Lecture 9 : Immunity, Disease, and Vaccines Objectives: Understand how the body fights infections Defense strategies Components of the defense Understand how pathogens fight the defense Understand how a vaccine works Objectives: Understand how the body fights infections Defense strategies Components of the defense Understand how pathogens fight the defense Understand how a vaccine works Background Reading: Chapter 35

Three Lines of Defense Barriers at Body Surfaces Physical barriers Chemical barriers Normal flora Disposable surfaces Nonspecific Responses (Innate Immunity) Inflammation –Fast acting cell types (self vs. non-self) –Cells that remove debris –Proteins: hole plugging, hole making, and cutting tools Specific Immune Responses (Cellular Immunity) B and T cells Communication Antibodies and perforins

Barriers at Body Surface Intact skin and mucous membranes Lysozyme Normal bacterial flora Flushing and Sheading

Three Lines of Defense Barriers at Body Surfaces Nonspecific Responses (Innate Immunity) Inflammation –Fast acting cell types (self vs. non-self) –Cells that remove debris –Proteins: hole plugging, hole making, and cutting tools Specific Immune Responses (Cellular Immunity)

Nonspecific Responses Lymph nodes trap and kill pathogens Natural killer cells attack a range of targets Inflammation Fast acting cell types (self vs. non-self) Cells that remove debris Proteins: hole plugging, hole making, and cutting tools

Complement System Plasma proteins that take part in both specific and nonspecific response Activation of one triggers cascade of reactions that activate others CASCADE REACTION FORMATION OF ATTACK COMPLEXES LYSIS OF TARGET

Acute Inflammation Nonspecific response to foreign invasion, tissue damage, or both Destroys invaders, removes debris, and prepares area for healing Characterized by redness, swelling, warmth, and pain

Inflammation Mast cells release histamine Capillaries dilate and leak Complement proteins attack bacteria White cells attack invaders and clean up

Inflammation Redness- vessel dilation Warmth- increased blood flow Swelling- edema, leaking Pain- pressure on free nerve endings

Three Lines of Defense Barriers at Body Surfaces Nonspecific Responses (Innate Immunity) Specific Immune Responses (Cellular Immunity) B and T cells Communication Antibodies and perforins

Immune Responses Directed against specific invaders Carried out by T cells, B cells, and macrophages Communication signals such as interleukins play a vital role

Definitions: B cells, T Cells, and Macrophage B cell –Covered with antibody (one type) –Don’t recognize MHC presented antibody, only free antigens T Cell (Thymus) –I gnore free antigen –recognize only antigen presented by MHC Macrophage –Clears particles –Presents MHC antigens

Definitions Antibody Structure Antibody consists of four polypeptide chains Certain parts of each chain are variable; impart antigen specificity variable region of heavy chain antigen-binding site hinge region (flexible) variable region of light chain constant region of light chain

Definitions Antigen: Any substance that stimulates the production of antibodies Usually a protein or large molecule Little 3-D shapes that antibodies can recognize.

Recognition Self and Non-self

antigen framents MHC molecule antigen-MHC complex MHC Recognition Displaying non-self

Features of Immune System Immunological specificity –B and T cells zero in on certain kinds of pathogens; response is pathogen specific Immunological memory –Immune system recognizes and reacts swiftly to a pathogen it has “seen”

Memory and Effector Cells When a B or T cell is stimulated to divide, it produces more than one cell type Memory cells are set aside for future use; they are the basis for immune memory Effector cells engage and destroy the current threat

Key Component of Immune Response MHC markers Antigen-presenting cells Helper T cells Effector cytoxic T cells Natural killer cells B cells

Overview of an Immune Response Naive helper T cell Naive B cell Antigen- presenting cell Activated helper T cell Effector B cell Naive cytotoxic T cell Effector cytotoxic T cell Antibody - mediated response Cell - mediated response Key Components of Immune Response MHC markers Antigen-presenting cells Helper T cells Effector cytoxic T cells Natural killer cells B cells

Lymphocyte Battlegrounds Lymph nodes filter antigens from body fluids Macrophages, dendritic cells, B cell and T cells in nodes and spleen mount a defense

Antibody-Mediated Response Carried out by B cells Targets are intracellular pathogens and toxins Antibodies bind to target and mark it for destruction by phagocytes and complement

Antibody- Mediated Response Naive B cell Antigen- presenting B cell Helper T cell Interleukins Memory B cell Effector B cell secretes antibodies Virgin B cell becomes antigen-presenting B cell Helper T cell binds to antigen-MHC complex on the B cell Interleukins stimulate B cell division and differentiation Effector cells secrete antibodies

5 Classes of Immunoglobulins IgM are secreted first; trigger complement reactions, agglutination IgD function is not understood IgG activates complement; can cross placenta IgA associates with mucus-coated surfaces IgE triggers inflammation

Cell-Mediated Response One macrophage Another macrophage interleukins Helper T cell Cytotoxic T cell Infected body cell Carried out by T cells Stimulated by antigen- presenting macrophages Main target is antigen- presenting body cells (cells with intracellular pathogens) or tumor cells

Organ Rejection Cytotoxic T cells can contribute to rejection of transplanted tissue They recognize a portion of the donor cell’s MHC complex as self, view a portion as foreign Treat the combination as an antigen- MHC complex and attack donor cells

Allergies Immune reaction to a harmless substance Genetic predisposition IgE responds to antigen by binding to mast cells and basophils These cells secrete the substances that cause symptoms

Anaphylactic Shock A life-threatening allergic reaction Caused by the release of histamine by many mast cells and basophils Airways constrict and blood pressure drops as capillary permeability soars

Autoimmune Disorders Immune system makes antibodies against self antigens Grave’s disease Myasthenia gravis Rheumatoid arthritis

Bacterial Pathogen Category A Threats: Defined by the CDC as high-priority agents include organisms that pose a risk to national security because they: –C an be easily disseminated or transmitted from person to person –R esult in high mortality rates and have the potential for major public health impact –M ight cause public panic and social disruption –R equire special action for public health preparedness.

Infection typeMortality (untreated) Cutaneous 20% Intestinal80-90% Inhalation90*-99% *with treatment Bacillus anthracis

Major Symptoms Skin- –characteristic sores Intestinal- –fever, intestinal discomfort, intestinal ulceration. Inhalation- –fever, cough, malaise (flu-like) –Sever respiratory distress, chills, edema

Pathophysiology

Immunization Process that promotes immunity Active immunization - –Antigen-containing material is injected –Confers long lasting immunity Passive - –Purified antibody is injected –Protection is short lived

first exposure to antigen subsequent exposure to the same antigen Immunization

HIV Picture

All you need to know Chapter 35 Table 35.1 Table 35.1 figure 35.5 Figure 35.6 Figure 35.7