Chapter 23: The Immune System
Which type of humoral immunity occurs when you receive a vaccine?
Active -- Artificial
What do plasma cells secrete?
Antibody molecules
Which cells of the immune system give rise to plasma cells?
B cells
Lysozyme
Breaks down bacterial cells walls
What is opsonization?
Coats pathogen surfaces
What are the 3 types of cells that act as APCs?
Dendritic cells Macrophages B cells
What is complement?
Group of ~20 plasma proteins that circulate in inactive form
Which type of immunity acts against extracellular targets such as bacteria and free viruses?
Humoral
What is a pathogen?
Invading disease-producing microorganisms
The release of inflammatory chemicals has two immediate effects on blood vessels in the injured area. What are these effects and what do they accomplish?
Localized vasodilation -- increased blood flow to the area; redness and heat Increased capillary permeability -- fluid and plasma proteins leak into tissue spaces; swelling and pain
What is the third line of defense against disease?
Lymphocytes
Phagolysosome
Lysosome fuses with phagocytic vesicle
Soon after inflammation begins, phagocytes are mobilized to the injured site. Which phagocytes arrive later? What is their role?
Macrophages Replace neutrophils and clear area of debris
How does opsonization enhance phagocytosis?
Marks antigen for immune response
What are the two ways of acquiring active humoral immunity?
Naturally -- response to infection Artificially -- vaccine containing dead/attenuated pathogens
4 Mechanisms Used by Antibodies to Bring About Destruction to a Pathogen
Neutralization -- antibodies block specific sites on virus/bacterial toxins; prevents binding to receptor on tissue cells Agglutination -- antibodies bind to more than one cell-bound antigen at a time -- clumping Precipitation -- soluble molecules are cross-linked; settle out of solution Complement fixation -- antibodies bind to target cell membrane; activates complement
What are the two major types of phagocytes?
Neutrophils Macrophages
Soon after inflammation begins, phagocytes are mobilized to the injured site. Which phagocytes arrive at the injured area first? What is their role?
Neutrophils Release cytokines to amplify inflammation
What is the function of natural killer cells?
Nonspecifically destroy virus-infected cells and cancer cells before adaptive immune system is activated
When does the primary immune response occur?
On first exposure to an antigen
How do helper T cells help with humoral immunity?
Secrete cytokines to activate B cells
How do helper T cells help with cellular immunity?
Secrete cytokines to activate CD8 cells, amplify innate defenses
What are the surface barriers that make up the body's first line of defense?
Skin and mucous membranes
Regulatory T Cells
Suppress immune responses
Mucus
Traps dust, debris, and microbes
Steps of B Cell Activation
1. Antigen binding to a receptor on a specific B cell 2. Proliferation of B cells to form a clone 3. Differentiation of plasma cells and memory B cells 4. Secretion of antibodies
Where do B cells mature?
Bone marrow
What is a self-antigen?
Cell surface proteins that identify the cell as "self"
Which type of immunity acts against cellular targets such as virus-infected tissue cells, cancer cells, and cells of transplanted tissues?
Cellular
Which type of immunity is provided by lymphocytes?
Cellular
What is the role of antigen-presenting cells in adaptive immunity?
Engulf, process, and display antigens on their surfaces
Helper T Cells
Enhance activity of other immune cell 60-80% of circulating T cells
Activation of complement on the membrane of a target cell has three effects:
Enhances inflammation Promotes phagocytosis Causes cell lysis of the target cell
What is the first line of defense against disease?
Epithelial barriers
What causes pain?
Increased capillary permeability
Class I MHC Proteins
On all nucleated cells Display endogenous antigens -- synthesized inside the cell Recognized by cytotoxic T cells
What happens to clone cells that do not become plasma cells? What is the function of these cells?
They become memory cells Respond to later encounter with same antigen
What is the function of interferons?
They interfere with replication of viruses in nearby cells that have not yet
Where do T cells mature?
Thymus
What are the main targets of cytotoxic T cells?
Virus-infected cells Cells with intracellular bacteria/parasites Cancer cells Transplanted cells
Under what conditions would you expect a cell to secrete interferons?
When a cell is infected with a virus
How does active humoral immunity differ from passive humoral immunity?
Active -- B cells encounter antigens and produce antibodies Passive -- Ready-made antibodies introduces into body; B cells not challenged by antigens; no immunological memory
Which type of humoral immunity occurs when you catch the flu from your roommate?
Active -- Natural
Which type of humoral immunity provides immunological memory?
Active humoral
What is the membrane attack complex? What is the effect on the target cell?
Assembly of complement proteins that embeds in a plasma membrane of target cell to create a pore Influx of water -- lyses cell
Which type of lymphocyte is responsible for humoral immunity?
B lymphocytes
What begins the inflammatory process?
Bacterial infection, tissue injuries
Why is a moderate fever beneficial?
Causes the liver and spleen to sequester iron and zinc Less available for bacterial growth Increases metabolic rate of tissue cells Speeds up repair
Cytotoxic T Cells
Directly attack and destroy host cells bearing a foreign antigen
Which type of immunity is provided by antibodies?
Humoral
What are the two types of adaptive immunity?
Humoral -- antibody mediated Cellular -- cell mediated
How do antigens bound to I MHC proteins allow cytotoxic T cells to identify body cells that have become infected or are cancerous?
In infected cells, class I MHCs display foreign antigens or abnormal cancer proteins Destroyed by cytotoxic T cells
What causes swelling?
Increased capillary permeability
What distinguishes the innate (nonspecific) defense system from the adaptive (specific) defense system?
Innate -- responds immediately; defends against foreign/abnormal material on initial exposure Adaptive -- selectively targets particular foreign material to which the body has already been exposed; longer time
What is the second line of defense against disease?
Internal defenses
Acid
Kills microbes
What is an antigen?
Large, complex molecule that triggers a specific immune response against itself when it gains entry into the body
Phagocyte Mobilization Steps
Leukocytosis -- increase in number of neutrophils in blood in response to leukocytosis-inducing factors Margination -- neutrophils stick to endothelial lining Diapedesis -- neutrophils squeeze between endothelial cells Chemostaxis -- neutrophils migrate up gradient of chemotaxins to injury sites
What causes heat?
Localized vasodilation
What causes redness?
Localized vasodilation
What are the two ways of acquiring passive humoral immunity?
Naturally -- antibodies delivered to fetus via placenta or to infant through milk Artificially -- injection of antibodies from immune donor
Class II MHC Proteins
Only on the surface of APCs Display exogenous antigens -- from outside the cell Recognized by T helper cells
Which type of humoral immunity occurs when antibodies pass from a mother to a fetus or infant?
Passive -- Natural
Which type of humoral immunity occurs when you receive an injection of antibodies after exposure to a disease such as rabies?
Passive -- artificial
Phagosome
Phagocyte forms pseudopods that engulf particles
What are the five categories of internal innate defenses?
Phagocytes Natural killer cells Inflammation Antimicrobial proteins Fever
Cilia
Push pathogens trapped in mucous out of trachea to prevent entry into lungs
When does the secondary immune response occur?
Re-exposure to the same antigen
What is the importance of immune surveillance? What two cells are responsible for it?
Recognition and destruction of newly arisen cancer cells Cytotoxic T cells and NK cells
What does it mean to say that adaptive immunity is "specific"?
Recognizes and targets particular foreign agents
How do helper T cells assist with the innate defenses?
Recruit neutrophils and macrophages to infection site Activate macrophages to become more potent
Where do all lymphocytes originate from?
Red bone marrow
What are the four cardinal signs of inflammation?
Redness Heat Swelling (edema) Pain
What are pyrogens?
Released by leukocytes and macrophages Act on body's thermostat to raise temperature
How do cytotoxic T cells use perforins and granzymes to attack and kill their target cells? What other immune cells use this killing mechanism?
Releasing perforin forms pore like channels in target cell membrane. Granzymes enter target cell and trigger apoptosis NK cells
Three characterizations of the adaptive immune response that distinguish it from the innate defenses
Specific -- recognizes and targets particular foreign antigens Systemic -- not confined to initial infection site Memory -- after initial exposure, mounts stronger attacks
Which type of lymphocyte is responsible for cellular immunity?
T lymphocytes
What are the four classes of pathogens?
Viruses Bacteria Fungi Parasites
