The Immune System Flashcards
What is innate immunity?
aka “nonspecific immunity”; composed of defenses that are always active against infection but lack the ability to target specific invaders
What is adaptive immunity?
aka “specific immunity”; the defenses that target a specific pathogen; slower to act but maintains an immunological memory of the an infection to mount a faster attack in subsequent infections
What does bone marrow do?
produces leukocytes
What does the spleen do?
location of blood storage and activation of B cells
What is humoral immunity?
A division of adaptive immunity in which the antibodies dissolve and act in the blood instead of the cell
Where is the thymus?
in front of the pericardium, the sac that protects the heart
What do B-cells do?
turn into plasma cells to produce antibodies as part of adaptive immunity
What do T-cells do?
coordinate the immune system and directly kill virally infected cells
What do lymph nodes do?
provides a place for immune cells to communicate and mount an attack; B cells can be activated as well
What are the gut-associated lymphoid tissue (GALT)?
tonsils, adenoids, Peyer’s patches in the small intestine, and lymphoid aggregates in the appendix
What are the organs associated with the immune system?
(1) Lymph nodes
(2) Bone marrow
(3) Thymus
(4) Spleen
Hematopoietic stem cells give rise to _______, ________, ______ and _______.
granulocytes; agranulocytes; red blood cells; platelets
What are the three types of granulocytes?
neutrophils, eosinophils, basophils
What are two types of agranulocytes?
lymphocytes and monocytes
Monocytes become ____ when they move from blood to tissue.
macrophages
What are macrophages called in the CNS?
microglia
What are macrophages called in the skin?
Langerhans cells
What are macrophages called in the bone?
osteoclasts
What are the two categories of specific immunity?
Humoral - driven by B cells and antibodies
Cell-mediated - driven by T cells
What are defensins?
antibacterial enzymes found on the skin
What is lysozyme?
a nonspecific bacteria enzyme secreted in tears and saliva
How does the GI tract contribute to the immune system?
(1) Acid eliminates a lot of bacteria
(2) Large gut bacteria population keeps competitors at bay
What is the complement system?
many proteins in the blood that act as a nonspecific defense; they punch holes in the walls of the bacteria, making them osmotically unstable
Classical vs alternative pathway
Classical requires binding of an antibody to a pathogen to activate the complement system and alternative does not
Interferons
proteins that prevent viral replication and dispersion by causing nearby cells to decrease production of viral and cellular proteins and decreases permeability of the cells; upregulate MHC I and II molecules
What are the four main functions of macrophages?
(1) Phagocytizes the invader through endocytosis
(2) Digests using enzymes
(3) Presents peptide pieces of the invader to other cells using MHC
(4) Release cytokines
What is major histocompatibility complex?
MHC binds to a pathogenic peptide and carries it to the cell surface where it was recognized by cells in the adaptive immune system
What are cytokines?
chemical substances that stimulate inflammation and recruit additional immune cells to the area
What kind of cells have MHC-I molecules?
all nucleated cells display this
What kind of cells have MHC-II molecules?
only displayed by professional antigen-presenting cells like macrophages
What is endogenous pathway?
MHC-I pathway; binds pathogens that come from inside the cell
What is an antigen?
a substance that is targeted by an antibody
What is exogenous pathway?
MHC-II pathway; when antigens are from outside the cell and eaten by macrophages and presented on MHC-II
Name four profession antigen-presenting cells
macrophages, dendritic cells, some B cells and come epithelial cells
What are pattern recognition receptors (PRR)?
special receptors on macrophages and dendritic cells that recognize the type of invader so the cell can release appropriate cytokine
What is a common PRR?
toll-like receptors (TLR)
What are natural killer (NK) cells?
a type of nonspecific lymphocyte are able to detect the downregulation of MHC and induce apoptosis in these virally infected cells
What are neutrophils?
most populous leukocyte in blood and very short-lived; follow bacteria using chemotaxis and phagocytosis the bacteria; can detect once they have been opsonized and attack
What is opsonized?
when a bacteria has been marked with an antibody from a B-cell
What causes pus?
dead neutrophil collections
What are eosinophils?
contain bright red-orange granules and primarily involved in allergic reactions and invasive parasitic infections; release histamine upon attack
What effect does histamine have?
results in vasodilation and increased leakiness of the blood vessels, allowing additional immune cells to move out of the bloodstream and into the tissue
What are basophils?
contain large purple granules and are involved in allergic responses; least populous leukocytes
What are mast cells?
closely related to basophils, but have smaller granules and exist in the tissues, mucosa and epithelium
What is another name for antibodies?
immunoglobulins (Ig)
What are the three possibilities for antibodies are secreted into body fluids?
(1) Once bound to a specific antigen, antibodies may attract other leukocytes to phagocytize those antigens immediately
(2) Antibodies may cause pathogens to clump together and form insoluble complexes that can be phagocytized
(3) Antibodies can block the ability of a pathogen to invade tissues, neutralizing it
What happens when an antigen binds to cell surface antibodies of a B-cell?
causes activation of that cell, resulting in its proliferation and formation of plasma and memory cells
What happens when an antigen binds to the cell surface antibodies of a mast cell?
causes degranulation, or exocytosis of granules contents, releasing histamine and causing an inflammatory allergic reaction
What is the clumping of particles together called?
agglutinate
What is clonal selection?
B-cells that can bind the antigen with high affinity survive, providing a mechanism for specificity
What are the five types of antibodies?
IgM, IgD, IgG, IgE, IgA
What is isotype switching?
cells can change which isotype of antibody they produce when stimulated by specific cytokines
What is the structure of an antibody?
Y shaped, two heavy chains on inside of the tips and light chains on the outsides, the whole tip is considered a variable region where antigen’s bind, the constant domain (the bottom part) is where cells have receptors that bind to it
When exposed to antibodies what do B cells do?
B cells will produce plasma cells (which produce antibodies) or memory B cells which stay in lymph nodes and remember the pathogen for life.
What is the primary response?
take 7 to 10 days; B-cells producing plasma cell and memory B cells for the first time the pathogen is encountered
What is the secondary response?
when a pathogen that the body has encountered before is back, memory B cells produce antibodies specifically for that and this response is faster and more robust
What is positive selection?
only allowing the maturation of T-cells that can respond to the presentation of antigen of MHC
What is negative selection?
causing apoptosis in T-cells that are self-reactive to prevent autoimmunity (activated by proteins produced by the organism itself)
What is thymosin?
a peptide hormone secreted by thymic cells that facilitate the maturation of T cells
What are helper T-cells (Th)?
CD4+ T-cells; respond to antigen presented on MHC-II molecules that coordinate immune response by secreted lymphokines. This allows them to recruit other immune cells and ramp up activity; without them their would be a loss of adequate response;
What are cytotoxic T-cells?
CD8+ T-cells; capable of directly killing virally infected by injecting toxic chemicals that promote apoptosis into the infected cell; respond to antigens presented on MHC-I molecules
What are suppressor T cells?
regulatory T-cells (Treg) - express CD4 and Foxp3 and help tone down the immune response once infection is contained; turn off self-reactive lymphocytes
What is self tolerance?
turning off self-reactive lymphocytes to prevent autoimmune diseases
What are memory T cells?
cells lie in wait until exposure to the same antigen and then carry out a faster more robust response
What are self-antigens?
the proteins and carbohydrate present on the surface of every cell of the body
What is autoimmunity?
when the immune system fails to recognize self from foreign and attacks its own cells
What is active immunity?
the immune system is stimulated to produce antibodies against a specific pathogen
What is passive immunity?
results from the transfer of antibodies to an individual
What are lymph nodes?
small, bean shaped structures in the lymphatic vessels that contain a lymphatic channel, artery and vein. They provide a space for the cells of the immune system to be exposed to possible pathogens
What is chyle?
lymphatic fluid carrying many chylomicrons with a milky white color
What are lacteals?
small lymphatic vessels located at the center of each villus in the small intestine
What are germinal centers?
B-cells that proliferate and mature in the lymph nodes in collections
