Assessment Of Immune Function

ASSESSMENT OF IMMUNE FUNCTION (PP. 1783 – 1810) Immunity – refers to the body’s specific protective response to an invading foreign agent or organism Factors that affect immune function: CNS integrity, emotional status, medications, stress and illness, trauma, surgery Immune memory – a property of the immune system that provides protection against microbial agents despite the timing of re-exposure to the agent Tolerance – the process by which the immune system is programmed to eliminate foreign substances such as microbes, toxins, and cellular mutations but maintains the ability to accept self – antigens Surveillance – immune system is in a perpetual state of vigilance, screening and rejecting any invader that is recognized as foreign to the host Immunopathology – refers to the study of diseases that result from dysfunction within the immune system ANATOMIC AND PHYSIOLOGIC OVERVIEW Anatomy of the Immune System - composed of integrated collection of various cell types - molecules  responsible for interactions, modulations regulation of the system ☻molecules and cells participate in interactions with immunogenic isotopes present on foreign materials and initiate a series of actions in a host including inflammatory response, lysis of microbial agents and disposal of foreign toxins 1) Bone Marrow - produce WBCs - WBCs generated from stem cells (undifferentiated cells) - Stem Cells  B- lymphocytes (B-cells) – mature in bone marrow and then enter circulation  T – lymphocytes (T-cells) – move from bone marrow to thymus where they mature to several kinds of cells with different fxns 2) Lymphoid Tissue - spleen  composed of red and white pulp, acts somewhat like a filter, RED pulp (site where old RBCs are destroyed); WHITE pulp (contains concentrations of lymphocytes) - lymph nodes  distributed al throughout the body  connected by lymph channels and capillaries which remove foreign material from the lymph system before it enters the bloodstream  serve as centers for immune cell proliferation - remaining lymphoid tissue contain immune cells that defend body’s mucosal surfaces against microorganisms

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Immune Function 1) Natural (innate) Immunity provides rapid nonspecific immunity and is present at birth has a broad spectrum of defense a@1 111 Ï¿ð8esistance to infection provides a nonspecific response to any foreign invader’s composition basis of the defense mechanism: the ability to distinguish between friend and foe coordinates the initial response to pathogens through the production of cytokines and other effector molecules, which either activates cells for control of the pathogen (by elimination) or promote the development of the acquired immune response cells involved: macrophages, dendritic cells and natural killer (NK) cells NK cells - have the ability to recognize and respond to a wide variety of pathogens long before the development of antigen – specific acquired immunity mechanisms: immediate (occurring within 4 hours) and delayed (occurring within 4-96hours after exposure)

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a) White Blood Cell Action cellular response is key to effective initiation of immune response participate in both natural and acquired immune responses ◘ Granular leukocytes (Granulocytes) – fight invasion by foreign bodies or toxins by releasing cells mediators, such as histamine, prostaglandins, bradykinin, and engulfing foreign bodies or toxins • Neutrophils / Polymorphonuclear Leukocytes - first cells to arrive at the site where inflammation occurs - 45% - 73% - increased in acute infections, trauma or surgery, leukemia, malignant disease, necrosis - decreased with viral infections, bone marrow suppression, primary bone marrow dse • Eosinophils – 0% - 4% - increased in allergy, parasitic dse, collagen dse, subacute infections, - decreases with stress, use of some meds (ACTH, epinephrine, thyroxine) • Basophils – 0% - 1% - increased with acute leukemia and following surgery or trauma, - decreased with allergic rxns, stress, allergy, parasitic dse, use of corticosteroids ◘ Nongranular leukocytes • Monocytes – fxn as phagocytic cells, engulfing, ingesting, and destroying greater numbers and quantities of foreign bodies or toxins than granulocytes - 2% – 8 % - ↑: viral infections, parasitic dse, collagen and hemolytic disorders - ↓: use of corticosteroids, RA, HIV infection • Lymphocytes - consisting of B- cells and T- cells plays major roles in humoral and cell – mediated immune responses - 20% - 40% - ↑: infectious mononucleosis, viral and some bacterial infections - ↓: aplastic anemia, SLE, immunodeficiency including AIDS b) Inflammatory Response - major function of the natural immune system that is elicited in response to tissue injury or invading organisms - chemical mediators assist this response by minimizing blood loss, walling off invading organism, activating phagocytes, promoting formation of fibrous scar tissue and regeneration of tissue - facilitated by physical and chemical barriers that are part of the human organism c) Physical and Chemical Barriers - Physical : intact skin, mucous membranes, cilia of the respiratory tract (cough and sneezing responses) - Chemical : mucus acidic gastric secretions, enzymes in tears and saliva, substances in sebaceous and sweat secretions : act in a nonspecific way to destroy invading fungi and bacteria Interferons biologic response modifier, a nonspecific viricidal protein that is naturally produced by the body and is capable of activating other components of the immune system d) Immune Regulation - involves balance and counterbalance - Dysfunction  immune components are inactivated, remain active long after their effects are beneficial - Immunodeficiencies  char. By inactivation or impairment of immune functions and disorders with an inflammatory compenent  persistent inflammatory responses - Autoimmune  immune system’s recognition of one’s own tissues as foreign rather than as self - microbial infections induce inflammatory response mediated by T-cells and cytokines (may cause tissue damage when excess) - regulatory mechanisms – achieved by cytokines and transformation of growth factor  inhibits macrophage activation -Immunoregulation – holds promise of preventing graft rejection and aiding body in eliminating cancerous and infected cells

2) Acquired (Adaptive) Immunity

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immunologic responses acquired during life but not present at birth usually develops as a result of prior exposure to an antigen through immunization or by contracting a dse, both of which generate a protective immune response - relies on the recognition of specific antigens - broadly divided into two mechanisms: Cell – mediated involving T – cell activation Effector  involving B- cell maturation and production of antibodies - Types: Active  immunologic defenses are developed by the person’s own body; lasts many years or lifetime Passive  temporary immunity transmitted from a source outside the body that has developed immunity through previous disease or immunization (e.g. immune globulin or antiserum from plasma of people who acquired the dse, mother to fetus, breastfeeding) 3) Response to Invasion ◘Phagocytic immune response  involves the WBCs (granulocytes and macrophages), which ingest foreign particles - remove body’s own dying or dead cells - Apoptosis: programmed cell death; the body’s way of destroying worn –out cells such as blood or skin cells or cells that have to be renewed : involves digestion of DNA by endonucleases which result in targeting cells for phagocytosis - eosinophils  kill parasites by releasing specific chemical mediators into extracellular fluids.

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a) Recognition Stage b)Proliferation Stage c) Response Stage Effector Stage Humoral Immune Response a) Antigen Recognition b)Role of Antibodies c) Antigen – Antibody Bonding Cellular Immune Response a) Role of T – lymphocytes b)Roles of Null Lymphocytes and Natural Killers Complement System a) Classic Pathway of Complement Activation b)Alternative and Lectin Pathways Role of Interferons