The Immune System
Body Defenses · 2 intrinsic systems 1. innate (nonspecific) defenses does not discriminate between one threat or another first line of defense - skin and Ch. 21 mucous membranes second line of defense - phagocytes, NK cells, inflammation, antimicrobial proteins, fever 2. adaptive (specific) defense The Immune System protect against specific threats Ch. 21 third line of defense - B and T cells
Innate Defenses Surface Barriers · prevent the approach, deny the entrance, or limit · skin, mucous membranes and their secretions the spread of pathogens · keratin resistant to microorganisms, weak acids/bases, harmful or disease-causing microorganisms bacterial enzymes, and toxins · present at birth nicks and cuts allow organisms to invade · rapid response (same every time) · mucous membrane secretions acidic secretions - sweat, sebum, vaginal secretions, tears HCl - stomach saliva - contains lysozyme mucus - respiratory and digestive systems
Internal Defenses Internal Defenses · phagocytes - move between cells and recognize · antimicrobial proteins chemical antigens that stimulate phagocytosis interferons - proteins released from virus-infected carried out by macrophages (type of monocyte) and cells that trigger the production of antiviral proteins neutrophils that interfere with viral replication inside healthy · natural killer (NK) cells - lymphocytes that "polices" the cells; mobilize the immune system body looking for cells lacking "self" antigens complement - lyses microorganisms, enhances induce apoptosis (programmed cell death) and phagocytosis, intensifies inflammatory and immune release chemicals that enhance inflammation (cytokines) responses · inflammation - triggered by physical trauma, intense heat, irritating chemicals, or infection by viruses, · fever - abnormally high temperature fungi, or bacteria initiated by pyrogens (chemicals released by leukocytes and macrophages) 4 cardinal signs - redness, heat, swelling, pain prevents the spread of damaging agents to nearby high body temp inhibits microbial multiplication (iron tissues and zinc stored in liver) and enhances body repair disposes of cellular debris and pathogens processes prevents movement to encourage healing/repair The Immune System
1 All of the following are innate defenses 2 MATA: Which innate defenses involve EXCEPT an increase in temperature? A complement proteins A complement B inflammation B fever C mucous membrane secretions C inflammation D antibodies D interferons E NK cells
3 Innate defenses, like fever and Adaptive Defenses · characteristics interferons, are nonspecific and specificity - recognizes and reacts to specific antigens acquired throughout our lifetime. versatility - not restricted to the first infection memory - mounts stronger attacks on "remembered" antigens True tolerance - can ignore "self" antigens · types False cell-mediated immunity (T cells) - cells killing cells antibody-mediated (humoral) immunity (B cells) - antibodies mark pathogens for destruction
Cell-Mediated Immunity · T cells cannot recognize antigens in their natural state; can only recognize processed or internalized antigens · target cells infected by viruses and bacteria, abnormal or cancerous cells, and cells of transplanted foreign tissue · activated T cells release cytokines (chemical messengers), like interferon or interleukins, that amplify and regulate immune responses · T cell differentiation
helper T (TH) - "director" of adaptive immune response activate B cells, T cells, and macrophages, recruit other immune cells to join the fight AIDS destroys helper T cells (no immune response) cytotoxic T (TC) - attack and kill other cells regulatory R (TREG) - suppress response of B and T cells The Immune System
Cell-Mediated Immunity Antibody-Mediated Immunity Antibody-Mediated Immunity · starts with antigen challenge first encounter between an immunocompetent B cell and its antigen; activates B cell immunocompetence - ability to recognize a specific antigen · activated B cells divide and produce plasma cells · plasma cells secrete antibodies 2000/sec for 4 or 5 days · antibodies bind with their specific antigen, marking it for destruction form antigen-antibody complexes PLAN: precipitation (falling out of solution), lysis (complement activation), agglutination (clumping), neutralization (blocks toxic effect) · B cells that do not become plasma cells turn into memory B cells memory B cells allows the body to mount an immediate MHC = Major Histocompatability Complex attack when they encounter the same antigen a second time
Primary vs. Secondary Response 4 __ cells are responsible for cell- · primary response - first exposure to a particular antigen mediated immunity, while __ cells are 6-7 day lag time after antigen challenge responsible for humoral immunity. allows B cells for that antigen to replicate and start producing antibodies peak levels around 10 days A T, B · secondary response - subsequent exposure(s) to the same antigen B B, T memory cells recognize the antigen C helper T, cytotoxic T response is faster, longer, and more effective D cytotoxic T, helper T
Antibody Structure MADGE Antibodies · heavy chains - identical to each · antibody = immunoglobulin (Ig) other; more than 400 amino acids · IgM - first antibody released · light chains - identical to each · IgA - found in secretions other; half as long as heavy chains (i.e. mucus, sweat, etc.) · variable region - depends on the antigen · IgD - found on B cell surfaces · constant region - same for all antibodies · IgG - most abundant antibody; · antigen-binding site - variable regions of can cross placenta heavy and light chains; antigen specific · IgE - involved in inflammation and allergic reactions The Immune System
5 Immunoglobulins are antigen-specific Types of Immunity · specific immunity may involve innate immunity and are made during the primary (genetically determined, present at birth) or response. acquired immunity (developed during life) · 2 types of acquired immunity active immunity can be naturally acquired (getting True sick) or artificially acquired (vaccines) passive immunity is produced by the natural transfer False of antibodies (mom's placenta or milk) or artificial transfer of antibodies (donated antibodies that jumpstart your own attack; hepatitis, snake bites, rabies, tetanus)
6 MATA: When I was sick, I spread my Immune Disorders · immunodeficiencies - immune system does not germs every time I coughed. What develop normally or the immune response is blocked type(s) of immunity was I helping you SCID - severe combined immunodeficiency develop by sharing my germs? syndromes; very few B and T cells AIDS - acquired immune deficiency syndrome; results (You're welcome by the way :-)) from HIV infection; attacks CD4 proteins/helper T A acquired cells · autoimmune diseases - immune response mistakenly B innate targets normal body cells and tissues multiple sclerosis (MS), Graves' disease, Type 1 C specific diabetes mellitus, lupus, rheumatoid arthritis · hypersensitivities - excessive reactions to harmless D active threats (allergens) E passive