Immune Function

The Immune System • Immunity: the body’s specific protective response to

invading foreign agent or organism • Immunopathology: the study of diseases that result from dysfunction of the immune system Disorder • Immune System Disorders: Descriptions Autoimmunity

N° protective immune response paradoxically turns against or attacks the body, leading to tissue damage

Hypersensitivity

Body produces inappropriate or exaggerated responses to specific antigens

Gammopathies

Immunoglobulins are overproduces

Immune deficiencies Primary

Deficiency results from improper development of immune congenital or inherited

Secondary

Deficiency results from some interference with an already developed

Central and Peripheral Lymphoid Organs

Immune Function • Natural immunity: nonspecific response to any foreign invader White blood cell action: release cell mediators such as histamine, bradykinin, and prostaglandins, and engulf (phagocytize) foreign substances Inflammatory response Physical barriers, such as intact skin, chemical barriers, and acidic gastric secretions or enzymes in tears and saliva

• Acquired immunity: specific against a foreign antigen Result of prior exposure to an antigen Active or passive

Development of Cells of the Immune System

Lymphocytes • B lymphocytes mature in the bone marrow; T lymphocytes mature in the thymus where they also differentiate into cells with various functions

Stages of Immune Response

Response to Invasion: Defenses •

Phagocytic immune response - WBC (granulocytes & macrophages) to ingest foreign particles

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Humoral or antibody response - starts with the B-lymphocytes, then transform to plasma cells (antibodies)

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Cellular immune response - involves the T-lymphocytes, turns into cytotoxic (killer T-cells ) and attacks the pathogen

Differences in Cellular and Humoral Immune Responses: Humoral Responses (B-cells) Cellular Responses (T-cells) ▪ Bacterial phagocytosis and lysis

▪ Transplant rejection

▪ Anaphylaxis

▪ Delayed hypersensitivity (tuberculin reaction)

▪ Allergic hay fever and asthma ▪ Graft-versus-host disease ▪ Immune complex disease

▪ Tumor surveillance or destruction

▪ Bacterial and some viral infections

▪ Intracellular infections ▪ Viral, fungal, and parasitic

Stages of Immune Response

Antibody Molecule

Role of Antibodies • Agglutination of antigens • Opsonization • Promote release of vasoactive substances; activation of complement system and phagocytosis • Act in concert with other components of the immune system • Types of immunoglobulins: IgA, IgD, IgE,IgG, and IgM

Major Characteristics of the Immunoglobulins: • IgG (75% of total Immunoglobulin) ▪ Appears in serum and tissues ▪ Assumes a major role in bloodborne and tissue infections ▪ Activates the complement system ▪ Enhances phagocytosis ▪ Crosses the placenta • IgA (15% of total Immunoglobulin) ▪ Appears in body fluids ▪ Protects against respiratory, GIT, and GUT infections ▪ Prevents absorption of antigen from food ▪Passes to neonate in breast milk for protection

IgM (10% of total Immunoglobulins) ▪ Appears mostly in intravascular system ▪ Appears as the 1st immunoglobulin produced in response to bacterial and viral infections ▪ Activates the complement system

IgD (0.2% of total Immunoglobulins) ▪ Appears in small amount in serum ▪ Possibly influences B-lymphocyte differentiation, but role is unclear

IgE (0.004% of total Immunoglobulins) ▪ Appears in serum ▪ Takes part in allergic and some hypersensitivity reactions ▪ Combats parasitic infections

Antigen–Antibody Binding

Cellular Immune Response • B lymphocytes: humoral immunity – Produce antibodies or immunoglobulins

• T lymphocytes: cellular immunity – Attack invaders directly, secrete cytokines, and stimulate immune system responses – Helper T cells – Cytotoxic T cells – Memory cells – Suppressor T cells (suppress immune response)

Non-T and Non-B Lymphocytes Involved in Immune Response • Null cells – Destroy antigen coated with antibody

• Natural killer cells – Defend against microorganisms and some malignant cells

Complement-Mediated Immune Responses

Variables That Affect Immune System Function • Age and gender • Nutrition • Presence of conditions and disorders: cancer/neoplasm, chronic illness, autoimmune disorders, surgery/trauma • Allergies • History of infection and immunization • Genetic factors • Lifestyle • Medications and transfusions: see Table 50-6 • Pyschoneuroimmunologic factors

Tests to Evaluate Immune Function • • • • • • • • •

WBC count and differential Bone marrow biopsy Humoral and cellular immunity tests Phagocytic cell function test Complement component tests Hypersensitivty tests Specific antigen–antibody tests HIV infection tests See Chart 50-3

Assessing for Immune Dysfunction Be on the alert for the following Sx and Sy RESPIRATORY ● Changes in respiratory rate ● Abnormal lung sounds ● Cough (dry or productive) ● Rhinitis ● Bronchospasm ● Hyperventilation CARDIOVASCULAR ● Hypotension ● Vasculitis ● Tachycardia ● Anemia ● Dysrhythmia GIT ● Hepatosplenomegaly ● Vomiting ● Colitis ● Diarrhea

Inflammation: Cellular response to an injury – Is a defensive reaction intended to neutralize, control, or eliminate the offending agent and to prepare the site for repair. – A nonspecific response meant to serve a protective function GENERAL SEQUENCE OF EVENTS: - changes in microcirculation (vasodilation, vascular permeability, and leukocytic cellular infiltration - cardinal signs of inflammation ● redness (rubor) ● warmth (calor) ● edema (tumor) ● pain (dolor) ● loss of function

Chemical Mediators of Inflammation: 1. Histamines - present in many tissues - release by mast cells - responsible for early changes in vasodilation and vascular permeability

2. Kinins - increase vasodilation and vascular permeability - attracts neutrophils

3. Prostaglandins - thought to have a role in increasing tissue permeability

Types of Inflammation: 1. Acute - local vascular and exudative changes - usually lasts less than 2 weeks - “immediate and serves as a protective response” 2. Subacute - includes elements of exudative phase of the acute response and elements of repair - “not widely used term” 3. Chronic - injurious agent persist and the acute response is perpetuated - symptoms lasts for many years - debilitating and can produce long lasting effects - cycle of cellular infiltration, necrosis, and fibrosis begins, with repair and breakdown occur simultaneously - scarring- permanent damage

Cellular Healing: •

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Regeneration - gradual repair of the defects occurs by proliferation of cells of the same type as those destroyed. -Type s of Cells: 1. labile – multiply constantly to replace cells worn out by physiologic process (e.g., epithelial cells lining the GIT and skin) 2. permanent – the nerve cell bodies 3. stable – have latent ability to regenerate, are not shed and do not replacement under physiologic condition - if destroyed they are able to regenerate (kidney, liver, pancreas) Replacement 1. Primary intention healing – wound is clean and dry, edges are approximated (surgical wound) - little scar and healing takes about a week 2. Secondary intention healing – wound defect is larger and gaping, with necrotic and dead material. - wound fills with granulation tissue from bottom upwards - process of repair is longer, more scar with loss of function