chap 7- acquiring immunity Flashcards
is the third line of defence specific and acquired
yes
what is the lymphatic system
a network of vessels, tissues and organs across the body that work together with the circulatory system and the immune system to fight infection
what are the main roles of the lymphatic system
return fluid to blood
filter tissue fluid
be a site of antigen recognition
transport leukocytes around body
be a site of lymphocyte maturation
what do lymph nodes do
filters lymph and traps foreign particles, cellular wastes, toxins and pathogens
what do the lymph nodes contain
lymphocytes (B and T cells), plasma cells, macrophages, dendritic cells and site where they encounter their antigens
what is the spleen
larger flattened organ located in upper left sector of abdomen
where are lymphocytes located
throat, armpits, abdomen and groin
how are lymph nodes sites for antigen recognition
as lymph moves through the lymph vessels, the lymph nodes filter and trap invading pathogens and foreign matter. when an antigen is present in a lymph node it can be recognised by leukocytes of the adaptive immune system (lymphocytes) become activated and initiate a response.
what does specific mean
specific to the pathogen presented
can third line of defense have memory
yes
what are the parts of the 3rd line of defense
lymphatic system, humoural response and cell mediated response.
what are B lymphocytes involved with
humoral immunity
what are T lymphocytes involved with
cell mediated immunity
what does cell mediated immunity target
intracellular pathogens, usually viruses that have broken through 1st and 2nd lines of defense and have gotten inside cells.
may also target self-cells that have turned cancerous
what are the types of T lymphocytes
helper T cells, cytotoxic T cells, memory T cells
what do helper T cells express once activated
MHC II markers
what do cytotoxic T cells do
initiate apoptosis in affected cells (similar to natural killer cells)
what do memory T cells do
contain “memory” of antigen and will differentiate into cytotoxic T-cells and proliferate if exposed to same antigen again
what are naive T lymphocytes
cells that havent yet encountered their specific antigen
what activates the cell mediated response
when a helper T cell encounters an antigen on an APC specifically to its antigen receptor
do T cells directly bind to antigen
no they bind to antigens presented on MHC markers
what are the steps in the cell mediated response
1- helper T cells bind on MHC II from APC
2- APC released cytokines which activate naive helper T cells which releases is own cytokines.
3- cytokines initiate proliferation/clonal expansion
4- cytotoxic T cells proliferae by dividing multiple times and forming an army of clones. some of these clones become effector ce;;s which are primed to destroy cells expressing the specific antigen that activated them
5- cytotoxic T effector cells release powerful cytotoxins directly into affected cells which work together to induce apoptosis in the target cell
6- other clones become memory cells which migrate in lymph nodes where they can be activated quickly if they come into contact with the same pathogen
what is clonal expansion
where multiple copies of T cell are produced and together release large amounts of cytokines designed to activate cytotoxic T cells
what happens if the same pathogen is encountered again after cell mediated immunity
Memory T cells that have migrated to lymph nodes are activated when they encounter the same pathogen and proliferate rapidly producing numerous copies of effector T cells.
This enables the pathogen to be fought off quicker
where does the humoral response occur
the humors of the cell bodily fluids including blood, lymph and interstitial fluid
what antigens does humoral response respond to
antigens on extracellular pathogens
what does humoral response result in
the production of antibodies in B lymphocytes
where do naive B cells form and mature
in the bone marrow and spleen
what are antibodies in the humoral response
B cell receptors on B lymphocytes
what are antibodies
quaternary proteins whih have a Y shape with 2 variable regions at the tips of the Y contain 2 identical binding sites that are complimentary to a specific antigen
when does clonal selection occur
if B cell encounters an antigen in the lymph nodes that specifically matches with its antigen receptor
what does the clonal selection theory propose
when B and T lymphocytes form, each has a receptor that is unique to them and that will react to a single antigen.
when will a lymphocyte differentiate and proliferate into a clone of millions of effector cells
once it has been activated by its specific antigen
what are the cloned effector cells dedicated to do
eliminate the specific antigen that stimulated the immune response
what occurs during humoral response
1- a B cell is triggered when it encounters its matching antigen
2- the B cell engulfs the antigen and digests it
3- then it displays antigen fragments bound to its unique MHC molecules
4- this combination of antigen and MHC attracts the help of a mature matching T cell.
5- cytokines secreted by the T cell help the B cell to multiply and mature into antibody producing plasma cells.
6- released into the blood, antibodies lock onto matching antigens. the antigen-antibody complexes are then cleared by the complement cascade or by the liver and spleen.
7- once antibodies have ben released from the plasma B cell they can lead to the destruction of pathogens in 4 ways, all of which can occur simultaneously
what is the alternative pathway
helper T cell with same receptor detects antigen displayed on MHC II marker of alternative APC.
Helper T cell releases cytokines which activate mature B cell with receptor specific to antigen
B cell undergoes clonal expansion and differentiation to produce plasma B cells and memory B cells
Plasma B cells release antibodies to locate and tag specific antigen
how long can plasma B cells live for
a few days and can secrete up to 10000 molecules of a specific antibody per second into circulation.
what is opsonisation
antibodies bind to antigens present on pathogen surface flagging them for destruction for phagocytes
what is aggulation
variable regions of antibody can bind to 2 different antigens causing them to clump together in an antibody pathogen net immobilizing them and preventing spread of infection and making them susceptible to phagocytosis.
what is cascade of complement proteins
antibodies that are bound to antigens can activate the cascade of complement proteins.
what is neutralization of toxins
antibodies can neutralize toxins of antigens by preventing them from binding to their target
how long can antibodies released by plasma B cells generally provide protection for
up to 28 days but the plasma cells tat secreted them can last for longer
how long can memory B cells survive for
years or even a lifetime.
if they encounter the same antigen again, they can initiate a rapid response through proliferation to produce plasma B cells
what immune systems do allergic reactions involve
both the innate and adaptive immune system
what is the process of becoming allergic
1- allergen is injested or inhaled. recognised as ‘non-self’
2- innate immune system is activated
3- adaptive immune system is activated. B cells produce IgE antibodies
4- IgE antibodies attach to mast cells. these mast cells are now primed. the person is now sensitised
5- second exposure to the alleren- mast cells are activated and release lots of histamine
6- inflammatory response- watery eyes, itchy nose etc
what is active immunity
results from the production of antibodies by the immune system in response to the presence of an antigen
takes time to develop, but the memory B and T lymphocytes ca provide immunological memory that can last a long time
what is passive immunity
results from the introduction of antibodies from another person or animal
immunity is immediae but cannot be maintained as the immune system in the recipient is not activated against the antigen
what is natural passive immunity
passive transfer of antibodies from mother to baby
what is artificial passive immunity
injecting antibodies into person. temporary protection
what is natural active immunity
get exposed to pathogen so person produces their own antibodies
what is artificial active immunity
vaccines make you produce your own antibodies
what is a live attenuated vaccine
involve a living microbe that has been weakened in the laboratory
e.g. chickenpox
what are inactivated vaccines
‘killed vaccines’ contain microbes that have been inactivated by heat, radiation or chemical means
e.g. influenza
what are subunit vaccines
contain part of pathogen whether that be the antigen itself or any molecule, such as proteins, peptides or polysaccharides
e.g. meningococcal
what are toxoid vaccines
use toxins that have beeb inactivated t stimulate an immune response
e.g. tetanus
what are messenger RNA (mRNA) vaccines
mRNA code triggers the body to make a protein unique to a virus, initiating an immune response
e.g. covid-19-pfizer
what is a primary immune response
bodys first injection of vaccination
what is secondary immune response
person after second injection of vaccination
what is herd immunity
when enough of a population is immunized that the people who cannot be immunized are safe from infection
