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

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)

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 bacteriaInterferons biologic response modifier, a nonspecific viricidal protein that is naturally produced by

the body and is capable of activating other components of the immune systemd) 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 - 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.

a)Recognition Stage b)Proliferation Stage c)Response Stage Effector Stage

4) Humoral Immune Response a)Antigen Recognitionb)Role of Antibodies c)Antigen – Antibody Bonding

5) Cellular Immune Responsea)Role of T – lymphocytes b)Roles of Null Lymphocytes and Natural Killers

6) Complement System a)Classic Pathway of Complement Activation b)Alternative and Lectin Pathways

7) Role of Interferons