T Cells & Acquired Immunity Flashcards
What is a cytotoxic T cells
It is a killer cell that destroys target cells that bear nonself antigens and it kills the whole cell
What is a helper T-cell
It secretes hormones known as cytokines that bind on B cells
What is a suppressor T-cell
It’s secrete hormones that bind to receptors on other immune cells to terminate their activity
What is a memory T-cell
It is in a semi dormant state but rapidly reactivated on a second exposure to the antigen they are specific for, it is part of the secondary immune response
Classes of T cells
Cytotoxic, helper, suppressor, memory
Cytotoxic T cells respond to antigen is presented in
MHC class one context- the CTL will only kill the target once the engagements are complete
Helper T cells respond to antigen presented in
MHC class two context- It double checks the identity of presenting cell before it becomes activated to secrete molecular messages that promote further immune response
What are the two pathways
Endogenous which is inside the cell and exogenous which is outside the cell
T-cell receptor rearrangement have
An alpha and beta subunit
MHC class one characteristics
Found on all nucleated cells
Presents antigen directly to CD8+ cytotoxic T cells
Presents peptide fragments derived from intracellular antigen
Peptide fragment is loaded onto MHC class one in the rough ER
MHC class two characteristics
Found only on antigen-presenting cells e.g. B-cell, macrophage, dendritic cell
Presents antigen to CD4+ helper T-cell
Presents peptide fragments derived from extracellular antigen
Peptide fragment is loaded onto MHC class two in endosomal vesicles
CD4+ T cells characteristics
Recognise antigen presented in MHC class II context by professional APCS
On activation they secrete a variety of chemical messengers that stimulate immune response
T-cell receptor typically responds to antigen is derived from the exogenous pathway
Require stimulation by an APC before full activation occurs
CD8+ T cells characteristics
Recognise antigen presented in MHC class I context on infected body cells
On activation they engage with an attack target cells by triggering apoptosis and damaging the cell membrane
T-cell receptor response to antigens derived from the endogenous pathway
Requires stimulation by infected target cell and a CD4+ helper T-cell before full activation occurs
B-cell characteristics
Develop and partially mature in the bone marrow
Recognise intact protein antigen -soluble a pathogen associated
Receptor is both on the cell surface and secreted
Subsets are reported but no major differences
Mutate the receptor during affinity maturation
T-cell characteristics
Originate in the bone marrow but develop further in the thymus
Recognise peptides arrived from processed antigen and presented to them by another cell
Receptor is on the cell surface only
Major subset differentiation (CD4+ and CD8+)
No affinity maturation takes place
