epitope. The epitope receptor on the surface of a B-lymphocyte is called a B-cell receptor and is actually an antibody molecule.

It is estimated that the human body has the ability to recognize 10 7 or more different epitopes and make up to 10 9 different antibodies, each with a unique specificity. In order to recognize this immense number of different epitopes, the body produces 10 7 or more distinct clones of both B-lymphocytes and T-lymphocytes, each with a unique B-cell receptor or T-cell receptor.

Among this large variety of B-cell receptors and T-cell receptors there is bound to be at least one that has an epitope-binding site able to fit, at least to some degree, any antigen the immune system eventually encounters. With the adaptive immune responses, the body is able to recognize any conceivable antigen it may eventually encounter. The downside to the specificity of adaptive immunity is that only a few B-cells and T-cells in the body recognize any one epitope. These few cells then must rapidly proliferate in order to produce enough cells to mount an effective immune response against that particular epitope, and that typically takes several days.

During this time the pathogen could be causing considerable harm, and that is why innate immunity is also essential. Flash animation showing epitopes reacting with specific B-cell receptor on a B-lymphocytes. Adaptive immunity usually improves upon repeated exposure to a given infection and involves the following:. Acquired immunity includes both humoral immunity and cell-mediated immunity and will be the topic of Unit 6.

Compare and contrast how innate immunity and adaptive immunity are typically initiated in response to microbes. We will now take a closer look at innate immunity.

Learning Objectives Compare adaptive acquired immunity with innate immunity. Compare immediate innate immunity with early induced innate immunity. Innate immunity Innate immunity is an antigen-nonspecific defense mechanisms that a host uses immediately or within several hours after exposure to almost any microbe. These include: antimicrobial enzymes and peptides; complement system proteins; and anatomical barriers to infection, mechanical removal of microbes, and bacterial antagonism by normal body microbiota These preformed innate defense molecules will be discussed in greater detail later in this unit.

These recruited defense cells include: phagocytic cells: leukocytes such as neutrophils, eosinophils, and monocytes; tissue phagocytic cells in the tissue such as macrophages ; cells that release inflammatory mediators: inflammatory cells in the tissue such as macrophages and mast cells ; leukocytes such as basophils and eosinophils; and natural killer cells NK cells.

For More Information: Leukocytes from Unit 5. Adaptive acquired immunity Adaptive acquired immunity refers to antigen-specific defense mechanisms that take several days to become protective and are designed to react with and remove a specific antigen. For More Information: Antibodies from Unit 6. Flash animation showing epitopes reacting with a specific TCR on a T8-lymphocyte. Adaptive immunity usually improves upon repeated exposure to a given infection and involves the following: antigen-presenting cells APCs such as macrophages and dendritic cells ; the activation and proliferation of antigen-specific B-lymphocytes ; the activation and proliferation of antigen-specific T-lymphocytes ; and the production of antibody molecules , cytotoxic T-lymphocytes CTLs , activated macrophages , and cytokines.

Summary The body has two immune systems: the innate immune system and the adaptive immune system. Innate immunity is the immunity one is born with and is the initial response by the body to eliminate microbes and prevent infection. Immediate innate immunity begins 0 - 4 hours after exposure to an infectious agent and involves the action of soluble preformed antimicrobial molecules that circulate in the blood and in extracellular tissue fluids.

Adaptive immunity is the immunity one develops throughout life. Contributors and Attributions Dr.

Contributors and Attributions

We live in a sea of infectious agents, and we have evolved several mechanisms for protecting ourselves against those that are potentially pathogenic. There are several simple physical and chemical barriers that constitute and important first line of defense. Our skin provides a highly effective barrier to infectious agents despite the fact that skin is colonized by an impressive array of microbial agents. Injury to the skin abrasions, cuts, incisions, burns, etc. Given the effectiveness of intact skin, our major vulnerabilities are:.


individual pathogens in customized ways. Human Anatomy & Physiology: Body Defense & Immunity; Ziser Lecture Notes, 3. Nonspecific Immunity.


Specific and Non-Specific Natural Killer Cell Responses to Viral Infection

What happen if foreign invader attack the body to the second time in innate immunity? How innate immunity will response? An Ag can specifically bind to an Ab molecule. An Ag i. The term Ag, is used for a molecule i.

As mentioned in Unit 5, the body has two immune systems: innate immunity and adaptive immunity. Unit 5 dealt with innate immunity. In Unit 6 we will cover adaptive immunity. Let's first again briefly compare acquired and innate immunity. Innate immunity is an antigen-nonspecific defense mechanisms that a host uses immediately or within several hours after exposure to almost any microbe.

Immune system

Our present understanding of the functioning and evolutionary history of invertebrate innate immunity derives mostly from studies on a few model species belonging to ecdysozoa.

Introduction

Initially identified by their ability to kill tumor cells without prior sensitization of the host, natural killer NK cells are now known to provide a crucial initial defense against pathological organisms. In particular, they play a critical role during the early phases of infection days 0 to 5 while specific immunity develops reviewed in [1]. Recent advances, however, indicate that NK cells specifically recognize virus-infected cells in a manner akin to their recognition of tumor cells, and also respond non-specifically to viral infections.

In Units we looked at microorganisms: how they replicate, why some are potentially more pathogenic than others, and how we can control them with antimicrobial agents. Units 4 and 5 are devoted to the ways in which the body defends itself against microbes and other potentially harmful cells and molecules. The body has two immune systems: the innate immune system and the adaptive immune system. Unit 5 deals with innate immunity while Unit 6 will cover adaptive immunity.

Difference between Innate and Adaptive Immunity

Information

The interrelations between nonspecific and specific mechanisms for maintaining immune homeostasis, the mechanisms for induction, regulation, and possibilities for targeted immune correction are discussed. Immunity is the capability of multicellular organisms to resist harmful microorganisms from entering it. Immunity involves both specific and nonspecific components. The nonspecific components act as barriers or eliminators of a wide range of pathogens irrespective of their antigenic make-up. Other components of the immune system adapt themselves to each new disease encountered and can generate pathogen-specific immunity. An immune system may contain innate and adaptive components.

NCBI Bookshelf. Autoimmunity: From Bench to Bedside [Internet]. The innate immune response is the first mechanism for host defense found in all multicellular organisms. The innate immune system is more ancient than the acquired or adaptive immune response, and it has developed and evolved to protect the host from the surrounding environment in which a variety of toxins and infectious agents including bacteria, fungi, viruses and parasites are found 1. The immune system is complex and is divided in two categories: i the innate or nonspecific immunity, which consists of the activation and participation of preexistent mechanisms including the natural barriers skin and mucosa and secretions; and ii the adaptive or specific immunity, which is targeted against a previously recognized specific microorganism or antigen. Thus, when a given pathogen is new to the host, it is initially recognized by the innate immune system and then the adaptive immune response is activated 2.

Nonspecific Defense Mechanisms and Specific Immune Protection of Trout Against Viral Agents

В Третьем узле виднелось голубоватое сияние: терминалы по-прежнему работали; они обеспечивали функционирование ТРАНСТЕКСТА, поэтому на них поступало аварийное питание. Сьюзан просунула в щель ногу в туфле Феррагамо и усилила нажим.

2 comments

  • Recotarvi 16.11.2020 at 20:23

    Immune system , the complex group of defense responses found in humans and other advanced vertebrates that helps repel disease-causing organisms pathogens.

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  • Tais Г. 21.11.2020 at 01:07

    PDF | Non specific immunity | Find, read and cite all the research you need on ResearchGate.

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