Chapter 43: The Immune System Disease A departure from health Types: Deficiency diseases Genetic diseases Communicable diseases Contagious disease Infectious disease Host provides metabolic needs of pathogen or parasite

Infectious disease Transmission Types Contact Droplet infection Vector Common vehicle transmission Types Sporadic disease Endemic disease Epidemic disease Pandemic disease

Adaptations of pathogen to resist host defense Cell wall Contain proteins to resist host &/or antibiotics Sticky capsule Counters phagocytosis; increases virulence of pathogen Production of enzymes or metabolic toxins Manipulates host cell’s metabolic structure viruses

Adaptations of the Human Body 1st line of defense Physical shield Skin, mucus, ciliated cells, tears, urine flow, coughing, sneezing, ear wax Chemical shield Stomach acids kill bateria Enzymes (lysozyme) in tears etc. Skin acids 2nd line: inflammatory response Increased blood flow Promotes healing Swelling insulates tissues

Macrophages, neutrophils, Eosinophils, & Dendritic cells Phagocytic activity to engulf pathogen Macrophages: Develop from monocytes Migrate through the body or reside permanently in some organs (i.e. spleen) Neutrophils: Enter infected tissue to engulf microbes Self destruct Eosinophils: Position against multi-cellular parasite & release enzymes to destroy Dendritic cells: Can act like macrophages but are usually involved in acquired immunity

Injured, circulating basophils release histamines & prostaglandins Promotes vasodilation Capillaries become “leaky” Attracts phagocytic cells Neutrophil engulfs bacteria macrophage engulfs neutrophil Infected cells release interferon Stimulate adjacent cells to produce proteins that prevent viral replication Activates phagocytes

3rd line: Immune response Production of Lymphocytes Circulate in blood & lymph Concentrated in spleen, lymph nodes, & lymphoid tissue Each lymphocyte is specific to a particular foreign antigen Originate in stem cells of bone marrow Types: B cells Mature in bone marrow T cells Mature in thymus gland Maturing B cells & T cells tested for self-reactivity & destroyed if self reactive

Production of specific antibodies by lymphocytes Antitoxins Neutralize bacterial toxins Agglutinins Clumping of bacteria Opsonins Stimulate phagocytosis of clumped bacteria Lysins Dissolve cell walls of bacteria Precipitins Coagulation chemicals of bacteria

Immunoglobins (antibodies) Specific antigen binding immunoglobulins Generated by B cells Types IgM First antibodies to arrive at infection site IgC Most abundant antibodies in blood & lymph IgA Antibodies found in body secretions (saliva, sweat) IgE Trigger release of histamines & other chemicals by mast cells & basophils to cause allergic reactions IgD On naïve B cells (not yet exposed to foreign antigen) Receives antigen that leads to clonal selection

Self/non-self Immune system must be able to distinguish foreign from non-foreign proteins Major histocompatability complex (MHC) Group of glycoproteins embedded in cell membrane Two major classes of MHC Class I MHC Bind to cytotoxic T cells Class II MHC Known as antigen presenting cells Bind to specialized cells (macrophages, B cells) & activate T cells

Action of lymphocytes Humoral Response B cells Helper T cells Enter blood & produce specific antibodies to counter specific antigens Antigen-antibody complexes are formed Helper T cells Secrete interleukins Stimulate clonin of B cells to memory cells B cells into memory cells (M cells) Long lived cells Recognize specific antigen Basis of active immunity Plasma cells (P cells) Short lived cells Produce additional antibodies with initial exposure to antigen Antibodies draw phagocytic cells in to destroy

Cell mediated response Cytotoxic T cells Stored in thymus gland prior to moving into blood Activated when CD8 receptors recognize antigen on Class I MHC; helper T cell releases cytokines to promote activation Do not produce antibodies Attack & kill antigen-bearing cells Secrete proteins that destroy infected cells Stimulate the production of B cells Dispose of infected cells Suppress B cell reproduction when infection has been suppressed Secrete interferon which defends healthy cells from virus

Primary vs. Secondary immune response Primary immune response First exposure or vaccination to antigen Results in formation a specific antibody to inactivate an antigen Requires time to occur Secondary immune response Rapid reproduction of specific antibodies to inactivate & destroy antigen (immediate)

Types of Defense Innate immunity Acquired immunity/adaptive immunity Present at birth without any exposure Non-specific Acquired immunity/adaptive immunity Develops after exposure Highly specific Recognition by lymphocytes

Types of immunity Natural immunity Active immunity Inherited immunity (parent to child) Active immunity Long term immunity due to Exposure (i.e. chicken pox, mumps, measles) Vaccination Intentional exposure to weakened/dead pathogen or pathogenic toxin Immunization Polio...

Passive immunity Borrowed or temporary immunity through Injection of antibodies Blood serum or gamma globulin injections Immediate immunity Short term immunity Memory cells are not produced

Blood Groups effect on transfusions & transplants Antibodies present against non-self blood types without exposure result of reaction to bacterial antigens MHC molecules stimulate immune response leading to tissue rejection each person has a unique polymorphic combination of MHC molecules

Exaggerated, self-directed or diminished immune response & disease Allergies Hypersensitive response to antigens on allergens Often involve IgE antibodies Attach to mast cells to induce histamine release Anaphylactic shock Whole body, life threatening allergic reaction Autoimmune disease Body generates antibodies against self Ex. Lupus, rheumatoid arthritis, multiple sclerosis, diabetes mellitus

Immunodeficiency diseases Inborn or primary Caused by genetic or developmental defect Defect in production of immune cells or specific proteins Acquired or secondary Develops later in life Caused by exposure to agents or disease Ex. Hodgkin's, AIDS