How long does the adaptive system responce last for
Days - Weeks
Does does the adaptive immune responce carry out recognition
Via antigen : antigen receptros
Where are B and T cell produced
Bone marrow
- B cells mature in bone marrow
- T cells mature in the thymus
What are the 2 types of T-cells
-
CD4+ T cells - regulate immune system
-
CD8+ T cells - kill virally infected cell bodies
That is the difference between PAMPS and Antigens
- PAMPs
- Non specific recognition
- Limmited number of PAMPS that are common to many different pathogens
2. Antigens
- Specific recognition
- Millions of different ones that are unique to individual species
- Individual B and T cells express ony one specific receptor for an antigen
What is the B cell antigen receptor - BCR
Memebrane bound antibody - IgG/IgD
Explain the T cell antigen receptor
Membrane bound alpha,Beta Heterodiamer
- Alpha chain
- Beta chain
Describe antibodies
- Produced by B-cell in responce to an antigen
- Bind specifically to that antigen
- Are expressed on surface of B cells and also secreted by B cells as soluble protiens
- Provide defence againts ectracellular pathogens - Bacteria, viruses and toxins
Desctibe the structure of antibodies
-
2 Ig heavy chain and 2 Ig light chain polypeptides held together by disulphide bonds
- Each Ig heavy chain and light chain contains:
- Variable region
- Constant domaine
Why can antibodies have different reachs
Flexible at hinge
How can different antibodies exist if they have the same structure
Have different Ig heavy chain regions
What are the different types of heavy chains and antibodies
Which part of the antibody is the antigen binding site
Hypervariable regions of Ig light and heavy chains combine to form antigen binding sites
Describe the TCR and its binding site for antigens
- Membrane bound heterodimer of alpha and beta chains
How can the immune cell recognise millions of different antigens
- B cells -•Antibody heavy and light chain proteins are encoded for by segmented genes in the germ-line genome of haematopoietic stem cells
-
Randome rearrangment in these gene segments occur as B-cells evelop
2. Similar randome rearrangement of TCR a/b chain gene segments occurs in developing T cells
- Gives rise to hugly direverse B and T cells
- This means theres is potential for auto-reactive cells
T and B cells elimination of pathogen process
Where does the adaptive immue responce occur
Secondary lymphoid tissue
How do nieve B and T cells enter lymph nodes
Transendothelial migration
- Enter lymph nodes from High endothelial venules (HEV)
- If after several days they dont encounter any pathogen they return back to blood system via Efferent lymphatics
How do antigens enter the lymph nodes?
-
Debris of pathgens are released by phagocytes
- Inflammatory cytokines (TNFa) stimulate immature, tissue-resident Dendritic Cells ►expression of co-stimulatory molecules
- .Dendritic Cells recognise (PAMP:PRR) and phagocytose pathogen-derived particles and antigens
- Dendritic cells ingests and display small peptide on surface with a MHC complex
- Pathogen debris, antigens and mature denritic cells move to local draining lymph nodes
- Enter lymphnodes via Afferent lymphatics
How are T cells activated
-
T cells can only recognise peptide antigens presented to their TCR by MHC molecules
-
Also known as HLA molecules - able to present many different peptides
- Encoded by highly polymorphic genes
Describe the two classes of MHC molecules
-
MHC class 1 - presented on all nucleated cells
- Present peptide antigens to CD8+ T cells
2. Class 2 MHC - presented on professional Antigen presenting cells
- Dendritic cells, macrophages, B cells
- Present peptide antigens to CD4+ T cells
What are the 2 signals required for T-cell activation
- Antigen specific stimulation signal
-
Denritic presents MHC peptides to the TCR of T cellls
2. Co-stimulatory signal
- B7 molecules : CD28 on T cell
Whats the function of stromal cells in B-zones
Trap opsonised antigens
How do B-cells get activated
they dont need to be presented with MHC peptide
What happens to activates B and T cells
