B3 T and B cell function Flashcards
T and B cell function
adaptive immune responses are initiated by
adaptive immune responses are initiated by antigen and antigen-presenting cells in secondary lymphoid tissues
dendritic cells in secondary lymphoid tissues
-immature dendritic cell reside in peripheral tissue
-dendritic cells migrate via lymphatic vessels to regional lymph nodes
-mature dendritic cells activate naive t cells in lymphoid organs such as lymph nodes
how are CD4 and CD8 effective in responding to antigens
they have cell surface proteins which make direct contact to MHC mols
proliferation T cell function
-huge diversity meaning antigen specific t cells are rare
-activated t cells are useful so need to proliferate to generate effective immune response
T cell effector functions
CD4 T cells helper
CD8 T cells killer
Polarisation of CD4 T cell response
Th1- secretes IFNy and activates macrophage functions
Th2- secretes IL-4 and helps antibody function
Memory T cell function
-key feature of adaptive immune system
-vaccines
-distinct from innate immune system
the 4 T cell functions
-proliferation
-effect functions
-polarisation of CD4 T cell response
-memory
how does CD8 carry out effector function
-stimulation of naive t cell
(recogniton)
-proliferating t cell
(proliferation/differentiation)
-active effect t cells kill virus infected target cells
(effector function)
how does CD4 carry out effector function
CD4 cells carry out their effector function by helping b cells make antibodies
-antigen recognition induces expression of effector molecules by the T cell, which activates the B cell
-B cell proliferation
-differentiation to resting memory cells and antibody secreting plasma cells
what 3 kinds of signals do antigen-presenting cells deliver to naive t cells
- activation
- survival
- differentiation
stages of B cell activation
- recognition of antigen by BCR leads to activation of B cell and internalisation of antigen
- once internalised antigen is broken down into peptides
- peptides are loaded into MHC II within B cell and presented to antigen specific CD4 T cells
- If T cell also recognises antigen provides help to B cell (cytokines, costim)
- allows B cell to fully activate and secrete antibodies
what are B cells highly efficient at
presenting antigens that bind to their surface immunoglobin
how do B cells provide help
CD4 helper t cells provide help to b cells via CD40
T cells influence antibody production through secretion of cytokine
induces proliferation of B cell and differentiation
-plasma cell (antibody secreting
-memory cell
what do Tfh cells provide
viral specific Tfh cell provides help to B cells that recognise a linked epitope
antibody summary
known as immunoglobulin (Ig0
multi unit protein
-heavy chain
-light chain
-disulphide bonds to link
2 regions
-variable region
-constant region
antibody summary
known as immunoglobulin (Ig0
multi unit protein
-heavy chain
-light chain
-disulphide bonds to link
2 regions
-variable region
-constant region
what is the binding site of an antibody
epitope
(can be linear sequence or based based on antigen folding
what does the hinge region of Ig mols do
allows flexibility in binding to multiple antigens (60 or 90 deg)
what can high affinity IgG and IgA do
neutralise toxins and block infectivity of viruses and bacteria
what pathway do antibody:antigen complexes activate by binding to what
classical pathway
binding to C1q
what receptors on phagocytes are activated by antibodies
Fc receptors
what do Fc recep on phagocytes that are activated by antibodies bound to the surface on pathogens do
enable the phagocytes to ingest and destroy pathogens
stages of phagocytosis and IgG
- bacterium coated with complement and IgG antibody
- when C3b binds to CR1 and antibody binds to Fc recep, bacteria are phagocytosed
- macrophage membranes fuse, creating phagosome
- lysosome fuse with vesicles, delivering enzymes that degrade the bacterium
antibody isotypes
isotype of an antibody related to constant region expressed by B cell
different isotypes of antibody mediate different functions and associated with different locations
what is associated with cytokines produced by CD4 helper T cells
isotype of antibody secreted by B cell (plasma cell)
what cell expresses FceR1 which only binds with what Ig and the result of this
mast cells
when IgE binds to antigen it cross links FcR1 receptors and this results in degranulatin of mast cells
= anaphylaxis
what cell expresses FcyR which only binds with what Ig and the result of this
macrophages
when IgG binds to ntigen on pathogen, FcyR receptors cross link and activates macrophage to engulf and destroy pathogen
function and location of IgG
found in blood and extracellular fluid
neutralise toxins, viruses, and bacteria, opsonise them for phagocytosis and activate the complement system
function and location of IgM
found in blood and lymph
present on B cells and function is to control B cell activation
function and location of IgA
most abundant, mucous membranes (gut)
protects mucosal tissues from microbial invasion and maintain immune homeostatsis
function and location of IgD
functions as a B cell antigen receptor
found on B lymphocytes
does not bind complement
function and location of IgE
role in pathogenesis of allergies
found in lymphnodes draining site of antigen entry
