b cells activation Flashcards
1
Q
what do b cells do
A
- receptors which recognise antigens
- recognise pathogens through toll like receptors
- release antibodies
- present phagocytosed antigen on MHCII
2
Q
how do T cells activate b cells
A
- in the presence of T cells which have been activated and recognise the antigen presented by the b cell
- the t helper cell release cytokines
- the b cell matures into a plasma cell and starts to produce specific antibodies
3
Q
what are the antibody classes
A
- Igd - b cell receptor
- IgM
4
Q
what are the specialised antibodies
A
- IgG
- IgE
- IgA
5
Q
t follicular helper cells
A
- t helper cells become activated and leave the lymph node to go to the tissue
- after activation by a dendritice cell some T helper cells upregulate Bcl-6 and become follicular helper cells
- after initial interaction some B and T cells will migrate to the medullary cords and proliferate (produce IgM)
6
Q
stages of what occurs in the germinal centre
A
- b cells move away from the t cell border and starts to proliferate - undergo somatic hypermutation
- b cells interact with antigen presented on follicular dendritic cells and also continue to interact with tFH receptors receiving CD40L - CD40 signals to survive and continue proliferation
- if they recognise the antigen with high affinity the mature onto plasma cells and leave the germinal centre
- some of the cell cells will become memory be cells
- if the b cell has a low affinity for the antigen or is self-reactive it undergoes apoptosis and is removed by the tangible body macrophages
7
Q
what is somatic hyper mutation
A
mutations occurring in the variable region of the b cell receptors
8
Q
what is class switching
A
changing the constant region
9
Q
what are the different ways for complement activation to occur
A
- opsonisation
- sensitising for killing by NK cells
- neutralisation
- sensitising mast cells and activating eosinophils
10
Q
stages of of complement activation
A
- antibodies at site of infection recognise th antigen on the surface of the pathogen and bind
- recruits complement protein C1 activating classic pathway of complement activation
- results in C3b becoming bound to the surface pathogen
- phagocytes recognise the bound C3b through complement receptors initiating phagocytosis
11
Q
opsonisation
A
- IgG
- antibodies recognise antigen of pathogen surface
- phagocyte recognises bound antigen through Fc receptor initiating phagocytosis
12
Q
sensitising for killing by NK cells
A
- antibodies originally produced against the virus bind to same proteins on surface of cells
- NK recognise Fc receptors and kill the cells
13
Q
neutralisation
A
- IgM, IgA, IgG
1. virus gains entry to cell binding to surface receptors
2. bacterial toxins can bind cell receptors can cause damage/ death to cell
3. antibodies bind to bacterial toxins/ virus particles to stop them reaching their receptors on the cells and prevent infection/ damage
14
Q
sensitising mast cells by activating eosinophils
A
- IgE - recognised by FceR1
1. IgE binds to surface of parasite. bound IgE is recognised by FceR1 on eosinophils
2. eosinophils release their granule contents to degrade parasite
3. IgE can become bound to FceR1 on mast cell
4. when antigen binds the antibodies this causes cross linking and the mast cell degranulates releasing contents (histamine, leukotrienes)
15
Q
what are the 2 ways of t cell independent b cell activation
A
- mature plasma cells reside in some barrier tissues of the body producing antibodies
- specialised B cells in the peripheral tissues can be activated independently of T cell by dendritic cells
