THE IMMUNE SYSTEM (LECTURE 13) Flashcards
What are the two types of immunity that make up our immune system?
Innate immunity and adaptive immunity.
Characterize innate immunity. What elements make up innate immunity? (3)
Non-specific and fast response (physical and chemical barriers and internal defenses)
List 3 internal defenses that make up the innate immunity.
WBCs (phagocytic and non-phagocytic), antimicrobial peptides and inflammatory response.
Characterize adaptive immunity (acquired immunity).
Specific and slower response, humoral and cell-mediated response.
What is the immune system’s first line of defense?
Physical and chemical barriers.
What are the immune system’s physical and chemical barriers?
Skin, mucous membranes, sweat, saliva, tears and mucous.
Provide an example of a mucous membrane.
The lining of digestive, respiratory and genitourinary tract.
How does sweat defend against pathogens?
Sweat contains acids that inhibit bacterial growth.
How do saliva, tears and mucous defend against pathogens?
These wash away pathogens and contain lysozyme to destroy bacterial cell walls.
What is the immune system’s second line of defense?
The inflammatory response.
When does the inflammatory response occur?
When tissue is damaged or microorganisms enter (or both).
Damaged cells or microorganisms release chemicals that: (4)
Increase permeability and blood flow and bring clotting factors and phagocytic cells to the site.
What is the visible result of chemicals released due to damaged cells or microorganisms.
Swelling, redness and heat.
What 3 primary chemicals are released by damaged cells?
(1) Histamines (2) Prostaglandins (3) Cytokines
Describe phagocytic white blood cells.
They ingest invading microbes.
Name 2 phagocytic white blood cells.
(1) Neutrophils and (2) Macrophages.
Are macrophages part of innate or adaptive immunity?
They participate in both.
Name 3 non-phagocytic white blood cells.
Eosinophils, mast cells and natural killer cells (NK).
What do eosinophils do?
These release chemicals to destroy parasites.
What do mast cells do?
They release histamine.
What do natural killer cells do?
They destroy virus-infected cells and cancer cells by causing cell lysis.
Name 2 (types of?) antimicrobial peptides.
Complement and Interferon.
Describe complement antimicrobial peptides.
> 30 serum proteins and are involved in a cascade of steps which lead to cell lysis of a bacterium or an infected cell (by poking holes in membrane).
Describe interferon antimicrobial peptides.
These are secreted by virus infected cells and they prevent cell-cell spread of the virus and inhibits viral reproduction.
What are the 2 branches of adaptive / acquired immunity.
(1) Humoral and (2) Cell mediated immune response.
What are the key players in adaptive immunity? (4)
Antigens, antibodies, lymphocytes and antigen presenting cells.
What are the 2 types of lymphocytes?
B-cells and T-cells.
What are the 2 types of B-cells?
Plasma cells and memory B-cells.
What are the 2 types of T-cells?
T-helper cells and cytotoxic T-cells.
Name 3 cells that can act as antigen presenting cells.
Macrophages, dendritic cells, B-cells.
What are antigens?
These are proteins or polysaccharides that elicit an immune response - pieces of pathogen.
Are all antigens the same in structure? What does this entail?
No, each type of antigen has a unique structure that a specific T-cell or B-cell receptor will bind to.
Where are antigens found? (7)
On the surface of viruses, virus-infected cells, bacteria, fungi, protozoa, pollen or transplanted tissue.
What do lymphocytes do?
They mediate specific immune responses.
Describe B-cells. (3)
They mature in bone marrow, they produce antibodies and they effect the humoral response.
Describe T-cells. (2)
They mature in thymus and effect the cell-mediated response.
Describe plasma cells.
These are effector B-cells that produce antibodies.
Describe memory B-cells. (what do they have / what do they do?)
These have antigen receptors - they recognize antigens through binding.
What are antibodies? What else are they called?
These are Y-shaped proteins that are also called immunoglobulins.
What are antibodies comprised of?
4 polypeptide chains (2 identical light chains and 2 identical heavy chains).
What is each polypeptide chain that makes up an antibody composed of?
Each chain is composed of a variable region and a constant region.
Describe the variable region of an antibody’s polypeptide chain.
It is an amino acid sequence that varies from antibody to antibody. It binds to a specific antigen.
What is the constant region of an antibody’s polypeptide chain involved in?
It is involved in antigen disposal.
Describe cytotoxic T-cells.
These release perforin and granzymes to kill infected cells.
Describe helper T-cells.
These release chemicals to activate other cells.
Clonal selection is a response to…
to the entry of pathogen.
Clonal selection occurs for…
both T-cells and B-cells.
What are the steps of clonal selection? (3)
(1) Antigen enters body and lymphocyte with matching receptor binds to the antigen. (2) Lymphocyte becomes activated. (3) Two clones are produced.
What does the activation of a lymphocyte in clonal selection entail? (step 2)
The lymphocyte divides and differentiates to produce thousands of cells specific for that antigen.
What two clones are produced in step 3 of clonal selection?
Effector cells and memory cells.
Describe effector cells produced in step 3 of clonal selection.
These are short lived and actively destroy antigens.
Describe memory cells produced in step 3 of clonal selection.
These are long-lived and will respond to future entry by the same antigen.
Memory cells are an example of ____ memory.
Memory cells are an example of immunological memory.
What do antigen presenting cells (APCs) do?
These phagocytize pathogens and present antigen fragments on their surface.
Where are antigens presented on antigen presenting cells?
Antigens are presented within MHC II.
MHC is an abbreviation for what?
Major histocompatibility complex.
What is the purpose of MHC?
It is important for T-cells to recognize and bind to antigens and become activated. It presents the antigen.
Differentiate the 2 types of MHC.
Class I is present on most nucleated cells. Class II is present on antigen presenting cells only.
Cytotoxic t-cells interact with cells expressing ____.
Cytotoxic t-cells interact with cells expressing MHC I + antigen.
Helper t-cells interact with cells expressing ____.
Helper t-cells interact with cells expressing MHC II + antigen.
Describe the humoral response. (3)
B-cells specific for an antigen are activated to make plasma cells. Plasma cells produce antibodies that are also specific for the antigen. Antibodies bind to free, intact antigens in body fluids.
How are B-cells activated?
By binding to antigen and then being activated by a T-helper cell that has the same antigen receptor.
By what 3 methods do antibodies dispose of antigens?
Neutralization, opsonization and complement fixation.
Describe neutralization. (2)
Antibodies block viral attachment and coat bacteria to enhance phagocytosis (opsonization).
Describe opsonization.
It is the clumping of viral particles or bacterial cells to enhance phagocytosis.
Describe complement fixation.
The binding of an antibody to a cell initiates complement cascade which results in cell lysis.
Summarize the cell-mediated response.
Cytotoxic T-cells specific for an antigen are activated to destroy cells containing the antigen (infected cells).
What causes cytotoxic T-cells to mediate an immune response? (3)
(1) Intracellular antigens (presented on MHC), (2) fungi, protozoa, parasitic worms and (3) Transplanted tissues and cancer cells.
List the steps of the cell-mediated response.
(1) Infected cells express antigen on their surface via MHC I. (2) Activated cytotoxic T-cells bind to antigen-MHC I complex. (3) Cytotoxic cells is activated and releases chemicals to kill the infected cell.
How is the interaction between activated cytotoxic T-cells and antigen-MHC I complex in the cell mediated response enhanced?
The interaction is enhanced by CD8 accessory protein on cytotoxic cells.
What do cytotoxic T-cells release to kill infected cells?
Perforin and granzymes.
Humoral and cell mediated pathways are linked by what?
By T-helper cells.
List the steps of the overall adaptive immune response. (3)
(1) APC phagocytizes the pathogen and presents antigen on its surface cradled within MHC II. (2) Helper T-cell with correct receptor interacts interacts with antigen/MHC II. (3) Two clones of the T-helper cell are produced.
In the overall adaptive immune response, what enhances the interaction between a helper T-cell with correct receptor and antigen/MHC II?
Interaction is enhanced by CD4, an accessory protein on helper T-cells.
What are the two clones of the T-helper cell produced in the final step of the overall adaptive immunity response?
Effector cells and memory T-cells.
Describe the effector cells produced at the final step of the overall adaptive immune response.
They secrete interleukin 2 (IL-2), a cytokine which activates B-cells, cytotoxic T-cells and helper T-cells.
Describe the memory T-cells produced produced in the final step of the overall adaptive immune response.
These are ready to respond to a subsequent exposure.
Name the responses related to immunological memory (immunity).
First response, second response, primary response and secondary response.
Describe the first response of immunological memory.
Only 1 of each cell that is specific for an antigen needs to be activated to produce more.
Describe the second response of immunological memory.
Many memory cells are available and ready to activated.
Describe the primary response of immunological memory.
First exposure to antigen, antibody concentration peaks 10-17 days after exposure and after this response, memory cells stick around for next exposure.
Describe the secondary response of immunological memory.
Memory cells are activated, antibody concentration peaks 2-7 days after exposure and more effector cells are produced faster.
Describe the types of immunity in terms of how they’re acquired and their “activity”.
Immunity can be achieved naturally or artificially and can be active or passive.
Describe active immunity.
Immunity conferred by recovery from an infectious disease (immune memory). Depends on an individual’s own immune system.
How does one naturally obtain active immunity?
By recovering from an infectious disease.
How does one artificially obtain active immunity?
By vaccination.
What’s another word for passive immunity?
Borrowed immunity.
Describe passive immunity.
Antibodies are transferred from one individual to another (immunity does not last).
Provide an example of naturally obtained passive immunity.
When mother transfers antibodies to the fetus across the placenta or to the infant while nursing. This temporary protection can last for weeks to months.
Provide an example of artificially obtained passive immunity.
Injection of antibodies into an individual, such as rabies antibodies to protect against rabies.
Describe vaccines.
These are weakened versions of pathogens that do not cause disease but can induce an immune response.
Vaccines give you ____ ____ without….
Vaccines give you immune memory without making you sick.
Provide examples of weakened versions of pathogens used in vaccines. (3)
Inactivated toxin, killed microbe or parts of a microbe.
What anomaly lead to the discovery of the first the first vaccine? In what year?`
Milkmaids exposed to cowpox were immune to smallpox (1796).
Can we get sick by the same virus more than once? Explain.
Yes. For example, we get the flu more than once because different viruses (strains of viruses) cause the flu.
What are allergies?
Hypersensitivities of the immune system to an allergen after an initial exposure caused an immune response.
Describe the development of an allergy.
Upon first exposure to allergen, IgE antibodies are made (specific for that allergen). IgE antibodies will bind to receptors on mast cells and upon subsequent exposure, allergen interacts with antibodies on mast cell and triggers the release of histamine. Mast cells with attached antibodies will circulate in the blood and react quickly with allergen upon subsequent exposures.
Name 3 abnormal functions of the immune system.
Allergies, autoimmune disorders and immunodeficiencies.
Describe autoimmune disorders.
When the immune system attacks itself - failure to recognize itself!
Provide 4 examples of autoimmune disorders and the area of the body they affect.
Rheumatoid arthritis (joints), multiple sclerosis (myelin sheath), lupus (many tissues) and diabetes (beta cells in the pancreas).
Immune system is normally ____-____.
Immune system is normally self-tolerant.
Errors in what process leads to autoimmune disorders?
Lymphocytes bearing antigen receptors for self-molecules are destroyed. Errors in this process leads to autoimmune disease.
Immunodeficiency is when…
an individual is deficient in either humoral or cell mediated defenses (or both).
Name 3 examples of immunodeficiencies.
Severe combined immunodeficiency (SCID), Hodgkin’s disease and acquired immunodeficiency syndrome (AIDS).
Describe severe combined immunodeficiency (SCID).
It is when both the humoral and cell mediated defenses are non-functional.
Describe Hodgkin’s disease.
Due to cancer in the lymph system (primarily B-cells) - this cancer results in the production of so many unhealthy lymphocytes that it hinders the body’s ability to make healthy lymphocytes.
Describe acquired immunodeficiency syndrome (AIDS).
It is a lethal disorder caused by HIV. HIV specifically infects helper T-cells by binding to the CD4 receptor on the surface, causing a reduction in the number of helper T-cells.
I am a lymphocyte that binds to a specific antigen within an MHCII complex.
Helper T-cell.
I am a lymphocyte that binds to a specific antigen within an MHCI complex.
Cytotoxic T-cell.
I am a lymphocyte that releases perforin to cause cell lysis.
Cytotoxic T-cell.
I am a lymphocyte that binds to specific antigens that are free in the fluids of the body (i.e. not presented within an MHC complex).
B-cell.
I produce antibodies.
Plasma cell.
I have an MHC II complex on my cell surface.
APC (B-cell, macrophage, dendritic cell).
I have an MHC I complex on my cell surface.
All nucleated cells.
I activate B-cells and T-cells that have the same antigen receptor as me by releasing cytokines.
Helper T-cells.
I am a lymphocyte that mediates the humoral response.
B-cell.
I am a lymphocyte that mediates the cell-mediated response.
Cytotoxic T-cell.
I am a protein or polysaccharide that lymphocytes react against.
Antigen.
I am a white blood cell that acts in innate immunity.
Macrophage, neutrophil, eosinophil, mast cell, NK-cell.
I am a lymphocyte that is ready to act upon subsequent exposure to the same antigen.
Memory cell.
I produce histamine when activated by an allergen.
Mast cell.
