MLAB214 Basic And Clinical Immunology Fundamentals Of Immunology PDF

MLAB214 Basic and clinical immunology Chap 1- Overview and introduction to the Immune System An organ...

MLAB214 Basic and clinical immunology Chap 1- Overview and introduction to the Immune System An organ is made up of several types of tissue, including muscle tissue, fibrous tissue, and special cells Tissues are groups of cells that have a similar structure and act together to perform a specific function.There are four different types of tissues in animals: connective, muscle, nervous, and epithelial. In plants, tissues are divided into three types: vascular, ground, and epidermal. Groups of tissues make up organs in the body such as the brain and heart. Connective tissue connects or separates groups of other tissues.Muscle tissue comprises all the muscles in the body, and the specialized nature of the tissue is what allows muscles to contract. There are three types of muscle tissue: skeletal muscle, cardiac muscle, and smooth muscle. Skeletal muscle anchors tendons to bones and allows the body to move. Cardiac muscle is found in the heart and contracts to pump blood. Smooth muscle is found in the intestines, where it helps move food through the digestive tract, and it is also found in other organs like blood vessels, the uterus, and the bladder.Nervous tissue is found in the brain, spinal cord, and peripheral nerves, which are all parts of the nervous system. It is made up of neurons, which are nerve cells, and neuroglia, which are cells that help nerve impulses travel. Nervous tissue is grouped into four types: gray matter and white matter in the brain, and nerves and ganglia in the peripheral nervous system. The main difference between gray and white matter is that axons of the neurons in gray matter are unmyelinated, while white matter is myelinated. Myelin is a white, fatty substance that insulates neurons and is crucial for nervous system functioning. Stem cells are amazing cells that can transform into different types of cells in the body, such as blood, skin, nerve, or bone cells. There are different types of stem cells, depending on their source and potential. Embryonic stem cells are the most versatile, as they can become any cell type. Embryonic stem cells come from the blastocyst, a group of cells that forms a few days after fertilization. They are also called pluripotent stem cells, meaning many potentials. Adult stem cells are more specialized, as they only produce cells of a certain tissue or organ. They are also called tissue-specific stem cells or somatic stem cells. Some examples of adult stem cells are hematopoietic stem cells, which make blood cells; mesenchymal stem cells, which make bone, cartilage, and fat cells; and neural stem cells, which make brain cells. Stem cells have many applications in medicine, such as regenerating damaged tissues, treating diseases, and researching new therapies. They are also a source of ethical and scientific debate. Pluripotent stem cells: Embryonic stem cells and induced pluripotent stem cells. Non-embryonic or somatic stem cells: Commonly called “adult” stem cells. Totipotent stem cells: The most versatile and powerful, capable of differentiating into any cell type required for the development of a complete organism. Multipotent stem cells: Can differentiate into a limited range of cell types. Unipotent stem cells: Can only differentiate into one specific cell type An overview of the terminology is shown below, from earliest to final stage of development: [root]blast / pro[root]cyte / [root]cyte / meta[root]cyte /mature cell name HSCs are self-renewing cells: when they differentiate, at least some of their daughter cells remain as HSCs so the pool of stem cells is not depleted. This phenomenon is called asymmetric division. The other daughters of HSCs (myeloid and lymphoid progenitor cells) can follow any of the other differentiation pathways that lead to the production of one or more specific types of blood cell, but cannot renew themselves. The pool of progenitors is heterogeneous and can be divided into two groups; long-term self-renewing HSC and only transiently self-renewing HSC, also called short-terms. This is one of the main vital processes in the body. As a stem cell matures it undergoes changes in gene expression that limit the cell types that it can become and moves it closer to a specific cell type (cellular differentiation). These changes can often be tracked by monitoring the presence of proteins on the surface of the cell. Each successive change moves the cell closer to the final cell type and further limits its potential to become a different cell type. Mesenchymal stem cells (MSCs) and hematopoietic stem cells (HSCs) are indeed the primary types of stem cells found in bone marrow, but they are not the only ones. Hematopoietic Stem Cells (HSCs): These are responsible for producing all the blood cells, including red blood cells, white blood cells, and platelets Mesenchymal Stem Cells (MSCs): These can differentiate into a variety of cell types, including bone cells (osteoblasts), cartilage cells (chondrocytes), and fat cells (adipocytes) Lara HADDAD Introduction Because the human body provides an ideal environment for many microbes, they try to pass your skin barrier and enter. 1st line of defense: Skin Mucus The immune system is a body wide network of cells, tissues, and organs that has evolved to defend us against  "foreign" invasions  cancer Lara HADDAD  stem cell=Progenitor, blast, precursor Introduction The proper targets of your immune system are infectious organisms NK cells are cells of lymphoid progenitor but have phagocytic properties ex: Acute myeloid leukemia AML when wanting to donate blood to such patient first of all we have to assess: Blood group, Histocompatibility, NK kir (Natural killer (NK) cells are part of the cellular immune response. They target mainly cancer and virally infected cells. To a high extent cytotoxic activity of NK cells is regulated inter alia by signals from killer immunoglobulin-like receptors (KIR). The major histocompatibility complex (MHC) class I molecules are important ligands for KIR receptors. Binding of ligands (such as MHC I) to the KIR receptors has the important role in solid organ or hematopoietic cell transplantation importance of interactions between KIR receptors and HLA in predicting the risk of allograft rejection, protection against post-transplant CMV infection, graft-versus-host disease (GVHD) and pregnancy complications. NK kir are receptors found on the surface of NK cells, high capity of high cytotoxiic effect of Nk cells, Nk cells 3al surface tab3iton fi receptors (the receptors found on cells are called identity card of the cell, identity card are markers present on the surface of the cells, Nk cells have Kir, which are receptors on the surface of Nk cells, those receptors have the capacity to bind to specific antigens which are HLA (human leukocyte antigen: system or complex of genes on chromosome 6 in humans which encode cell-surface proteins responsible for regulation of the immune system. The HLA system is also known as the human version of the major histocompatibility complex (MHC) found in many animals.HLAs corresponding to MHC class I (A, B, and C), all of which are the HLA Class1 group, present peptides from inside the cell. For example, if the cell is infected by a virus, the HLA system brings fragments of the virus to the surface of the cell so that the cell can be destroyed by the immune system. These peptides are produced from digested proteins that are broken down in the proteasomes. In general, these particular peptides are small polymers foreign antigens presented by MHC class I attract T-lymphocytes called killer T-cells (also referred to as CD8-positive or cytotoxic T-cells) that destroy cells HLAs corresponding to MHC class II (DP, DM, DO, DQ, and DR) present antigens from outside of the cell to T-lymphocytes. These particular antigens stimulate multiplication of T-helper cells (also called CD4-positive T cells), which in turn stimulate antibody-producing B-cells to produce antibodies to that specific antigen. Self-antigens are suppressed by regulatory T cells. The proteins encoded by HLAs are those on the outer part of body cells that are (in effect) unique to that person. The immune system uses the HLAs to differentiate self cells and non-self cells. Any cell displaying that person's HLA type belongs to that person and is therefore not an invader When a foreign pathogen enters the body, specific cells called antigen-presenting cells (APCs) engulf the pathogen through a process called phagocytosis. Proteins from the pathogen are digested into small pieces (peptides) and loaded on to HLA antigens (to be specific, MHC class II). They are then displayed by the antigen-presenting cells to CD4+ helper T cells, which then produce a variety of effects and cell-to-cell interactions to eliminate the pathogen. Through a similar process, proteins (both native and foreign, such as the proteins of viruses) produced inside most cells are displayed on HLAs (to be specific, MHC class I) on the cell surface. Infected cells can be recognized and destroyed by CD8+ T cells.), HLA of tumor cells, antigens of tumor cells (ex we have 2 donors and a clinical case, we look at the blood group, we look at the histocompatibility complex, we look at the donor that has active NK cells to check compatibility between donor receptors and antigens present on the surface of tumor cells, kl ma ken 3ena aktr receptors that can bind to the antigen present on the tumor cell kl ma kenit l capacity to attack those tumor cells and kill them ) What are the proteins that are going to decide whether the stem cells are going to be of myeloid lineage or lymphoid, and what protein eza myeloid lineage bt3tine neutrophil msln msh basophil wala platelet, aw t cell msh b cell, li bt3mol control? in other words what molecule will decide the mechanism of signaling pathway to give rise to specific cell in the immune system? CYTOKINES, depending on here quantity, quality, concentration, type. Cytokine attach to receptor or markers on the cell which will trigger a cascade of signaling pathways, or a cascade of phosphorylation of proteins, cascade of activation of deactivation, ex nfs l shi cytokine binds.. hal binding induces cascade hal cascade will activate a molecule/protein after the other till reaching the nucleus, upon reaching the nucleus, one of the proteins that reach the nucleus plays the role of a transcription factor ( A transcription factor is a protein that controls the rate of transcription of genetic information from DNA to messenger RNA1. It does this by binding to a specific DNA sequence1. The activity of a gene is controlled by transcription factors, which determine whether the gene's DNA is transcribed into RNA2. RNA polymerase catalyzes the chemical reactions that synthesize RNA, using the gene's DNA as a template) and protein production occurs and then these proteins are then translocated into the surface of the cell, hence the cell starts expressing new proteins that it did not express before lets say it was myeloid progenitor now it is expressing on its surface, proteins ( of course minding the quantity and type and concentration) that are specific let's say to erythrocytes hence making it differentiate and be more specialized into erythrocyte. Pro-inflammatory cytokines trigger or heighten inflammation. They relay messages that coordinate your body’s immune response to fend off attackers, like germs. Anti-inflammatory cytokines stop or lessen inflammation. They relay messages that prevent an excessive immune response that can lead to tissue damage. 1st line of defense, physical barriers skin+ mucus (released by goblet cells which are found scattered among the epithelial lining of organs. Some re0gions where goblet cells are found include: Respiratory tract: trachea, bronchi, and bronchioles, Gastrointestinal tract: small intestine and large intestine, Membrane of the eye and eyelid: conjunctiva in the upper eyelid 2st line defense innate (non-specific ex macrophages, phagocytes), adaptive (specific ex antibodies, cytotoxic T cells, Helper T cells) 2 molecules that are antigen presenting cells are dendritic cells and macrophages!!! T cells have receptors called TCR (T cell receptors), B cells have BCR (B cell receptors), Dendritic cells are cells that are a bridge between innate and adaptive immune system called bridge cells or antigen presenting cells, they recognize foreign particles and transport them and make them recognized by the immune system, B cell and T cell can recognized some antigens/ proteins present on activated dendritic cells hence they in their turn into activated T cells and B cells once activated helper T cells release cytokines that activate cytotoxic T cells and B cells (to be differentiated into plasma cells to produce antibodies) PAMPs are patterns of microorganisms, identity/ profile of microbes. immune cells mainly innate recognize these PAMPs as foreign and then the cascade... protein, reach nucleus, g there will be activation of proinflammatory genes ex of proinflammatory genes NFK B) , these proinflammatory genes will produce proinflammatory proteins which will be released into the blood Lara HADDAD Introduction Lara HADDAD Introduction The immune system main functions are: Immunological recognition Immune effectors functions Immune regulation Immunological memory Lara HADDAD Introduction An immune response can be divided into 2 interrelated activities:  Recognition  Response Immune recognition is remarkable for its specificity. Lara HADDAD Introduction At the heart of the immune response is the ability to distinguish between "self" and "non-self." Every cell in the body carries the same set of distinctive surface proteins that distinguish us as "self." Normally the immune cells do not attack our own body tissues, which all carry the same pattern of self-markers; rather, your immune system coexists peaceably with our other body cells in a state known as self-tolerance. Lara HADDAD Introduction Lara HADDAD Introduction However, once a foreign organism is recognized, the immune system enlists the participation of a variety of cells and molecules to mount an appropriate response: the effector response to eliminate or neutralize the organism. Later exposure to the same foreign organism induces a memory response characterized by a heightened immune reactivity. This diagram is an illustration of the response of an acquired / adaptive immunity whereas the response of an innate immunity will remain like the "primary immune response" part of this diagram since innate immunity has no memory Lara HADDAD Innate/acquired immunity Although the type of soldiers the immune system deploys, and the protective strategy it uses, depend on the type of invader, the immune system defense generally consists of two collaborative systems:  the innate immune system  the adaptive immune system Lara HADDAD Innate/acquired immunity Humoral immunity is the aspect of immunity that is mediated by macromolecules – including secreted antibodies, complement proteins, and certain antimicrobial peptides – located in extracellular fluids. Humoral immunity is named so because it involves substances found in the humors, or body fluids. It contrasts with cell-mediated immunity. Humoral immunity is also referred to as antibody-mediated immunity. Humoral immunity refers to antibody production and the coinciding processes that accompany it, including: Th2 activation and cytokine production, germinal center formation and isotype switching, and affinity maturation and memory cell generation. It also refers to the effector functions of antibodies, which include pathogen and toxin neutralization, classical complement activation, and opsonin promotion of phagocytosis and pathogen elimination Lara HADDAD Innate immunity The innate immunity system is what we are born with and it is nonspecific. It is genetically based and we pass it on to our offspring. It involves 4 types of defensive barriers:  Anatomic  Physiologic  Endocytic and phagocytic  Inflammatory Lara HADDAD Acquired immunity Acquired (adaptive or specific) immunity is not present at birth. It is learned. Lymphocytes mainly meaning B cells, T cells, NK cells Both B cells and T cells develop from bone marrow-derived progenitors; B cells mature in the bone marrow, T cell development, maturation and export occur in the thymus Acquired or specific immunity reflects the presence of a functional immune system that is capable of specifically recognizing and selectively eliminating foreign microorganisms and molecules. Lara HADDAD Acquired immunity Lara HADDAD Acquired immunity Lymphocytes are the type of white blood cell responsible for acquired immunity. Lymphocytes come in two major types:  B cells  T cells The peripheral blood contains 20–50% of circulating lymphocytes; the rest move in the lymph system. Roughly 80% of them are T cells, 15% B cells and remainder are null or undifferentiated cells. Lara HADDAD Acquired immunity B cells are produced in the stem cells of the bone marrow; they produce antibody and oversee humoral immunity or antibody mediated immunity (AMI). Lara HADDAD Acquired immunity T cells are non antibody- producing lymphocytes which are also produced in the bone marrow but sensitized in the thymus and constitute the basis of cell-mediated immunity (CMI). Lara HADDAD Lara HADDAD Innate and Acquired immunity Immunity can be either natural or artificial, innate or acquired, and either active or passive. Lara HADDAD Innate and Acquired immunity  Active natural (contact with infection): develops slowly, is long term, and antigen specific  Active artificial (immunization): develops slowly, lasts for several years, and is specific to the antigen for which the immunization was given Lara HADDAD Innate and Acquired immunity  Passive natural (transplacental = mother to child): develops immediately, is temporary, and affects all antigens to which the mother has immunity  Passive artificial (injection of gamma globulin): develops immediately, is temporary, and affects all antigens to which the donor has immunity Lara HADDAD Innate and Acquired immunity Lara HADDAD  The scope of immunity Immunology at a Glance, 9e. By J.H.L. Playfair and B.M. Chain. Lara HADDAD Hematopoiesis In humans, hematopoiesis is the formation of red and white blood cells from pluripotent hematopoietic stem cells. Asymmetic division y3ne l stem cell bta3tina copy 3anna w we7de differntiated, law we go through symetric division ma ken fadal 3ena stem cells to replace the damaged ones Lara HADDAD Lara HADDAD Hematopoiesis An HSC can enter one of two pathways  the lymphoid pathway  the myeloid pathway If it forms the lymphoid progenitor, it can become either:  a B progenitor that forms a mature B cell  a T progenitor that forms a thymocyte which leaves the bone marrow and enters the thymus, where it differentiates to form a mature T cell (helper or cytotoxic). Lara HADDAD Hematopoiesis Hematopoiesis is a very carefully regulated process. It is regulated by complex mechanisms that affect all of the individual cell types. These regulatory mechanisms ensure steady-state levels of the various blood cell; yet they have enough flexibility to meet excessive demands of blood cells in case of hemorrhage or infections. Lara HADDAD Hematopoiesis Regulation is accomplished in various ways, including:  control of the levels and types of cytokines produced by bone marrow stromal cells  production of cytokines with hematopoietic activity by other cell types, such as activated T cells and macrophages  regulation of the expression of receptors for hematopoietically- active cytokines in stem cells and progenitor cells  removal of some cells by the controlled induction of cell death (apoptosis) Lara HADDAD Hematopoiesis Lara HADDAD Immune-system organs The immune system consists of many structurally and functionally diverse organs and tissues disseminated throughout the body. Lara HADDAD Immune-system organs The organs and tissues of the system can be classified into two main groups: 1. primary lymphoid organs  Bone marrow and the thymus  Regulate the development of immune cells from immature precursors Lara HADDAD Immune-system organs 2. secondary lymphoid organs and tissues  Spleen, lymph nodes, and specialized sites in the gut and other mucosal tissues  Coordinate the encounter of antigen with antigen-specific lymphocytes and their development into effector and memory cells Lara HADDAD Introduction Lara HADDAD Immune-system cells The vessels of the blood and lymphatic systems connect lymphoid organs and tissues and unite them into a functional whole. Leukocytes, or white blood cells (WBC), are found within the  Blood  Lymph  Lymphoid tissues and organs Lara HADDAD Immune-system cells The vertebrate immune system contains many types of leukocytes, but only the lymphocytes have the attributes of:  Receptor diversity  Antigen specificity hallmarks of an immune response  Memory  Self/nonself recognition Lara HADDAD Immune-system cells All other cells play accessory roles, serving:  to activate lymphocytes  to increase the effectiveness of antigen clearance by phagocytosis  to secrete various effector molecules Lara HADDAD Immune-system cells Lymphocytes are the central cells of the immune system. The other types of WBCs play ancillary roles by:  Engulfing and destroying microorganisms  Presenting antigens  Secreting cytokines Lara HADDAD 1-Lymphoid cells Lymphocytes represent 20-40% of circulating WBC in blood and 99% of the cells in the lymph Lymphocytes circulate in the blood and lymph but can also extravasate and enter the tissues Lymphocytes are divided on the basis of function and cell membrane components into:  T lymphocytes  B lymphocytes small, motile and non phagocytic  Null cells Lara HADDAD 1-Lymphoid cells Naïve cells or small lymphocytes: B and T cells that did not yet interact with and antigen and are resting at G0 Lymphoblasts: B and T cells after antigen interaction, progression in the cell cycle and differentiation into  B cells effectors: plasma cells  T cells effectors: TH, CTL and memory cells Lara HADDAD 1-Lymphoid cells Lara HADDAD 1-Lymphoid cells-B cells Mature in the bone marrow Each B cell express a unique BCR, a membrane-bound immunoglobulin (antibody) molecule that binds to antigen Activated B cells differentiate into effector cells known as plasma cells that secrete antibodies Lara HADDAD 1-Lymphoid cells-T cells Mature in the thymus Each express a unique TCR that only binds processed antigens in the context of MHC molecules  If it is a TH lymphocyte, the cell also expresses CD4, and recognize antigen associated with class II MHC molecules  TH0, TH1, TH2, TH9, TH17 Lara HADDAD 1-Lymphoid cells  If it is a Tc lymphocyte, the cell also expresses CD8, and recognize antigen associated with class I MHC molecules.  Suppressor T cells (also called Regulatory T cells):  limit responses of other cells (B & T cells)  make immune response self-limiting  prevents excessive immune response which might be detrimental to body  may also prevent immune system from attacking a person's own cells & tissues Lara HADDAD 1-Lymphoid cells Lara HADDAD 1-Lymphoid cells Lara HADDAD 1-Lymphoid cells-NK cells  natural killer cells:  These cells are large, granular, and represent 5-10% of the peripheral blood lymphocytes  NK cells kill tumor cells or virally-infected cells by direct membrane contact or through antibody-dependent cell- mediated cytotoxicity (ADCC)  Do not express antigen-specific receptors and are considered part of the innate immune system  Contain cytotoxic granules Lara HADDAD 1-Lymphoid cells-NK cells Lara HADDAD Antigen Presenting Cells (APCs) Considered cellular bridges between the innate and adaptive immune systems They make contact with a pathogen at the site of infection and communicate this encounter to T lymphocytes in the lymph node Digest pathogenic proteins into peptides, then present these peptide antigens on their membrane surfaces Lara HADDAD Antigen Presenting Cells (APCs) Lara HADDAD 2- APC- Mononuclear cells The mononuclear phagocytic system consists of:  Monocytes in the blood  Macrophages in the tissues Lara HADDAD 2- APC- Mononuclear cells-Monocytes 5% to 10% of white blood cells Monocytes circulate in the blood and lymph for about 8h before migrating to the tissues and differentiate into specific tissue macrophages Changes in the monocytes which occur during this transition:  Cells enlarge [5-10x]  Intracellular organelles increase in number and complexity  Cells acquire increased phagocytic ability  Increased secretion of many soluble factors and lytic enzymes Lara HADDAD 2- APC- Mononuclear cells- Macrophages Macrophages play the following important roles: 1. phagocytosis 2. antimicrobial activity 3. secretion of soluble factors 4. antigen presentation 5. regulating tissue repair and regeneration 6. participate in the innate immune response Lara HADDAD 2- APC- Mononuclear cells- Macrophages Macrophages are activated by a variety of stimuli in the course of an immune response. a. One of the earliest activating signals comes from chemokines b. Phagocyotosis itself is an important activating stimulus c. Macrophages are further activated by cytokines secreted by T helper cells [IFN-gamma] d. and by mediators of the inflammatory response e. and by various microbial products (such as LPS) Lara HADDAD APC- Dendritic cells Dentritic cells  These cells function as "professional" antigen presenting cells  Considered the most efficient activator of naïve T cells  They process pathogenic antigens → then migrate to lymph nodes → present the antigen to naïve T cells → initiate the adaptive immune response Lara HADDAD APC- Dendritic cells Antigen Presenting Cells (APCs) 3-Granulocytic cells Granulocytes are classified as:  Neutrophils (multilobed nucleus) 62% Phagocytic  Eosinophils (bilobed nucleus) 2.3%  Basophils (lobed nucleus) 0.4% Lara HADDAD 3-Granulocytic cells Front lines of attack during an immune response Considered part of the innate immune system Lara HADDAD 3-Granulocytic cells Neutrophils  The neutrophil is a phagocytic cell, particularly important in the phagocytosis of bacteria  However, these cells DO NOT function as APCs.  The granules of the neutrophils fuse with phagosome to destroy internalized bacteria  Primary granules contain bactericidal enzymes such as lysozyme and myeloperoxidase; neutral proteases and acid hydrolases  Secondary granules are smaller and contain lysozyme, collagenase and lactoferrin Lara HADDAD 3-Granulocytic cells Used medically as an indication of infection Lara HADDAD 3-Granulocytic cells Eosinophils  Phagocytic but DO NOT act as APCs.  The major role of the eosinophil is believed to be against parasites  Eosinophils kill by binding to parasite - specific IgE via cell surface Lara HADDAD 3-Granulocytic cells Basophils  They play a major role in the allergic response when they release their granules (containing histamine, serotonin, heparin, prostaglandin, etc into the bloodstream following exposure to specific allergens).  Non-phagocytic  Important against parasites, particularly helminths (worms) Lara HADDAD 4-Mast cells Mast cells  Mast cells are released from the bone marrow as undifferentiated precursor cells and do not differentiate until they enter the tissues (skin, connective tissue, mucosal epithelium, etc.)  Morphology and function similar to circulating basophils - but clearly derived from a distinct cell lineage.  Mast cells also play a very important role in the allergic response. Lara HADDAD 4-Mast cells  More recently, experimental evidence has shown that mast cells express class II MHC and are capable of presenting peptides to TH lymphocytes.  They also produce a variety of cytokines (including the very potent pro-inflammatory cytokine TNF-α.  In fact, TNF is produced and stored within the cytoplasm of the mast cell, and it can be released quickly following mast cell activation. Lara HADDAD 4-Mast cells Lara HADDAD Immunological recognition The immune system main functions are:  Immunological recognition - Immune cells recognize foreign molecules and pathogens through their PAMPs or antigens a. PAMPs - Pathogen-Associated Molecular Patterns - Recognized by cells of innate immunity - Pattern recognition receptors (PRRs) Lara HADDAD Immunological recognition b. Antigens - Any substance that stimulates antibody generation - Any substance that can be recognized and responded to by the adaptive immune system - Any molecules that interact with the immunoglobulin receptor of B cells (or with the T-cell receptor when complexed with MHC). Lara HADDAD Immune effectors functions  Immune effectors functions Lara HADDAD Immune regulation  Immune regulation - The ability of the immune system to self-regulate - When the immune system malfunctions, it can unleash a torrent of disorders and diseases: 1. Hypersensitivity reaction 2. Autoimmune disease 3. Immune deficiency 4. Graft rejection 5. GVHD Lara HADDAD Immunological memory  Immunological memory - The ability of the immune system to generate a long-lasting immunity to pathogens following any subsequent exposure. a. Faster with memory b. Generation of diversity and clonal expansion Lara HADDAD Terminology  Cytokines - Leuckocyte development, activation, and function - E.g interleukins  Chemokines - Chemotaxis (Migration) - Some cytokines can also induce chemotaxis  Cell signalling - Intracellular transduction pathways induced by cytokines, chemokines, and cell-bound receptors Lara HADDAD