Immunology Flashcards
First stages of B-cell development (to immature B cell) (6)
Haematopoeisis Haematopoetic stem cell --> Common lymphoid progenitor --> Early pro-B cell --> Late pro-B cell --> Pre-B cell --> Immature B cell
Central tolerance of B/T cells?
Deletion of cells as they bind to SELF antigens
Virgin B cells express?
IgD and/or igM
How long do lymphocytes stay in bloodstream?
1 hour
% lymphocytes entering spleen after 1 hr?
45%
% lymphocytes entering lymph nodes
40%
How do lymphocytes leave the bloodstream into the lymph nodes?
Through high endothelial venules
B cells stay where in lymph node? How long?
Primary follicles within cortex - 12 hours
T cells where in the lymph node?
Paracortex
Why do B cells go through HEV?
Due to cytokines - CCL21 and CCL19
Why doe B cells go to cortex?
cytokines released by follicular dendritic cells - CXCL13
B cells survival in cortex?
Contact with FDCs and stimulation by BAFF (cytokine)
Ig H chain contains which gene segments?
V. D and J
Variable, diversity and joining
Ig L chain contains which gene segments
V and J
Variable and joining
Heavy chain gene rearrangement?
D to J recombination –> DJ
V to DJ recombination –> VDJ
Transcription
When does H chain rearrangement take place?
From Pro-B cell to pre-B cell
When does L chain rearrangement take place?
From pre-B cell to immature B cell
Secondary diversification aka affinity maturation?
Somatic hypermutation
- point mutations in variable region can increase/decrease affinity
Class Switching
- either just of constant chain…IgM to IgD for example
- OR switching of subclasses of constant chain
High affinity binding is tested on FDCs
Low affinity–> apoptosis
APCs?
Antigen presenting cells:
Dendritic cells
Macrophages
APC function?
Phagocytose, process and present antigen on MHC
T cell receptor recognise?
MHC (of APC) WITH foreign antigen bound
B cell receptor recognise?
Soluble antigen and presented antigen
T cell and MHC binding? (5)
- In lymph node…APC migrates there after binding peptide
- CD4+ cells bind to MHCII (helper)
- CD8+ cells bind to MHCI (cytotoxic)
- TcR has MHC and peptide binding sites
- Co-stimulating molecules produced by APC also activate (eg CD28)
CD8+ binding?
Causes proliferation of cytotoxic T cells
Bind cells presenting foreign peptide
Release cytotoxic granules…death to foreign cell
IL-2 causes?
Differentiation of T cells…clonal population of effector T cells
IL-12?
Causes Th1 cells
IL-4?
Th2 cells
Th1 cells? (3)
Cellular immune system
Maximises “killing efficiency” of macrophages
Causes proliferation of CD8 T cells (cytotoxic)
Th2 cells? (4)
Humoral immune response
B cell proliferation
Antibody class switching
Antibody production
B cell and T cell interaction?
B cell presents antigen on MHCII
Encounter Th cells (Th2) and paracortex/cortex boundary
MHCII+antigen bind TcR
B cell proliferates
B cells differentiation?
In apical light zone
Plasma cells:
- secrete antibodies (lots of RER), stay in lymph/spleen
- or in bone marrow - longer life
Memory cells:
- Express antibody on their surface
- In circulation
