10.7 Innate and Adaptive Immunity Flashcards
What does the lymphatic system work with?
works with the immune system to protect the body from pathogens, toxins, and other invaders
What is immunity?
term that refers to a condition where the body is protected from various threats, like pathogens, toxins, and cancer cell
What are the 2 types of immunity?
innate and adaptive
What is innate immunity?
an immune response that does not require a previous exposure to the pathogen
What are the 4 types of mechanisms of innate immunity?
- physical and chemical barriers
- inflammatory response
- phagocytes and natural killer cells
- protective proteins
What lines the respiratory, digestive, and urinary tracts?
skin and the mucous membranes
Physical and Chemical Barriers
What does the skin and mucous membranes do as lining?
serve as mechanical barriers to entry of pathogens
Physical and Chemical Barriers
What is the upper respiratory tract lined with?
ciliated cells that sweep mucus and trapped particles up into the throat, where they can be swallowed or expelled
Physical and Chemical Barriers
What do the secretions of oil glands in the skin contain?
chemicals that weaken or kill certain bacteria on the skin
Physical and Chemical Barriers
What does the acid pH in the stomach do?
kills many types of bacteria or inhibits their growth
Physical and Chemical Barriers
What do various bacteria that normally reside in the intestine and other areas such as the vagina, do?
remove nutrients and block binding sites that potentially could be used by pathogens
Inflammatory Response
What is an inflammatory response?
a series of events initiated by damage to tissues, whether by physical trauma, chemical agents, or pathogens
Inflammatory Response
What does inflammation do?
tends to wall off infections and increase the exposure and access of the immune system to the inciting agent
Inflammatory Response
What are the 4 “cardinal” signs of an inflamed area?
- redness
- heat
- swelling
- pain
Inflammatory Response
What are most of the “cardinal” signs caused by?
capillary changes in the damaged area
Inflammatory Response
What are mast cells?
a type of immune cell found especially in the skin, lungs, and intestinal tract
Inflammatory Response
How do mast cells respond to damage?
by releasing histamine
Inflammatory Response
What is histamine?
a chemical that binds to receptors present on endothelial cells lining the blood vessels
Inflammatory Response
What happens when mast cells release histamine?
capillaries in the area dilate and become more permeable, allowing fluids to escape into the tissues, resulting in swelling
the swollen area may stimulate free nerve endings, causing the sensation of pain
the increased blood flow also causes the skin to redden and feel warm
Inflammatory Response
Which phagocytic cells play an important role in inflammation?
macrophages and dendritic cells
Inflammatory Response
What do macrophages and dendritic cells do when they are exposed to invading microbes?
they can release various proinflammatory cytokines
Inflammatory Response
What are cytokines?
chemical messengers that influence the activities of other immune cells
some cytokines secreted by macrophages and dendritic cells act on the brain to induce a fever response
Inflammatory Response
What do macrophages do after ingesting a bacterial pathogen?
release a cytokine called ‘tumour necrosis factor alpha’ (which acts on endothelial cells) and ‘interleukin-8’ (which attracts other types of immune cells to the scene
Inflammatory Response
What do the cytokines ‘colony-stimulating factors’ cause?
causes the bone marrow to produce more white cells
Inflammatory Response
What happens if the cause of inflammation cannot be eliminated?
the inflammatory reaction may persist and become harmful rather than helpful
Inflammatory Response
What anti-inflammatory medications can be used?
aspirin, ibuprofen, and cortisone can minimize the detrimental effects of chronic inflammation
Inflammatory Response
In what conditions can inflammation not be eliminated?
tuberculosis and some types of arthritis
Phagocytes and Natural Killer Cells
What are phagocytes?
“eating cells”
Phagocytes and Natural Killer Cells
What are usually the first white blood cells to enter an inflamed area from the blood?
neutrophils that may accumulate to form pus
Phagocytes and Natural Killer Cells
What happens when an inflammatory reaction continues after neutrophils enter?
monocytes will migrate from the blood to the tissues, where they are then called macrophages (“large eaters”)
Phagocytes and Natural Killer Cells
What happens when a neutrophil or a macrophage encounters a pathogen, especially a bacterial cell?
it will engulf (phagocytose) the pathogen into an endocytic vesicle, which fuses with a lysosome inside the cell
Phagocytes and Natural Killer Cells
What does the acid pH in lysosomes do?
activate hydrolytic enzymes and various reactive oxygen compounds, which can usually destroy the pathogen
Phagocytes and Natural Killer Cells
What are natural killer cells?
large, granular, lymphocyte-like cells that kill some virus-infected and cancer cells by cell-to-cell contact
Phagocytes and Natural Killer Cells
How do NK cells and cytotoxic T cells kill their target cells?
by inducing them to undergo apoptosis
Phagocytes and Natural Killer Cells
What do NK cells do that cytotoxic T cells don’t?
they seek out and kill cells that lack a particular type of “self” molecule, called MHC-I (major histocompatibility class I), on their surface
Phagocytes and Natural Killer Cells
Why are some virus-infected and cancer cells susceptible to being killed by NK cells?
these cells may lack MHC-I molecules
Phagocytes and Natural Killer Cells
Why are NK cells considered a part of the innate immune system?
- don’t recognize specific viral or tumours antigens
- don’t proliferate when exposed to a particular antigen
What is adaptive immunity?
an immune system that recognizes, responds to, and usually eliminates antigens from the body when innate defences have failed to prevent infection
What is an antigen?
any molecule that stimulates an adaptive immune response
How long does it usually take adaptive defences to fully activate?
5-7 days, and they last for many years
What does the adaptive immune system depend on?
primarily on the activity of B cells and T cells
What are B cells and T cells both capable of?
recognizing antigens because they have specific antigen receptors
What are antigen receptors?
plasma membrane proteins whose shape allows them to bind to particular antigens
Describe inflammatory response.
- due to capillary changes in a damaged area and the release of chemical mediators, such as histamine by mast cells, an inflamed area exhibits redness, heat, swelling, and pain
- reaction can be accompanied by other reactions to the injury
- macrophages and dendritic cells, present in the tissues, phagocytize pathogens, as do neutrophils, which squeeze through capillary walls from the blood
- macrophages and dendritic cells release cytokines, which stimulate the inflammatory and other immune reactions
- blood clot can form to seal a break in a blood vessel
Describe the diversification of B cells and T cells.
the maturation process allows for the creation of specific B cells and/or T cells for almost any possible antigen
Where and when are B cells usually activated?
in a lymph node or the spleen, when their receptors bind to specific antigens
What stimulates B cells to divide?
cytokines secreted by helper T cells
What are plasma cells?
most of the cells resulting from B cell division that are specialized for the secretion of antibodies
What are antibodies?
the secreted form of the receptor of the B cell that was activated
What are memory B cells?
type of B cell that are the means by which long-term immunity is possible
What happens when the same antigen enters the system again?
memory B cells quickly divide and give rise to more plasma cells capable of rapidly producing the correct type of antibody
What happens once an infection is cleared from the body?
new plasma cells cease to develop and most of the present undergo apoptosis
What is antibody-mediated immunity?
defence by B cells
What is antibody-mediated immunity also called and why?
humoral immunity
these antibodies are present in blood and lymph (historically, a humor is any fluid normally occurring in the body
What are antibodies also called?
immunoglobulins (Ig)
Describe the structure of an antibody.
- y-shaped molecules with two arms
- each arm has a “heavy” (long) polypeptide chain and a “light” (short) polypeptide chain
- these chains have CONSTANT regions, and VARIABLE regions
What is the constant region in the polypeptide chains of antibodies?
- sequence of amino acids is set
- the same within a particular type or class of antibodies
What is the variable region in the polypeptide chains of antibodies?
- sequence of amino acids varies between antibodies
- form the antigen-binding sites
What is the antigen-binding site?
the antigen combines with the antibody here in a lock-and-key manner
What is the outcome of the antigen-antibody reaction?
can have several outcomes, but often the reaction produces immune complexes of antigens combined with antibodies
What are immune complexes?
may mark antigens for destruction
How may antibodies “neutralize” viruses or toxins?
by preventing their binding to cells
What happens as a T cell leaves the thymus?
it has a unique T-cell receptor similar to the specific receptors on B cells
How are T cells different from B cells?
unlike B cells, there is no secreted form of the T-cell receptors, and T cells are unable to recognize an antigen without help
How are T cells able to recognize an antigen?
the antigen must be displayed to the receptors by an MHC (major histocompatibility complex) protein on the surface of another cell
What do helper T cells and cytotoxic T cells both have?
each type has a receptor that can recognize an antigen fragment in combination with an MHC molecule
How do helper T cells recognize antigens?
recognize antigens presented by specialized APCs (antigen-presenting cells) with MHC class II proteins on their surface
How do cytotoxic T cells recognize antigens?
recognize antigens presented by various cell types with MHC class I proteins on their surface
What is the difference between cytotoxic and helper T cells?
cytotoxic T cells often kill the cells they recognize
What is one method of killing used by cytotoxic T cells?
depends on storage vacuoles that contain many molecules of perforin and enzymes called granzymes
What does perforin do?
forms pores in the plasma membrane of the abnormal cell, which allows the granzymes to enter the target cell, inducing it to undergo apoptosis
the cytotoxic T cell is then capable of moving on to kill another target cell
When do cytotoxic T cells release perforin?
after an activated cytotoxic t cell binds to a virus-infected or cancer cell that is presenting foreign antigen on its MHC class I proteins
What are memory T cells?
type of T cell that may live for many years and can quickly jumpstart an immune response to an antigen previously present in the body
What is cell-mediated immunity?
immunity mediated by helper T cells and cytotoxic T cells
What does HIV/AIDS do to helper T cells?
- infects helper T cells and other cells of the immune system
- surpresses many components of acquired immune responses
- makes HIV-infected individuals susceptible to opportunistic infections
- infected macrophages and dendritic cells also serve as reservoirs for HIV
