Immunology Flashcards
(41 cards)
What are the 2 primary lymphoid organs
bone marrow
thymus
what does the bone marrow do
produces haematopoeitic stem cells- T cells, B cells, NK cells
RBCs are produced by these stem cells
what happens in the thymus
positive and negative selection of T cells
so maturation of T cells occurs here
what happens to the thymus as you get older and what problem does this cause in elderly
it dissolves
the elderly therefore can’t produce antibodies to fight infection as easily because T cells can’t mature quickly
what are the secondary lymphoid organs
lymph node
spleen
what is the spleen and it’s function in immunological response
it’s an organ found top L of abdomen
its role is to filter blood but it is also involved in the immune response
a lot of blood passes through the spleen- captures antigens in blood
what 2 things is the spleen composed of
red pulp- has red blood cells
white pulp- has immune cells- T and B cells
white pulp in the middle surrounded by red pulp and then immune response kicks in either CD4- B cells- antibodies or CD8- apoptosis
Lymph nodes
collects antigens from tissues
an area where B and T cells can talk to each other
where does the positive and negative selection process occur
in the thymus (lymphoid organ)
characteristics of starting cell that enters the thymus for positive and negative selection process
it is naive, undifferentiated
double +ve ie CD8 and CD4
what is the first stage of positive and negative selection
this is the positive selection part
so after the naive cell enters the thymus it encounters MHC1 and MHC11 receptors on B cells and interacts with the self antigen on them
those that interact with appropriate affinity (ie those that don’t react move on as shouldn’t have high affinity for SELF don’t want to kill it)
those that don’t APOPTOSIS
What is the second stage of positive and negative selection
now the negative selection part…
the cells that passed positive selection are then shown self-antigen on antigen presenting cells
this is the T cell receptor and MHC1 or MHCII (t and b cell speaking)
if the interaction is too strong the cells die (apoptosis- happens to most cells)
what happens to leftover cells after positive and negative selection
the leftover cells won’t have reacted to any self-antigens and therefore NORMAL
can enter the systemic circulation
they lose either one of their CD4 or CD8 expression so differentiate before they leave the thymus
Natural killer cells
2 types - pure innate and innate/adaptive
NK cells detect foreign antigens
they don’t engulf the stricken cell but instead attach to it and release PERFORIN and GRANZYME into the cell and induce apoptosis
you can’t educate it/make it better over time
the innate/adaptive express a T cell receptor on the NK cell so are said to be partly adaptive
what is the complement fixation test
a test for infection with a microorganism
detect the presence of either specific antibody or specific antigen in a patient’s serum,
missing self hypothesis
every cell in our bodies expresses MHCI receptor on their surface
viruses can remove these MHC1 receptors however
so NK cells roam through the body looking out for these receptors to know that the cell is ‘self’ and normal
if it can’t see the MHC1 (virus took it away) then it becomes activated and releases perforin and granzyme- apoptosis
they help with tumour surveillance by killing cancerous cells
difference between apoptosis and cell lysis
lysing a virus-infected cell would only release the virions (splits the cell and kills it but releases contents
whereas apoptosis leads to destruction of the virus inside.
what do Natural killer cells try to contain
they try to contain viral infections while the adaptive immune response is generating antigen-specific cytotoxic T cells that can clear the infection.
describe the innate response
- present at birth
- 1st line of defence (if physical barriers fail)
- no immunological memory created, no education- can’t get better over time
- occurs in the same way at the same speed every time
- may completely eliminate the agent before the specific adaptive immune response is called upon
- also interacts with the adaptive immune response, aiding its activation and modulating the response.
what are the key cells involved in innate immunity
phagocytes- dendritic cells (in the tissues/lymphoid tissues)
macrophages- phagocytes- key to activating adaptive
complementary proteins (the complement system) - link between innate and adpative
inflammatory mediators (chemicals like histamine)
white blood cells like neutrophils, eisonophils, basophils, mast cells, NK cells
what 4 WBCs involved in innate response are granulocytes
neutrophils- arrive first at site of infection- contain granules and are also phagocytic
basophils- contain cytotoxic granules
eisonophils- phagocytic
mast cells- histamine
which cells from the innate system are responsible for speaking to the adaptive system and activating it and how do they do this
macrophages or dendritic phagocytic cells
they present the antigen of the pathogen to the T cells in adaptive immunity
they are called antigen presenting cells
can present to both types of T cells
however tend to present antigens originating inside the cell to cytotoxic T cells so apoptosis can be induced and it can kill virus inside cell
and antigens on surface are presented to T helper cells that go on to activate B cells (antibody production), NK T cells and macrophages
why is the adaptive system brought in after innate
the innate phagocytes will try to consume and destroy the pathogen but if it can’t they will recruit help and activate adaptive system (can take weeks however) and in the meantime innate will try to contain infection
what are the 2 types of T helper cells and what are their functions
Th1 and Th2 (converted into B cell)
present the antibody to a B-cell which then produces antibodies
