Immune System Chapter 43

Slide 2 of 39 2 Types of Immunity  2 major kinds of defenses have evolved to counter threats of viruses, bacteria, & other pathogens  Innate Immunity  Present PRIOR to exposure  Effective from time of birth  Nonspecific  Acquired Immunity  Present only AFTER exposure  Highly specific

Slide 3 of 39

Slide 4 of 39 Innate Immunity  Barrier Defenses  Cellular Innate Defenses  Inflammatory Response  Natural Killer (NK) Cells

Slide 5 of 39 Barrier Defenses  Skin  Provides physical barrier to pathogens  Mucous membranes that cover epithelial linings and surfaces  Physical barrier as well  Secretions that lower skin pH  Lysozymes  Found in tears, sweat, & mucous secretions  Digests bacterial cell walls  Especially effective in eyes & Upper Resp. Tract (URT)

Slide 6 of 39 Cellular Innate Defenses 1. Phagocytic White Blood Cells (WBC) or Leukocytes  Neutrophils  Leukocytes that ingest + destroy microbes (phagocytosis)  Most abundant leukocyte  Chemotaxis attracts neutrophils to infected cells  Competitive_Phagocytosis_Assay_in_Collage n.ogg Competitive_Phagocytosis_Assay_in_Collage n.ogg

Slide 7 of 39

Slide 8 of 39 Cellular Innate Defenses (Page 2)  Eosinophils  Leukocytes that discharge hydrolytic enzymes when in close proximity to parasites (eukaryotic organisms)  Monocytes  Phagocytic leukocytes that develop into macrophages  Macrophages are giant phagocytic cells  Stimulate other immune responses Monocyte

Slide 9 of 39 Summary of Phagocytic WBCs  IF a microbe gets past the barriers, phagocytosis may occur  Ingestion of invading microbes by WBCs called phagocytes  Neutrophils  WBCs that ingest & destroy microbes by phagocytosis  Monocytes  Develop into macrophages (giant phagocytic cells)  Eosinophils  Leukocytes that defend against parasitic invaders by secreting hydrolytic enzymes on them

Slide 10 of 39

Slide 11 of 39 Cellular Innate Defenses (Page 3) 2. Antimicrobial Proteins  Interferon  Innate defense against viral infections  Alter cells adjacent to viral- infected cells to produce substances that inhibit viral replication  Complement System  Leads to the lysis of invading cells  Also play a role in inflammation & acquired defense

Slide 12 of 39 Inflammatory Response  Tissue damage due to physical injury (trauma) or pathogen entry  This triggers the release of chemical signals which result in an inflammatory response  Histamine – chemical released in response to injury  Stored in Mast Cells (mastocyte) (found in connective tissues)  Trigger the dilation and permeability of nearby capillaries  Delivers clotting agents & phagocytic cells to the injured area  Fever & septic shock

Slide 13 of 39  e&q=inflammatory+response&um=1&ie=UTF- 8&ei=OweUS6ChJoS0tgfrhsTUCg&sa=X&oi=video_resul t_group&ct=title&resnum=10&ved=0CDAQqwQwCQ# e&q=inflammatory+response&um=1&ie=UTF- 8&ei=OweUS6ChJoS0tgfrhsTUCg&sa=X&oi=video_resul t_group&ct=title&resnum=10&ved=0CDAQqwQwCQ#  Videos 2 & 4

Slide 14 of 39 1.Chemical signals (like histamines) released by macrophages & mast cells at the injury site 2.Nearby capillaries dilate & become more permeable 3.Clotting begins 4.Chemokines attract more phagocytic cells from the blood to the injury site 5.Neutrophils & macrophages phagocytose pathogens & cell debris

Slide 15 of 39 -itis = Inflammatory Response  Appendix  appendicitis  Pancreas  pancreatitis  Meninges  meningitis  Liver  hepatitis  Joints  arthritis  Septic shock – overwhelming inflammatory response (systemic)  High fever + Low BP  Most common cause of death in critical care units (CCUs)

Slide 16 of 39 Natural Killer (NK) Cells  4 th type of innate immunity  Patrol the body and attack virus- infected body cells  Also attack cancerous cells  Recognize & remove diseased cells  NK releases chemicals that lead to apoptosis  Apoptosis = programmed cell death

Slide 17 of 39 Acquired Immunity  Lymphocytes provide SPECIFIC defenses  2 nd line of defense  2 Types of Lymphocytes (NOT Leukocytes (WBCs))  B Lymphocytes – B Cells  Proliferate in Bone marrow  Produce antibodies  T Lymphocytes- T Cells  Mature in the Thymus  Helper T-cells (CD4) or Cytotoxic T-cells (CD8)

Slide 18 of 39 Acquired Immunity (Page 2)  Lymphocytes circulate through the blood and lymph  Lymphocytes are concentrated in the spleen, lymph nodes, & other lymphatic tissues  Recognize antigens by antigen-specific receptors on their plasma membranes  Antigen – any foreign molecule that elicits a response by lymphocytes  A lymphocyte may have 100,000 receptors, but all of them are specific for only 1 epitope  Epitope – small accessible part of an antigen

Slide 19 of 39 Antibodies  Produced by B-cells  When secreted, the antibodies are called immunoglobulins  Part of the humoral immune response  Specific to a given antigen

Slide 20 of 39 Epitopes

Slide 21 of 39 Activation  Either B- or T-cells can be activated  Occurs when an antigen binds to a B or T cell  Activation leads to each lymphocyte forming 2 types of clonal cells  Clonal cells are all specific to the antigen  1. Effector cells – combat the antigen  2. Memory cells – Long-lived & bear receptors for the same antigen  Allows for a quick immune response in the FUTURE

Slide 22 of 39

Slide 23 of 39 How do B-cells and T-cells Differ?  B-cell receptors bind intact antigens  T-cells bind antigens presented to them by antigen- presenting cells (APC)  B-cell or T-cell responds to only ONE antigen (Specific)

Slide 24 of 39 MHC Proteins  Immune system’s way of recognizing “self” cells  Major Histocompatibility Complex molecules (MHC)  Every individual is different in their MHC proteins  MHC proteins bind to an antigen and bring it to the cell surface  Called antigen presentation

Slide 25 of 39 MHC Proteins (Page 2)  Two types of MHC proteins  Class 1 MHC – All cells but RBCs  Recognized by cytotoxic T-cells (CD8)  Class 2 MHC – B cells & macrophages  The B cells and macrophages that use Class 2 MHC proteins are called APC (Antigen-presenting cells)  Associated with Helper T-cells (CD4)

Slide 26 of 39

Slide 27 of 39 Immune Response Types  Primary Immune Response  First exposure to an antigen  Lymphocyte activation  Secondary Immune Response  Antigen in encountered again  Rapid & stronger response

Slide 28 of 39

Slide 29 of 39 Acquired Immunity  Humoral Immune Response  Involves the activation and clonal selection of effector B cells  B cells produce antibodies that circulate in the blood  Helper T-cells are also involved in the activation of B cells  Cell-Mediated Immune Response  Activation and clonal selection of cytotoxic T cells  Cytotoxic T cells identify & destroy infected cells

Slide 30 of 39

Slide 31 of 39

Slide 32 of 39

Slide 33 of 39 Notes on Acquired Immunity  Helper T cell (CD4)  Aids in BOTH responses  Class II MHC on an APC activates the Helper T cells  Secrete cytokines which stimulate BOTH Cytotoxic-T-cells and B-cells  CD4 protein holds helper T-cell to class II MHC  Cytotoxic T cell (CD8)  Binds to Class I MHC  Bound together by the CD8 protein

Slide 34 of 39 Comparision  B-cells - produce antibodies (provides humoral immunity)  B-cells produce memory cells and plasma cells  Plasma cells secrete antibodies in huge numbers  Antibodies circulate in blood, then bind & destroy antigen  Cytotoxic T-cells – destroy infected body cells  Helper T-cells – activate both B and T cells

Slide 35 of 39 Antibody Actions  Neutralization – Antibodies bind to pathogen’s surface proteins  Prevents pathogen from entering & infecting cells  Opsonization  Results in increased phagocytosis of the antigen  Lysis  Caused by activation of the complement system

Slide 36 of 39 Immunities  Active Immunity  Body comes in contact with antigens  Actively produces antibodies in response to antigen presentation  Naturally developed immunity after an infection  Vaccination or immunization  Passive Immunity  Individual receives antibodies  Placental transmission of immunoglobulins (Antibodies)

Slide 37 of 39 Show vaccination video  Vaccination Video

Slide 38 of 39 Erythrocyte (RBC) Antigens  A, B, AB, or none  Determined by antigen presence on RBC surface  IF non-self, antibodies will form on the foreign antigens  Destroy transfused RBCs

Slide 39 of 39 Immune System Pathologies  Lupus, Rheumatoid arthritis, and MS  Immune system fails to recognize body cells  Since these cells are detected as foreign, immune system attacks the body’s own healthy cells  HIV – attacks CD4 cells or Helper-T-cells  Allergies – body over-responds to an allergen  IgE – immunoglobulin E  Histamine & other mediators cause vasodilation and other symptoms  Mast cells mediate the histamine production