Immunology PDF

Define Immunology and recognise the terminology associated with it -The immune system refers to a collection of cells, chemicals and processes that function to protect the skin, respiratory passages, intestinal tract and other areas from foreign antigens, such as microbes (organism such as bacteria,...

Define Immunology and recognise the terminology associated with it -The immune system refers to a collection of cells, chemicals and processes that function to protect the skin, respiratory passages, intestinal tract and other areas from foreign antigens, such as microbes (organism such as bacteria, fungi, and parasites), viruses, cancer cells, and toxins. Terminology: Two Lines of defense : innate immunity and adaptive immunity Describe the natural defense systems of the body Blood Cells -Granulocytes→ type of leukocyte that contains granules in their cytoplasm containing enzymems. -i.e Neutrophils, basophils, eosinophils are types of granulocytes Neutrophils-> first line of defense Neutrophil & macrophage circulate around the blood and reside in the tissue. Cell of adaptive immune system (aka immune effector cells) - i.e NK T lymphocytes and B lymphocytes. Activated T lymphocyte destroy pathogen via cell-mediated response Activated B secrete antibodies Both can destroy cancer Non-effector cells → antigen-presenting cells (APCs) i.e dendritic cells, regulatory T cells, tumor-associated macrophages and myeloid-derived suppressor cells. -Cannot cause tumor death on their own. Identify the components and functions of the non-specific (innate) and adaptive (acquired) immune systems -Innate Innate immunity to pathogens relies on pattern recognition receptors (PRRs) which allow a limited range of immune cells to detect and respond rapidly to a wide range of pathogens that share common structures, known as pathogen associated molecular patterns (PAMPs). Examples of these include bacterial cell wall components such as lipopolysaccharides (LPS) and double-stranded ribonucleic acid (RNA) produced during viral infection. An important function of innate immunity is the rapid recruitment of immune cells to sites of infection and infammation through the production of cytokines and chemokines (small proteins involved in cell– cell communication and recruitment). Cytokines: mobilize defense mechanism and same time activate local cellular response; release tumor necrosis factor (TNF), interleukin 1 IL-1, interleukin 6 IL-6; critical for recruiting and local inflammation to clear the pathogen but also can contribute to develop fever. -Acquired The development of adaptive immunity is aided by the actions of the innate immune system, and is critical when innate immunity is ineffective in eliminating infectious agents. The primary functions of the adaptive immune response are: the recognition of specific “nonself” antigens, distinguishing them from “self” antigens; the generation of pathogen-specific immunological effector pathways that eliminate specific pathogens or pathogen-infected cells; and the development of an immunologic memory that can quickly eliminate a specific pathogen should subsequent infections occur. Differentiate between non-specific (innate) and adaptive (acquired) immunity -Innate First line of defense to an intruding pathogen Antigen-independent (non-specific) Used by host immediately or within hours of encountering an antigen No immunologic memory thus not able to recognise the same pathogen if it attack in future -Acquired Antigen-dependent and antigen specific lag time between exposure to antigen and maximal response Recognise and list the cells of the nonspecific immune system and the adaptive immune system -Innate Phagocytes (macrophages and neutrophil): similar functions i.e to engulf and eliminate microbes through multiple bactericidal pathways Neutrophils contains granules and enzymes which assist in eliminating microbes; and are short-lived cells, macrophages- long lived cells and involve in antigen presentation to T cells. Dendritic cells : also phagocyte and function as APCS. Initiate the acquired immunity response and act as an important messenger between innate and acquired immunity. Mast cells and Basophils: share important features with each other , both initiate of acute inflammatory response such as allergy and asthma. Mast cell; sentinel cells , are early producers of cytokines in response to infection or injury, resides in the connective tissue surrounding blood vessels and mucosal surfaces:. Basophils reside in circulation. Eosinophils: granulocytes that possess phagocytic properties, plays important role in destruction of parasites that are often too large to be phagocytosed. Also associated with allergy and asthma. Natural Killer (NK cells): Major role in the destruction of tumor and destruction of cells infected by virus. how does it destruct? - by releasing perforins and granzymes (proteins that cause lysis of target cells) from NK cell granules which induce apoptosis (programmed cell death). -source of another cytokine, interfernon-gamma (IFN-y) which helps to mobilize APCs and promote the development of effective anti-viral immunity. Innate lymphoid cell: plays regulatory role, depends on the type, they selectively produce cytokines ie. IL-4, IFN-y, IL-17 to help direct appropritate immune reponse to specific pathogen and contribute to immune regulation in that tissue. -Acquired Antigen-specific T cells : activated to proliferate through the action of APCs :T-cell derive from hematopoietic stem cells in bone marrow following migration and mature in thymus. Express a series of unique antigen-binding receptors on their membrane known as T-cell receptor (TCR). Expresses a single type of TCR and has the capacity to rapidly proliferate and differentiate if it receives the appropriate signals. T cells require the action of APCs (usually dendritic cells, but also macrophages, B cells, fibroblasts and epithelial cells) to recognize a specific antigen. The surfaces of APCs express a group of proteins known as the major histocompatibility complex (MHC). Class I MHC molecules present endogenous (intracellular) peptides, while class II molecules on APCs present exogenous (extracellular) peptides to T cells. B Cells: differentiate into plasma cells to produce antibodies. -B cells arise from hematopoietic stem cells in the bone marrow and, following maturation, leave the marrow expressing a unique antigen-binding receptor on their membrane. Unlike T cells, B cells can recognize antigens directly, without the need for APCs, through unique antibodies expressed on their cell surface. The principal function of B cells is the production of antibodies against foreign antigens which requires their further differentiation. -B cells undergo proliferation and diferentiate into antibody-secreting plasma cells or memory B cells -Memory B cells are “long-lived” survivors of past infection and continue to express antigen-binding receptors -Plasma cells, on the other hand, are relatively short-lived cells that often undergo apoptosis when the inciting agent that induced the immune response is eliminated. However, these cells produce large amounts of antibody that enter the circulation and tissues providing efective protection against pathogens. -Given their function in antibody production, B cells play a major role in the humoral or antibody-mediated immune response (as opposed to the cell-mediated immune response, which is governed primarily by T cells) Glossary Pattern recognition receptors (PRRs) Pathogen associated molecular patterns (PAMPs) Lipopolysaccharides (LPS) double-stranded ribonucleic acid (RNA) Cytokines Chemokines Tumor necrosis factor (TNF) Interleukin 1 (IL-1) Interleukin 6 (IL-6) Opsonize (coat) Phagocytosis: process by which immune cells engulf microbes and remove cell debris, and also kills some pathogens and infected cells directly antigen presenting cells (APCs) Salient: Important Perforins granzymes T-cell receptors major histocompatibility complex (MHC) Mucosal associated lymphoid tissue (MALTS) Guts associated lymphoid tissue (GALTs) Organs and tissues of the immune system in the immunology -Skin: First line of defense; physical barrier -Mucous membranes - First line of defense ;physical barrier -Blood and the organs of the lymphatic system Antibacterial substances→ i.e certain enzyme found in saliva, airway and tear fluid can destroy cell walls of bacteria. Mucus→ i.e in the bronchi trap many germs so when we breath they can be move out of the airways by a hair-like-structure called cilia. Stomach acid→ stops most of the germs that enter the body in the food we eat. Harmless bacteria→ on our skin and many of the mucous membranes in our body are also a part of the immune system. Lymphoid Organs Primary lymphoid organs: organs include bone marrow and the thymus. They make special immune system cells called lymphocytes Secondary lymphoid organs: organs include lymph nodes, the spleen, the tonsils, certain tissues in various mucous membrane layers in the body i.e the bowel. Bone Marrow -sponge-like tissue found inside the bones. -Most-immune cells are made and multiply -Move through bloodstream -At birth, bone contains RBC -Over course of life, more and more RBC turns into fatty tissue -In adults, only few bones contains RBC, including ribs, breastbone, pelvis Thyums -located behind the breastbone, above the heart -reach full maturity only on children and slowly transform to fatty tissue -Special cell called Thymus cell Lymphocytes T cells mature in thymus -coordinate the process of innate and adaptive immune system Lymph Nodes -Small bean-shaped clumps of tissue found along the lymphatic vessels -Act as filters -Various immune system cell trap germs in the lymh nodes and trigger the production of special antibodies in the blood -If swollen or painful lymph nodes then immune system is active Spleen -found in upper left abdomen, beneath the diaphragm responsible for : =stores various immune system cells =when needed, these cells travel to other organs in the bloodstream =scavenger cells (phagocytes) act as filter for germs that get into the bloodstream =break down RBC =store and break down platelets (Thrombocytes), which are responsible for clotting for blood. -very soft -can tear easily Tonsils -Part of immune system as they are located in the throat and root of the mouth -Contain lots of WBC -Palatine tonsils, adenoids and lingual tonsil (together they form a ring of tonsil tissue, known as walderyer’s ring) Mucous Membrane -Most of the body’s cells make antibodies are found in the wall of the intestine especially on small intestine and in the appendix. -these cell detect foreign substances and then mark and destroy them. -store information about the substances so they can react more quickly the next time -the large intestine contain harmless bacteria called gut flora -Support other immune systems in other parts of the body i.e respiratory and urinary tracts and the lining of the vagina. -The immune system consists of many parts that work together to defend the body against invaders. The primary parts of the immune system include the bone marrow and thymus. The bone marrow is extremely important to the immune system because all the body’s blood cells (including T and B lymphocytes) originate in the bone marrow. B lymphocytes remain in the marrow to mature, while T lymphocytes travel to the thymus. Thymus -The thymus is a bi-lobed gland located above the heart, behind the sternum and between the lungs. The thymus is only active through puberty, then it slowly shrinks and is replaced by fat and connective tissue. -Responsible for producing the hormone thymosin, which in turn aids in the production of T cells. While in the thymus, T cells multiply, acquire different antigen receptors, and differentiate into helper T cells and cytotoxic T cells. -Various proteins (e.g., CD4, CD8) are expressed on the T cell surface. The thymus will have produced all the T cells an individual needs by puberty. -After T & B lymphocytes mature in thymus and bone marrow → they travel to lymph nodes and spleen, and remain there until the immune system is activated. -lymph nodes located throughout the body -Spleen is located upper left area of abdomen, behind the stomach and under the diaphragm. -function of spleen? : to filter the blood out, healthy RBC pass through spleen but damaged one broken down by macrophages in the spleen. -Spleen- storage for platelets and WBC , aids in the immune system by identifying microorganism that may cause infection. -MALTs-> where mucosa is present i.e intestine, nose, eyes, skin and mouth -GALTs-> where mucosa and submucosa of the gastrointestinal tract, tonsils, appendix and Peyer’s patches in the small intestine. Describe the barriers of the innate immune system. Give the mechanism for each example. Which barriers are associated with the oral cavity? -Innate immunity can be viewed as comprising four types of defensive barriers: anatomic (skin and mucous membrane), physiologic (temperature, low pH and chemical mediators), endocytic and phagocytic, and infammatory. Cells and processes that are critical for effective innate immunity to pathogens that evade the anatomic barriers have been widely studied. Innate immunity to pathogens relies on pattern recognition receptors (PRRs) which allow a limited range of immune cells to detect and respond rapidly to a wide range of pathogens that share common structures, known as pathogen associated molecular patterns (PAMPs). Examples of these include bacterial cell wall components such as lipopolysaccharides (LPS) and double-stranded ribonucleic acid (RNA) produced during viral infection. Barrier Mechanism: Anatomic (Skin) Mechanical barrier retards entry of microbes Acidic environment (pH 3–5) retards growth of microbes Anatomic (Mucous membrane) Normal fora compete with microbes for attachment sites Mucous entraps foreign microbes Cilia propel microbes out of body Physiologic Physiologic (Temperature) Body temperature/fever response inhibits growth of some pathogens Physiologic (low PH) Acidic pH of stomach kills most undigested microbes Physiologic (Chemical mediators) Lysozyme cleaves bacterial cell wall Interferon induces antiviral defenses in uninfected cells Complement lyses microbes or facilitates phagocytosis Phagocytic/endocytic barriers Various cells internalize (endocytosis) and break down foreign macromolecules Specialized cells (blood monocytes, neutrophils, tissue macrophages) internalize (phagocytose), kill and digest whole organisms Infammatory barriers Tissue damage and infection induce leakage of vascular fuid containing serum protein with antibacterial activity, leading to infux of phagocytic cells into the afected area