Basic Immunology 2023/2024 PDF

Basic Immunology Dr. Hanan Hosny 2023 / 2024 Ass.Prof.Dr. Hanan Hosny  OBJECTIVES Innate Adaptive Immunity Passive and active immunity Antibodies and its types  IMMUNITY Definition: “The immune system distinguishes cells that belong within the...

Basic Immunology Dr. Hanan Hosny 2023 / 2024 Ass.Prof.Dr. Hanan Hosny  OBJECTIVES Innate Adaptive Immunity Passive and active immunity Antibodies and its types  IMMUNITY Definition: “The immune system distinguishes cells that belong within the body (self) from those that do not (nonself). ANTIGEN Definition: A substance (antigen) that is capable of inducing an immune response on the part of the host organism. A “self” component may be considered an antigen even though one does not generally make immune responses against those components.  EPITOPE: Small part of an antigen that interacts with an antibody; 10-12 amino acids Any given antigen may have several epitopes. Each epitope is recognized by a different antibody  ANTIBODIES Proteins that recognize and bind to a particular antigen with very high specificity. Made in response to exposure to the antigen. Each antibody has at least two identical sites that bind antigen: Antigen binding sites. It may be called immunoglobulins (Igs). Types of immunity: Innate (natural) immunity Early, rapid responses, but limited & „non-specifc” Phagocytes, macrophages, Adaptive (acquired) immunity Take time but powerful (slow first time) ‘specificity + memory’ Lymphocytes (B & T cells)  CHARACTERISTIC OF INNATE IMMUNITY 1- Does not need previous stimulation 2-Not specific 3-No memory 4- Limited Diversity  TYPES OF INNATE IMMUNITY) 1) Anatomical barriers (skin) 2) Mechanical: - Flushing action of tears - Nasal hairs induce in Respiratory tract 3)Biochemical: Non-specific (eg. Low pH in stomach)  Characteristics Examples/Cells Innate immunity -Responds rapidly Anatomical - No memory Mechanical - No specificity Physical barriers Phagocytes cells (PMNs and macrophages) Natural killer cells Adaptive immunity Responds Slowly T cells Memory B cells ( antibody) Highly specific  ADAPTIVE IMMUNE SYSTEM Definition: It is the ability of the body to modify the immune response on multiple occasions and develop memory. This one of the hallmarks distinguishing the adaptive from the innate immune system  ADAPTIVE IMMUNE SYSTEM 1st infection  memory  2nd infection slow response fast response -pathogen proliferate -pathogen killed -disease -no disease -symptoms -no symptom  THERE ARE TWO TYPES OF ADAPTIVE Passive immunity: occurs when antibodies are passed from one person to another. Active immunity involves two types of white blood cells - T-cells and B- cells, and it is the one which will develop immunity by his own system. Cells responsible for Adaptive immunity  LYMPHOCYTE 1-Lymphocytes are wholly responsible for the specific immune recognition of pathogens, so they initiate adaptive immune responses. 2.Lymphocytes are derived from bone-marrow stem cells. 3.B -lymphocytes mature in the bone marrow. T- lymphocytes mature in the thymus.  CELLS RESPONSIBLE FOR ADAPTIVE IMMUNITY: Cell- mediated immunity(T- cell) Humoral Immunity (B cell)  1-THE CELLULAR RESPONSE: It is carried by T- lymphocytes. The Major functions of T cells can be divided into two main categories: 1-Cytotoxic CD 8: is to lyse cells, kill infected ad cancer cells 2- T Hepler Cells CD 4: activation of memory B cells and cytotoxic cells Delayed hypersensitivity: is to release cytokines, therefore triggering an inflammatory response. The cellular immunity is against intracellular infections  2- THE HUMORAL RESPONSE: are antibodies produced in response to a given antigen from B- lymphocyte Effective against extracellular bacteria (most of bacteria) While its role against intracellular is limited  B CELLS work chiefly by secreting soluble substances known as antibodies (Ab) or Immunoglobulins, it will be called Plasma cell.  ANTIBODY(AB) BASIC STRUCTURE It is “y” shaped glycoprotein consists of a four-chain divided into :-two identical heavy (H) chains - two identical light chains linked by disulfide bonds.  ISOTYPES OF IMMUNOGLOBULIN - It has a variable region, give the antibody its specificity for binding antigen. -The variable region includes the ends of the light and heavy chains. - Heavy chain isotypes determine immunoglobulin isotype or class: ( lg M, lg D, l gG , lg A, and lg E  The amino acid sequence in the tips of the "Y" varies greatly among different antibodies. This variable region, composed of 110-130 amino acids, give the antibody its specificity for binding antigen. The constant region determines the mechanism used to destroy antigen.  ANTIBODY FUNCTIONS Ab bind to antigens to immobilize them, render them harmless "tag" the antigen for destruction and removal by other components of the immune system. Neutralization Phagocytosis Opsonization  IMMUNOGLOBULIN Primary immune response follow the first exposure to particular antigen will produce little immunoglobulin. The first Ig to be produced is Ig M, followed by Ig G This is very important in serological test of infectious disease; early we should test for IgM later we should test IgG.  IG M It is the first immunoglobulin to be formed following antigenic stimulation. lg M is effective at immobilizing antigen (agglutination). Activating the classical pathway of complement.  IG G make up the greatest amount of immunoglobulin 75%(most abundent) in the serum. Many lg G antibodies are effective in activating complement. opsonizing It can cross placenta  IG E It is present in relatively in low serum concentration Present on the surface of mast cells and eosinophils. Its activation allow the release of histamine and other inflammatory mediators, leading to immediate hypersensitivity (Allergic) responses.  IG A is known as secretory component. It is found in mucus, saliva, tears, breast milk, and gastrointestinal secretions. More lgA is produced daily than all the other Ig.