Chapter 23: The Immune System

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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


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