Immunology and Serology Techniques PDF

Immunology and Serology Techniques MLIMSER503 Learning Objectives 1. Compare an immunogen and an antigen 2. Define the term immunology. 3. Explain the functions of the immune system. 4. Describe the first, second, and third lines of body defense against microbial diseases. 5. Compare...

Immunology and Serology Techniques MLIMSER503 Learning Objectives 1. Compare an immunogen and an antigen 2. Define the term immunology. 3. Explain the functions of the immune system. 4. Describe the first, second, and third lines of body defense against microbial diseases. 5. Compare innate and adaptive immunity. 6. Analyze a case study related to immunity.  Key Terms acquired immunity active immunity adaptive immune system allografts antibodies antigen autoimmune disorder cell-mediated immunity complement cytokines endogenous  Key Terms exogenous genome hematopoietic cells humoral-mediated immunity immunocompetent immunoglobulins immunology inflammation innate immune system innate resistance interleukins  Key Terms major histocompatibility complex (MHC) mononuclear phagocyte system nonself passive immunity pathogen-associated molecular patterns (PAMPs) pattern recognition receptors (PRRs) phagocytosis vaccination  WHAT IS IMMUNOLOGY? Immunology is defined as resistance to disease, specifically infectious disease. Immunology consists of the following: study of the molecules, cells, organs, and systems responsible for the recognition and disposal of foreign (nonself) material; how body components respond and interact; the desirable and undesirable consequences of immune interactions; and the ways in which the immune system can be advantageously manipulated to protect against or treat disease.  CELLS OF THE IMMUNE SYSTEM Cooperation is required for optimal functioning of the immune system. This cooperative interaction involves specific cellular elements, cell products, and nonlymphoid elements. Cells of the immune system consist of lymphocytes, specialized cells that capture and display microbial antigen, and effector cells that eliminate microbes.  CELLS OF THE IMMUNE SYSTEM The principal functions of the major cell types involved in the immune response are as follows: Specific recognition of antigens Capture of antigens for display to lymphocytes Elimination of antigens  CELLS OF THE IMMUNE SYSTEM The immune system also has nonspecific effector mechanisms that usually amplify the specific functions. Nonspecific components of the immune system include mononuclear phagocytes, polymorphonuclear leukocytes, and soluble factors (e.g., complement).  Role of the Immune System Defending the body against infections Recognizing and responding to foreign antigens Defending the body against the development of tumors  Role of the Immune System Undesirable consequences of immunity include allergy, rejection of a transplanted organ, or an autoimmune disorder, in which he body’s own tissues are attacked as if they were foreign. BODY DEFENSES: RESISTANCE TO MICROBIAL DISEASE First Line of Defense Before a pathogen can invade the human body, it must overcome the resistance provided by the body’s first line of defense. The first barrier to infection is unbroken skin and mucosal membrane surfaces. These surfaces are essential in forming a physical barrier to many microorganisms because this is where foreign materials usually first contact the host.  First Line of Defense Keratinization of the upper layer of the skin and the constant renewal of the skin’s epithelial cells, which repairs breaks in the skin, assist in the protective function of skin and mucosal membranes. In addition, the normal flora (microorganisms normally inhabiting the skin and membranes) deter penetration or facilitate elimination of foreign microorganisms from the body.  First Line of Defense Secretions are also an important component in the first line of defense against microbial invasion. Mucus adhering to the membranes of the nose and nasopharynx traps microorganisms, which can be expelled by coughing or sneezing. Sebum (oil) produced by the sebaceous glands of the skin and lactic acid in sweat both possess antimicrobial properties.  First Line of Defense The production of earwax protects the auditory canals from infectious disease. Secretions produced in the elimination of liquid and solid wastes (e.g., urinary and gastrointestinal processes) are important in physically removing potential pathogens from the body. The acidity and alkalinity of the fluids of the stomach and intestinal tract, as well as the acidity of the vagina, can destroy many potentially infectious microorganisms. Additional protection is provided to the respiratory tract by the constant motion of the cilia of the tubules.  First Line of Defense cont. In addition to the physical ability to wash away potential pathogens, tears and saliva also have chemical properties that defend the body. The enzyme lysozyme, which is found in tears and saliva, attacks and destroys the cell wall of susceptible bacteria, particularly certain gram-positive bacteria. Immunoglobulin A (IgA) antibody is another important protective substance in tears and saliva.  Second Line of Defense: Natural Immunity Natural immunity (inborn or innate resistance) is one of the ways that the body resists infection after microorganisms have penetrated the first line of defense. Acquired resistance, which specifically recognizes and selectively eliminates exogenous orendogenous agents.  Second Line of Defense: Natural Immunity cont. Natural immunity is characterized as a nonspecific mechanism. If a microorganism penetrates the skin or mucosal membranes, a second line of cellular and humoral defense mechanisms becomes operational. The elements of natural resistance include phagocytic cells, complement, and the acute inflammatory reaction.  Second Line of Defense: Natural Immunity cont. Detection of microbial pathogens is carried out by sentinel cells of the innate immune system located in tissues (macrophages and dendritic cells [DCs]) in close contact with the host’s natural environment or that are rapidly reunited to the site of infection (neutrophils).  Second Line of Defense: Natural Immunity cont. Despite their relative lack of specificity, these cellular components are essential because they are largely responsible for natural immunity to many environmental microorganisms. These phagocytic cells, which engulf invading foreign material, constitute major cellular components. Tissue damage produced by infectious or other agents results in inflammation, a series of biochemical and cellular changes that facilitate phagocytosis (engulfment and destruction) of microorganisms or damaged cells  Second Line of Defense: Natural Immunity cont. If the degree of inflammation is sufficiently extensive, it is accompanied by an increase in the plasma concentration of acutephase proteins or reactants, a group of glycoproteins. Acute-phase proteins are sensitive indicators of the presence of inflammatory disease and are especially useful in monitoring such conditions.  Second Line of Defense: Natural Immunity cont. Complement proteins are the major humoral (fluid) component of natural immunity. Other substances of the humoral component include lysozymes and interferon, sometimes described as natural antibiotics. Interferon is a family of proteins produced rapidly by many cells in response to viral infection; it blocks the replication of virus in other cells.  Second Line of Defense: Natural Immunity cont. If a microorganism overwhelms the body’s natural resistance, a third line of defensive resistance exists. Acquired, or adaptive, immunity is a more recently evolved mechanism that allows the body to recognize, remember, and respond to a specific stimulus, an antigen. Adaptive immunity can result in the elimination of microorganisms and recovery from disease and the host often acquires a specific immunologic memory.  Third Line of Defense: Adaptive Immunity cont. This condition of memory or recall (acquired resistance) allows the host to respond more effectively if reinfection with the same microorganism occurs. Adaptive immunity, is composed of cellular and humoral components. The major cellular component of acquired immunity is the lymphocyte , the major humoral component is the antibody. Lymphocytes selectively respond to nonself materials (antigens), which leads to immune memory and a permanently altered pattern of response or adaptation to the environment.  Third Line of Defense: Adaptive Immunity cont. Lymphocytes selectively respond to nonself materials (antigens), which leads to immune memory and a permanently altered pattern of response or adaptation to the environment. Most actions in the two categories of the adaptive response, humoral-mediated immunity and cell mediated immunity, are exerted by the interaction of antibody with complement and the phagocytic cells (natural immunity) and of T cells with macrophages.  Third Line of Defense: Adaptive Immunity cont. Humoral-Mediated Immunity If specific antibodies have been formed to antigenic stimulation, they are available to protect the body against foreign substances. The recognition of foreign substances and subsequent production of antibodies to these substances define immunity.  Third Line of Defense: Adaptive Immunity cont. Antibody Mediated immunity to infection can be acquired if the antibodies are formed by the host or if they are received from another source; these two types of acquired immunity are called active immunity and passive immunity, respectively.  Third Line of Defense: Adaptive Immunity cont. Active immunity can be acquired by natural exposure in response to an infection or natural series of infections, or through intentional injection of an antigen. The latter, vaccination, is an effective method of stimulating antibody production and memory (acquired resistance) without contracting the disease. Suspensions of antigenic materials used for immunization may be of animal or plant origin.  Third Line of Defense: Adaptive Immunity cont. vaccination, These products may consist of living suspensions of weak or attenuated cells or viruses, killed cells or viruses, or extracted bacterial products (e.g., altered and no longer poisonous toxoids used to immunize against diphtheria and tetanus).  Third Line of Defense: Adaptive Immunity cont. The selected agents should stimulate the production of antibodies without clinical signs and symptoms of disease in an immunocompetent host (host is able to recognize a foreign antigen and build specific antigen-directed antibodies) and result in permanent antigenic memory. Booster vaccinations may be needed in some cases to expand the pool of memory cells.  Third Line of Defense: Adaptive Immunity cont. Artificial passive immunity is achieved by the infusion of serum or plasma containing high concentrations of antibody or lymphocytes from an actively immunized individual. Passive immunity via pre-formed antibodies in serum provides immediate, temporary antibody protection against microorganisms (e.g., hepatitis A) by administering preformed antibodies. The recipient will benefit only temporarily from passive immunity for as long as the antibodies persist in the circulation. Immune antibodies are usually of the IgG type with a half-life of 23 days.  Third Line of Defense: Adaptive Immunity cont. The main strategies for cancer immunotherapy aim to provide antitumor effectors (T lymphocytes and antibodies) to patients. The purpose is to immunize patients actively against their own tumors and to stimulate the patient’s own antitumor immune responses.  Third Line of Defense: Adaptive Immunity cont. In addition, passive immunity can be acquired naturally by the fetus through the transfer of antibodies by the maternal placental circulation in utero during the last 3 months of pregnancy. Maternal antibodies are also transferred to the newborn after birth. The amount and specificity of maternal antibodies depend on the mother’s immune status to infectious diseases that she has experienced.  Third Line of Defense: Adaptive Immunity cont. Passively acquired immunity in newborns is only temporary because it starts to decrease after the first several weeks or months after birth. Breast milk, especially the thick yellowish milk (colostrum), produced for a few days after the birth of a baby is very rich in antibodies. However, for a newborn to have lasting protection, active immunity must occur.  Third Line of Defense: Adaptive Immunity cont. Cell-Mediated Immunity Cell-mediated immunity consists of immune activities that differ from antibody-mediated immunity. Lymphocytes are the unique bearers of immunologic specificity, which depends on their antigen receptors. The full development and expression of immune responses, however, require that nonlymphoid cells and molecules primarily act as amplifiers and modifiers.  Third Line of Defense: Adaptive Immunity cont. Cell-mediated immunity is moderated by the link between T lymphocytes and phagocytic cells (i.e., monocytes-macrophages). A B lymphocyte can probably respond to a native antigenic determinant of the appropriate fit. A T lymphocyte responds to antigens presented by other cells in the context of major histocompatibility complex (MHC) proteins.  Third Line of Defense: Adaptive Immunity cont. The T lymphocyte does not directly recognize the antigens of microorganisms or other living cells, such as allografts (tissue from a genetically different member of the same species, such as a human kidney), but recognizes when the antigen is present on the surface of an antigen-presenting cell (APC), the macrophage. APCs were at first thought to be limited to cells of the mononuclear phagocyte system. Recently, other types of cells (e.g., endothelial, glial) have been shown to possess the ability to present antigens.  Third Line of Defense: Adaptive Immunity cont. Lymphocytes are immunologically active through various types of direct cell-to-cell contact and by the production of soluble factors. Nonspecific soluble factors are made by or act on various elements of the immune system. These molecules are collectively called cytokines. Some mediators that act between leukocytes are called interleukins.  COMPARISON OF INNATE AND ADAPTIVE IMMUNITY Innate Immunity Adaptive Immunity Development Present Since Birth Develop after Birth Specificity Non-Specific Specific Response Time Fast, Immediate response Slow (3-5 days) response Potency Less Potent More Potent Inheritance Inherited No Inheritance Components Cellular and Humoral Cellular and Humoral Cells Neutrophils T-lymphocyte cells Mast cells B-lymphocyte cells Basophils Plasma cells Dendritic cells  Eosinophils Monocytes Macrophages Natural killer cells Humoral Complement Antibodies Lysozyme Cytokines Interferon Pathogen recognized by Pathogen recognized by receptors encoded in the receptors generated germline randomly Little or no memory of Memory of prior antigenic prior antigenic exposure exposure