anatomy and surveillance Flashcards
what T cells are removed during clonal deletion ?
the ones that bind too tightly to self MHC peptide complex
the large number of lymphocytes that are produced from a single progenitor , do they all have the same specificity?
no they all have a different specificity
how does the T cell precursor produce diversity and where does this occur ?
in the thymus it rearranges it’s T cell genes through somatic recombination.The TCR are diverse
what happens in the thymus if the immature T cell recognises self MHC and binds moderately ?
it receives a signal for survival
what happens to the T cells that interact with self antigens ?
they are removed by apoptosis
what happens to the mature T cell after selection has occured ?
move to the periphery lymphoid organs from the thymus and it is here that they encounter foreign antigens and become activated and matured fully.
what happens once the T cells become activated ?
they acquire effector functions. The activated T cells then proliferate and migrate to the site of infection to eliminate it.
name the primary lymphoid organs ?
thymus and bone marrow
what are lymph nodes ?
small glands that filter lymph that circulates the lymphatic system.
what are the lymph nodes ideal for ?
ideal environment for communication of immune cells
where do the lymphocytes encounter and respond to antigens ?
in the peripheral lymphoid organs
what is the Peyers patch ?
this is the lymphoid organ that is near the intestine
what is situated in the inner paracortical area ?
this is where the T cell are
what is situated in the outer area called primary lymphoid organ ?
this is where the B cells are
do the B and T cells have seperate areas or are they in the same section ?
separate areas
what occurs in the germinal centre ?
the B and T cells meet and they can activate each other
what does the naive T cells do ?
migrate through the secondary lymphoid tissues
what does the dendritic cells act as in the lymphoid organ ?
act as APC in the T cell area of the lymph node so that they can initially activate the naive T cell.
what happens if the naive T cell does not become activated by the dendritic APC in the lymph node ?
it exits the lymph node via the cortical sinuses
how do naive lymphocytes enter the lymph nodes ?
via the blood
how are peptides presented to the TCR in context of the MHC ?
in two forms
– MHC-I - CD8+ T cells – killer cells
– MHC-II - CD4+ T cells – helper T cell
how is the adaptive immune response initiated?
by the antigen and antigen presenting cells in the secondary lymphoid organs.
what occurs if the T cell recognises the antigen/MHC ?
T cell and APC have an interaction and the TCR transmits a signal and the T cell becomes activated
what happens once the T cell becomes active ?
proliferates it can no longer exit the lymph node and it is here that it differentiates into the effector cell of either Cd4+ or Cd8+ and then exits the lymph node.
what do cytokines do in the role of adaptive immune ?
they influence the effector functions
how are most pathogens kept outside the body ?
by the epidermis layer which acts as a barrier
when will the pathogen enter the dermis layer by crossing the epidermis layer ?
when there’s been a breach to the barrier for example an injury.
what do T cells in turn activate ?
B cells and this results in production of antibody after plasma cell has been differentiated.
give example of how CD4+ cells are helpers ?
activate macrophages to become more cytotoxic while the antibodies recruit complement to lyse the pathogen directly by causing opsonisation so that phagocytes can be recruited to kill them.
what is activated first to try and control the infection ?
the innate immune systems
what happens if the innate cannot control the infection ?
the threshold is reached and the adaptive is induced. This is called the inductive phase
what happens after the inductive phase ?
T cells are activated the effector phase occurs in the peripheral where the Cd4+ and Cd8+ are induced.
what occurs when someone has been vaccinated ?
time of the effector phase has been shortened and the threshold is lower.
