Immune System Introduction Flashcards
What are the 3 physiologic functions of the immune system?
-prevent infections
-eradicate established infections
-protect against cancers
Immunity
resistance to infection
Immune system
collection of molecules, cells, and tissues that mediate resistance to infections
Immune response
coordinated response of the cells and molecules of the immune system to infectious and noninfectious foreign substances
Immunology
study of the immune system and its responses to infectious and noninfectious foreign substances
antigen
a foreign substance that may or may not induce an immune response
How big does an antigen need to be to induce an immune response?
100 kDa
immunogen
an antigen that always induces an immune response
-all immunogens are antigens, but not all antigens are immunogens
cytokine
proteins produced by many different cell types that mediate inflammatory and immune reactions
-mediate communication between cells of the immune system
chemokine
chemoattractive cytokines
-attract cells to sites of infection/inflammation
-play a vital role in cell migration from blood to tissues
-induce chemotaxis
chemotaxis
target cells moving from lower concentration to higher concentration due to a chemokine
-helps neutrophils move towards and phagocytize pathogens in an inflamed site of the body
complement
protein produced by macrophages and hepatocytes
-part of innate immunity
-kill pathogens by direct lysis by forming holes or their killing by phagocytes (such as macrophages and neutrophils)
pathogen
an organism that causes disease
-pathogens express many antigens
microorganism or microbe
organism that can be seen only through a microscope
extracellular pathogen/microbe
a pathogen or microbe that can live, grow, and multiply outside the host cell
intracellular pathogen/microbe
pathogen or microbe that lives and grows inside the host cell
-viruses
commensal bacteria
microorganisms living on or within another organism and derive benefit without harming the host
leukocyte
AKA WBC
-broad term for all types of immune system cells
-includes neutrophils, basophils, eosinophils, monocytes, dendritic cells, lymphocytes, and NK cells
Kupffer cells
fixed macrophages in the liver
histiocytes
macrophages found in normal connective tissue
microglia
macrophages found in brain
osteoclasts
macrophages found in bone
langerhans cells/dendritic cells
macrophages found in skin
lymphocyte
cells derived from lymphoid progenitor cells
-includes B cells, T cells, NK cells
What type of immunity are B cells?
humoral immunity
What type of immunity are T cells?
cell mediated immunity
What type of immunity are natural killer cells?
innate immunity
What are the primary cells of the adaptive immune system?
B and T cells
What are the two types T lymphocytes?
helper T lymphocytes (Th cells) and cytotoxic T lymphocytes (Tc cells)
Is a lymphocyte and type of leukocyte?
yes
How are different types of lymphocytes distinguished?
by expression of surface proteins that are named “CD molecules”
phagocytosis
cellular ingestion of large extracellular substances (such as macrophages engulfing whole bacterium)
opsonization
when proteins bind to an antigen to tag it for phagocytosis by phagocytes such as neutrophils or macrophages
What are the most common proteins to opsonize antigens?
antibodies and complement
extravasate
leakage of fluid out of a container
extravasation in the context of inflammation
WBCs (neutrophils particularly) leaking out of blood vessels in order to reach the site of tissue injury to remove injurious stimuli
What to venules contribute to to extravasation?
fluid, proteins, and majority of WBCs
What do capillaries contribute to extravasation?
mostly fluids and proteins and not many WBC
Naive T and B lymphocytes
not previously encountered their specific antigen and therefore have never responded to it
-all lymphocytes leaving the primary lymphoid organs
-differentiate when stimulated by antigens
Effector T and B lymphocytes
terminally differentiated from naive T and B cells
-responsible for performing effector functions to eliminate the pathogens or cancerous cells
Effector helper T cells
Th cells secrete cytokines to help other immune cells
effector cytotoxic T lymphocytes
CTLs, kill infected cells and cancerous cells
plasma cells
secrete antibodies
What is another name for effector B cells?
plasma cells
memory B or T cells
generated from differentiation of lymphocytes
-not considered effector cells
immunoglobulin
AKA antibody
Where are immunoglobulin (Igs) bound?
membrane bound on B cells or a soluble protein produced by the effector B cells (plasma cells)
What do Igs act as when membrane bound?
B cell receptor (BCR)
-interacts with antigen
What are Igs specific for?
particular epitope on an antigen
What do Igs do when soluble?
act to opsonize antigens
What do T cell receptors (TCR) do?
interact with a particular epitope on an antigen
What to TCR require to recognize an epitope?
epitope must be presented by major histocompatibility complex (MHC) molecules of an antigen presenting cell (APC)
What do APCs do?
internalize antigens and break them down into small pieces and then present them to T cells by their MHC molecules
What is a MHC?
major histocompatibility complex
What is the difference between how BCRs and TCRs recognize antigens?
BCR recognize antigens by directly binding to them and they do not require presentation of processed antigens by APCs
-B cells can bind to antigens in their native form, but T cells can not
What are the 3 types of APCs?
macrophages, dendritic cells and B cells
What to APCs present to?
T cells
What is the most efficient APC?
dendritic cells
epitope
alternative term for an antigenic determinant
-immunologically active discrete site on a macromolecular antigen to which an antibody or TCR (T cell receptor) actually binds
epitope in the case of a protein antigen recognized by a T cell
peptide portion that binds to an MHC molecule for recognition by the TCR
epitope in the case of B cells
a region of an antigen that antibody bind to with its antigen binding region
hypersensitivity
inappropriate immune responses such as autoimmune disease
-immune response against body’s own antigens or self-antigens
-hypersensitivity or allergic reactions
serum
yellow liquid that remains when blood clots and is then centrifuged to remove blood cells and clotting elements
Are clotting proteins and cells present in serum?
no
Are soluble proteins such as immunoglobulins and albumin present in serum?
yes
antiserum
serum containing antibodies against specific antigens
-antiserum against tetanus toxin has antibodies against the tetanus toxin
polyclonal antibody
a collection of antibodies from different B cells that recognize multiple epitopes of the same antigen
-antibody response generated following immunization or infection is a polyclonal antibody response
monoclonal antibody
antibody from a single antibody producing B cell
-only binds with one unique epitope
plasma
liquid portion of unclotted blood
-does not include any cells of the blood, but includes all soluble proteins found in serum
-also contains fibrinogen and other soluble clotting elements that are not found in serum
What is the oldest system of host defense?
innate immunity
-adaptive immunity evolved later
What species did adaptive immunity first appear in?
jawed vertebrates (sharks, rays, skates)
How long does it take for innate immunity to react vs adaptive immunity?
innate immunity: minutes to hours
adaptive immunity: days
What are the principal components of innate immunity?
-anatomical and chemical barriers (skin, mucous membrane, stomach acid, and complement proteins)
-effector cells
-inflammation
How long do neutrophils live?
short lived (few hours in blood, 1-4 days in tissue)
What is the major phagocytic cell of blood?
neutrophils
What does the nucleus of neutrophils look like?
multilobed
What is the main role of neutrophils?
killing extracellular pathogens
-bacteria or fungi
What do individuals with neutrophil defects suffer from?
recurrent chest infections with bacteria or fungi and recurrent skin abscesses
How long do macrophages live?
several months
What does the nucleus of a macrophage look like?
bean shaped single lobed nucleus
What do cytokines play a major role in?
initiating adaptive immune responses
What is the job of macrophages?
-phagocytosis and killing of extracellular pathogens
-secreting cytokines to make blood vessels leaky, attract other leukocytes, and lead to inflammation
-key role in removing debris or necrotic tissue and aged erythrocytes
Where do macrophages live?
in tissues of all organs
-have names depending on where they are located
Why are macrophages called antigen presenting cells (APCs)?
-capture pathogens or foreign antigens invading organs, lyse them, and present processed antigens to T cells
Macrophages are transformed cells of what cell?
monocytes: circulate for 8-70 hours and then migrate into tissues and become macrophages
Can macrophages and neutrophils kill intracellular pathogens?
no
