Adaptive Immune Response PDF 2024

Adaptive immune response Dr Zahraa A Mohammed 2024  Objectives of this lecture 1- what are the components of adaptive immunity? 2- what are the properties of adaptive immunity? 3- what are the types of adaptive immunity? Overview of Innat the immune system Immu A...

Adaptive immune response Dr Zahraa A Mohammed 2024  Objectives of this lecture 1- what are the components of adaptive immunity? 2- what are the properties of adaptive immunity? 3- what are the types of adaptive immunity? Overview of Innat the immune system Immu Adapt e ive (nons ne pecifi syste (spec c) m ific) 2 nd Cellul1 Hum Cellul Hum st ar line oral ar line oral comp of comp comp of comp onent defen defen onent onent onent s se s s se s  Adaptive Immunity It is a specific immunity and consists of a collection of specialized organs, tissues, and cells. The cells of the specific immune system are able to recognize the presence of a pathogen in a much more efficient way than the innate immunity The characteristics of adaptive immunity are exquisite antigenic specificity and the ability to remember different types of antigens Adaptive immunity is activated only against invading foreign and never against its own molecules. The adaptive immune response take some days and weeks to be finished and constitutes the second line of the host defense. Furthermore, they develop the immune memory to the invading pathogen. The cells of the adaptive immune system are: 1- Lymphocytes (T cells and B cells) and plasma cells (end cells of B- lymphocyte differentiation). 2- Antigen-presenting cells (APCs)( Macrophages, B cells, and dendritic cells).  Types of adaptive immune response There are two types of adaptive immune response: 1-Humoral immune response mediated by B lymphocytes that produce and secrete molecules called immunoglobulins. it deals with freely circulating or extracellular pathogen, antibodies in the blood plasma or lumph bind to these pathogen ad either destroy, neutolize, or opsonize them 2- cellular immune response, mediated by T lymphocytes aginst intracellular pathogen. antigens displayed by APCs on their surface or infected cells activate the Tcells Adaptive immune defenses have in common that they are: Specific for particular antigens and are specialized to provide the best protection. Diverse in their specificity. Enhance with each repeated exposure (express Immunologic memory). Capable of self/non-self recognition. Self-limiting. These features of adaptive immunity are designed to give the individual the best possible defense against disease. Specificity is required, along with memory to protect against persistent or recurrent challenge. Diversity is required to protect against the maximum number of potential pathogens. The ability to distinguish between invaders and one’s own cells and tissues (self versus non-self) is vital in inhibiting a response to one’s own cells (autoimmunity). Self-limitation allows the system to return to a basal resting state after a challenge to conserve energy and prepare for the challenge by new microbes.  Types of Acquired Immunity I. Naturally Acquired Immunity: Obtained in the course of daily life. A. Naturally Acquired Active Immunity: – Antigens or pathogens enter body naturally. – Body generates an immune response to antigens. – Immunity may be lifelong (chickenpox or mumps) or temporary (influenza or intestinal infections). B. Naturally Acquired Passive Immunity: – Antibodies pass from mother to fetus via placenta or breast feeding (colostrum). – No immune response to antigens. – Immunity is usually short-lived (weeks to months). – Protection until child’s immune system develops. II. Artificially Acquired Immunity: Obtained by receiving a vaccine or immune serum. 1. Artificially Acquired Active Immunity: – Antigens are introduced in vaccines (immunization). – Body generates an immune response to antigens. – Immunity can be lifelong (oral polio vaccine) or temporary (tetanus toxoid). 2. Artificially Acquired Passive Immunity: – Preformed antibodies (antiserum) are introduced into body by injection. Snake antivenom injection from horses or rabbits. – Immunity is short lived (half life three weeks). – Host immune system does not respond to antigens.  Antigenicity and immunogenicity Antigenicity: is defined as the property of a substance ( antigen) that allows it to react with the products of a specific immune response( antibody or T cell receptor).Antigen, a macromolecule, is not reconized as a whole by either B cell or Tcells. each lymphocye receptor binds to a small or restricted part of the antigen called antigenic determinnant or epitope Immunogenicity: is defined as the property of a substance( immunogen) that endows it with the capacity to provoke a specific immune response. There are a wide variety of features that largely determine immunogenicity. They include the following: 1) Foreignness: Generally, molecules recognized as “self” are not immunogenic; for immunogenicity to occur, molecules must be recognized as “nonself”. 2) Size: The most potent immunogens are usually large proteins. Molecules with MW less than 10,000 Dalton are weakly immunogenic, and very small ones (e.g. amino acids) are nonimmunogenic. Certain small mol.(e.g hapten) become immunogenic only when linked to a carrier protein. Haptens and carriers: Artificial antigen have used to examine the immune response. In particular, small antigenic determinants are covalently coupled to larger molecules carriers 3) Chemical and structural complexity: Proteins and polysaccharides are among the most potent immunogens. another example, amino acid homopolymers are less immunogenic than heteropolymers containing two to three different amino acids. 4) Genetic constitution of the host: Two strains of the same species of animal may respond differently to the same Ag. 5) Dosage, route, and timing of Ag administration : Since the degree of the immune response depends on the amount of antigen given, the immune response can be optimized by carefully defining the dosage (including number of doses), route of administration, and timing of adminstrtation (including intervals between doses).  It should be noted that it is possible to enhance the immunogenicity of a substance by combining it with adjuvant. Adjuvants are compounds that enhance the immune response when administrated with antigen, to produce higher antibody titers and prolonged production Aluminum hydroxide, an inert compound that absorb the immunogn, stimulates phagocytosis.