S7 Adaptive Immune System Part 2 Flashcards
When do antigen presenting cells mature?
When they ‘capture’ an antigen
Where in lymphoid tissue do T cells become activated, B cells become activated and where do they meet?
- parafollicular cortex (T cell zone)
- lymphoid follicle (B cell zone)
- edge of follicle
Where are B and T lymphocytes produced? Where do they mature?
Produced in bone marrow
T cells - mature in thymus
B cells - mature in tissues following contact with the antigen
Where do B and T lymphocytes accumulate?
In lymphoid tissues e.g. MALT, lymph nodes and spleen
What are the main 3 lymph nodes?
- cervical (neck)
- axillary (armpit)
- spleen (inguinal)
What is lymphadenopathy?
Swelling that occurs in lymph nodes/tissues/etc when B and T cells are activated by the antigen and start proliferating
How are antigens recognised by T lymphocytes?
Antigens are recognised by T cell receptors (TCR)
- CD4+ T cells recognise peptides presented by MHC class II molecules
- CD8+ T cells recognise peptides presented by MHC class I molecules
What is a T cell receptor (TCR) like?
- alpha and beta chains (variable region)
- CD3 complex
- accessory molecules - CD4 or CD8
How are T lymphocytes activated?
By co-stimulation
* a co-stimulatory protein is needed to fully activate a T cell
What activates CD4+ T cells to produce the different variants?
Activated by chemical mediator e.g. IL-12/4/1/6/10 or TGF-beta
What do TH1 CD4+ T cells cause stimulated by IL-12?
- CD8+ T cells to differentiate
- macrophage recruitment and activation
- stimulates B cells to produce IgG or IgA
This is cell mediated immunity (against extracellular pathogens - bacteria, viruses, fungi)
What do TH2 CD4+ T cells cause stimulated by IL-4?
- stimulate B cells to produce IgE
- activate eosinophils to kill pathogens
- activates mast cells against allergies
This is humoral immunity (against extracellular pathogens - parasites, worms)
What do TH17 CD4+ T cells cause stimulated by IL-1/6?
- recruitment and activation of neutrophils
What do THreg CD4+ T cells cause stimulated by IL-10/TGF-beta?
- tolerance
* immune suppression
What is required to activate effector CD8+ T cells?
TH1 (for activation of effector CD8+ T cells from naive CD8+ T cells)
If an unaffected cell has MHC I molecules presenting self-antigens will this be detected by cytotoxic lymphocytes?
No
How are antigens recognised by B lymphocytes?
By B cell receptors (BCR) which are membrane bound antibodies and are unique and specific for each cell
What types of antigen to B lymphocytes recognise?
- macromolecules (proteins, polysaccharides, lipids, nucleic acids)
- small chemicals
What is required for activation of B lymphocytes?
Multiple signals
- BCR engagement - signal transduction
- TCR engagement - this is antigen specific
- Cytokine release
Why do you need T helper cells involved in B lymphocyte activation?
If didn’t have T helper cells, would only be able to produce IgM antibodies, T helper cells are involved in the switching of antibody production to e.g. IgG due to the CD40L on T cells
Production of which antibodies is thymus-dependent?
IgG, IgE and IgA
Why do we have booster vaccinations?
To increase the amount of IgG (better protection than IgM) - in secondary response
How can you tell if exposure to an infection is acute of chronic?
By the type of antibody present
- acute - more IgM
- chronic - more IgG
What is the role of antibody IgA?
Involved in mucosal immunity e.g. GI tract and respiratory tract immunity
