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Unit 5: The Immune System (Chapter 23)
Terms in this set (108)
a complex series of physiological events that culminates in the destruction and elimination of foreign and abnormal substances
two basic types of immune response
nonspecific (innate) immunity - first, weaker defense
specific (adaptive) immunity - stronger defense that takes time to develop
three components of the immune system
1. physical barriers between internal and external environments - protection from pathogenic agents
2. leukocytes (white blood cells) - production of response
3. lymphoid tissues - where leukocytes develop, reside, and come into contact with foreign materials
The skin is made up of an outer _________ and an inner _______.
Describe the structure of the epidermis.
In general, tightly packed epithelial cells with no blood vessels.
Outermost layer = keratin and dead epithelial cells
Outer layer is shed continuously.
the protein that keeps water from entering the body through the skin
Describe the structure of the dermis.
Sebaceous glands secrete sebum into the hair follicle, lubricating hair and inhibiting bacterial growth.
acidic oily substance that inhibits bacterial growth in the hair follicle
neutrophils, eosinophils, basophils
three types of immune cells that mature in the tissues
macrophages, dendritic cells, and mast cells
Why do some white blood cells have cytoplasmic granules?
the granules contain secretory products that function in the development of the cells and removal of pathogens/particles.
neutrophils, eosinophils, monocytes, macrophages, and dendritic cells
____________ are the most abundant of the leukocytes and are particularly important in fighting bacterial infections.
Macrophages mature from ___________.
Why are lymphocytes unique?
have the ability to distinguish between self and nonself (specificity and memory)
three types of lymphocytes
B lymphocytes (B cells)
T lymphocytes (T cells)
What gives null cells their name?
they lack cell membrane components that are characteristic of B and T cells.
Most null cells are _________.
natural killer (NK) cells
foreign or abnormal molecules
What happens when B cells contact antigens?
They develop into plasma ells to secrete antibodies (immunoglobulins)
Antibodies are also called ____________.
What is the function of antibodies?
Antibodies mark specific antigens for destruction by other cells.
What happens when a T cell contacts target cells?
They develop into active cytotoxic T cells that destroy the cell.
How do T cells kill?
They secrete molecules that form pores in the cell's membrane which lead to the cell filling with fluid and bursting (lysis)
What cells are important for fighting viral infections? Why?
T cells and NK cells (NK cells can have immediate action since the T cell must transition to their cytotoxic form)
They kill cells not particles so they can fight the virus "from the inside".
Where are mast cells found?
in skin and mucous membranes
What do mast cells do?
What are the four types of dendritic cells?
Langerhans cells, interstitial dendritic cells, myeloid cells, lymphoid dendritic cells
What do dendritic cells do?
phagocytose/endocytose pathogens and activate certain types of T cells
___________ lymphoid tissues are the sites of lymphocyte production and maturation.
____________ lymphoid tissues are sites where lymphocytes generally contact pathogens or other foreign matter and become activated as part of the immune response.
Where are the central lymphoid tissues?
bone marrow, thymus, fetal liver
Where are the peripheral lymphoid tissues?
spleen, lymph nodes, tonsils, adenoids, appendix, lymph nodules (GI tract), Peyer's patches (GI tract)
What is the general structure common among the peripheral lymphoid tissues?
dense network of cells that trap microorganisms and foreign particles
four classes of pathogens
viruses, bacteria, fungi, parasites
ability of a specific pathogen to cause a disease
Why do people with HIV/AIDS have weakened immune systems?
the virus binds to CD4 receptors on helper T cells
two mechanisms by which bacteria cause diseases
invasion of tissue and release of toxins
What molecule facilitates the bacteria's adhesion to tissues?
adhesion which is found on the bacterium's outer surface
Exotoxins are primarily secreted by gram-________ bacteria.
Endotoxins are primarily secreted by gram-_________ bacteria.
three classes of exotoxins
cytotoxins, neurotoxins, enterotoxins
What do endotoxins do?
activate certain aspects of the immune system to induce fever and other symptoms of disease
two main classes of parasites
protozoans and metazoans
What distinguishes protozoans from metazoans?
Protozoans are unicellular, while metazoans are multicellular.
Which pathogens have no organelles?
viruses and bacteria
How do defenses distinguish between self and pathogens?
pathogen-associated molecular patterns (PAMPs)
How is nonspecific defense initiated?
proteins associated with nonspecific mechanisms act as pattern-recognition receptors that recognize and bind the PAMPs to initiate the proess
the body's nonspecific defenses include....
physical barriers, inflammation, interferons, the complement system
List the five major events that occur in inflammation.
1. nearby macrophages engulf debris and foreign matter,
2. nearby capillaries dilate and become more permeable to proteins and fluid,
3. foreign matter is contained,
4. additional leukocytes migrate into the region, and
5. recruited leukocytes continue to help clear the infection via phagocytosis
small proteins secreted by macrophages after attachment to pathogen
cytokines that act as chemical messengers between leukocytes
How is vasodilation and increased capillary permeability induced?
four characteristic symptoms of inflammation
redness (rubor), swelling (tumor), heat (color), and pain (dolor)
What substance suspends blood clotting long enough for leukocytes to flow to the injury site?
the anticoagulant heparin
Four events that characterize the process of signalling leukocyte movement through blood vessels
the adhesion molecules that allow margination to occur
selecting and then integrins
What attracts leukocytes to the site of injury?
chemotaxis through interleukin-8
four steps of phagocytosis
attachment, internalization, degradation, exocytosis
proteins that bind tightly to foreign material and make it easier for the phagocyte to engulf it
opsonins (includes antibodies)
Some cytokines (IL-1, IL-6, and TNF-α) stimulate liver cells to produce ___________, a group of proteins having a wide range of antibacterial and inflammatory effects.
What type of cell produces acute-phase proteins?
Give an example of an acute-phase protein.
particles produced by virus-infected cells that signal infection to surrounding cells, inducing cellular resistance.
What type of interferon is not secreted by virus-infected cells?
the type of protein that allows NK cells to form pores in infected/abnormal cell membranes
What is the ultimate product goal of the complement system's pathways?
to create the membrane attack complex (MAC) which inserts itself into the cell membrane and allows fluid to flow in
Describe the four mechanisms by which activated complement targets pathogens for destruction.
1. covalently bonding to pathogens and functioning as opsonins
2. recruiting more phagocytes to the site of infection
3. triggering histamine secretion by mast cells
4. development of an MAC
What are the three pathways for complement activation?
1. classical pathway - binding to antibodies that are already attached to bacterial cells
2. lectin pathway - binding of mannose-binding lectin to mannose-containing carbohydrates on bacteria or viruses
3. alternative pathway - binding directly to carbohydrates present on the surface of a broad range of bacterial cells
Which complement activation pathways are specific?
the classical pathway as it depends on the bodies antibodies
_ lymphocytes develop into ______ cells that secrete antibodies.
What is the immune system that is mediated by antibodies and other macromolecules? What type of lymphocytes yield this?
humoral immunity, B
What is the immune system that is mediated by cells that bind and kill abnormal cells? What type of lymphocytes yield this?
cell-mediated immunity, T
recognition sites on antigens
foreign or abnormal molecules on the surface of pathogens that can be detected by lymphocytes
How are B and T cells able to recognize antigens?
antigen-binding proteins (antigen receptors)
What distinguishes the five classes of antibodies?
five types of heavy chains
Describe the structure of the typical antibody.
Constant regions: two identical heavy chains + two identical light chains, joined by disulfide bridges.
Variable regions: antigen-binding sites
Antigen receptors on T cells are called ___________ and (are/are not) secreted.
T cell receptors (TCRs), are not
Antigen receptors on B cells are called ___________ and (are/are not) secreted.
membrane antibodies/immunoglobulins, are
The antigen-driven activation of lymphocytes is called ____________.
What are the two populations of cells that are generated from B lymphocytes?
effector cells and memory cells
Which lymphocyte clone cell is short-lived and combats the same antigen that stimulated their production?
Which lymphocyte clone cell is long-lived and bears membrane receptors specific for the same antigen that stimulated their production?
The ____________ immune response occurs when a person is first exposed to an antigen.
The _____________ immune response occurs when there are subsequent exposures to an antigen.
_____________ immunity = secondary immune response
How do lymphocytes generate self-tolerance?
in the bone marrow and thymus, the receptors are tested for their potential to recognize and react against self. If they react against self, they undergo apoptosis.
What are the antigens that evoke the production of both plasma and memory B cells?
What is a helper T cell's role in B cell proliferation?
It secretes cytokines (including IL-2) which along with T-dependent antigens, induce proliferation.
What type of macromolecule are T-independent antigens?
State the five ways in which antibodies help eliminate antigen.
4. Complement Activation
5. Enhanced Activation of NK cells
In _____________, the antibody blocks an antigen's activity just by binding to it
In ___________, multiple pathogens are aggregated by antibody molecules.
All classes of Ig can mediate the simplest forms of antigen attack which are....
agglutination and neutralization
In ___________, pathogens bound to antibodies are more efficiently engulfed by phagocytes.
In ___________, antibodies bind to pathogens which activates the complement cascade and results in lysis (MAC).
In ___________, abnormal body cells bound by antibodies are recognized by NK cells and are subsequently lysed.
enhanced NK cell activity
____________ T cells produce cytokines that suppress the activity of B cells, helper T cells, and cytotoxic T cells.
What is the difference between T and B cells in the way they detect antigens?
For T cells to be activated, their antigen receptors must contact an major histocompatibility complex (MHC) molecule on the surface of some other body cell that is bound to a small fragment of antigen.
Class __ MHC molecules are found in phagocytes, which take foreign antigens into the cell through phagocytosis or receptor mediated endocytosis.
Helper T cells are also called ___ cells because of this surface protein that binds to Class II MHC.
_________ are proteins released by cytotoxic T cells that first gain entry into target cells through the perforin-induced pores and then work their way inside the cells to bring about death through apoptosis.
Name five cytokines secreted by activated helper T cells.
IL-2, IL-4, IL-5, IL-10, interferon-γ
_______ immunity is protection conferred when ready-made antibodies are introduced into the body.
__________ immunity is conferred when infection produces an immune response as protection.
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