Adaptive immunity- effector stage Flashcards
B and T lymphocytes are produced by the
bone marrow
where do T cells mature
in the thymus
where do B cells mature
in the tissues following contact with antigen
B cells make up
5-15% of lymphcytes
T cells make up
70% of lymphocytes
where do B and T cells accumulate
o Mucosa-associated lymphoid tissue (MALT)
o Lymph nodes o Spleen
lymphadenopathy
occurs when b and T cells are activated by the antigen
T cell receptors carry out
antigen recognition
TCR structure
α and β chains o CD3 complex
o Accessory molecules (CD4 or CD8)
diversity of TCR
huge diversity- can recognise all pathogens
- Combinatorial diversity (>10^16)
TCR recongise
peptides presented by MHC I and MHC II
subtypes of T lymphocytes
o Helper T cells (CD4+) recognise peptide
presented by MHC class II molecules
o Cytotoxic T cells (CD8+) recognise peptide
presented by MHC class I molecules
activation of T lymphocytes: role of costimulation
1) Signal 1: APC present pathogen peptide on its MHC (I or II depending on T cell type (CD8/4))
2) Signal 2: CD28 on complexes with B7 on APC
3) Signal 3: APC releases cytokines which stimulates the T cell
during T cell activation what happens to CD4 + T cells
they become T helper cells e.g. Th1 and Th2
during T cell activation what happens to CD8+ T cells
they become cytotoxic T cells (CTL)
Activation of T helper cell response (CD4+ T cells)
APC will release cytokines which will stimulate the naive CD4+ T cell to become a specific type of T helper cell (H1, TH2, TH17, Treg)
TH1
- cell mediated immunity- for intracellular and extracellular pathogen*
- stimulate CD8 T cell differentiation
- recruitment and activation of macrophages
- stimulate production fo IgG or IgA from B cells
TH2 and TH17 mediate
humoral immunity- defence against extracellular pathogen (parasite, worms)
TH2
- stimulate B cells to produce IgE
- stimulate eosinophils to kill pathogens
- Allergic response from mast cells
TH17
recruitment and activation of neutrophils
Treg
tolerance and immune suppression
effector functions of CD8 T cells
1) APC binds to both Naive CD4 T cells and naive CD8 T cells
2) The CD4 T cell matures to become a TH1 cell
3) TH1 cell stimulates the Nazxive CD8 T cell to become and effector CD8 T cell
4) CD8 T cell becomes a cytotoxic T cell (CTL)
5) CTL moves to peripheral tissue and jills all infected cells (senses infected cells by their MHC class I)
6) Other naive CD8 T cells will become memory CD8 T cells
in general CD4 T cells
increase phagocytosis and increase production of antibodies by plasma cells
B cells receptors are
membrane bound antibodies
- unique specificity for each cell
diversity of antigen receptors
combinatorial diversity (>10^11)
forms of antigens recognised by BCR
macromolecules (proteins, polysaccharides, lipids, nucleic acid)
small chemical
activation of B cells requires
multiple signals
activation of B lymphocyte signals
1) 1st signal: BCR engagement
- signal transduction
- antigen processing and presentation
- increased B7 costimulators
2) 2nd signal: TCR engagement
- antigen specific
- role of B7 costimulators
3) 3rd signal
- Cytokines
- CD40
4) proliferation and differentiation
5) Antibody production
6) heavy chain swithcing
outcome of B lymphocyte production
IgM production is T helper independent
IgG, IgA, IgE production is T helper dependent (isotope switching)
affinity maturation in antibody production
occurs after prolonged and repeated exposure
memory B cells
upon re-challenge can give a faster, stronger and longer antibody response
effector T cells are required for
production of of IgG, IgE and IgA (thymus dependent antibodies
after the body is exposed to an antigen e.g. after first injection which antibody dominates the total antibody count
IgM
IgM is involved in
complement activation
after second exposure to antigen e.g. after second vaccine which antibody dominates the total antibody count
IgG
IgG is involved in
Fc-dependent phagocytosis Complement activation Neonatal Immunity Toxin/virus neutralization
IgA involved in
mucosal immunity
IgE involved in
Immunity against helminths
Mast cell degranulation (allergies)
medical achievements derived from the study of the adaptive immune response
- disease prevention
- immunoglobulin therapies
- immediate protection
- Diagnostic tests (antibody-based)
disease prevention
vaccination (or active immunisation)
immunoglobulin therapies
immune deficiencies
immediate protection
passive immunisation (antibody transfer)
diagnostic tests (antibody-based)
- infectious diseases
- autoimmune diseases
- blood type and HLA type
DiGeorge syndrome is an immune deficiency resulting from an impaired thymic development. Which of the following immune components will be affected in these patients?
- B cell development
- Complement pathways
- T cell development
- T cell and B cell function
T and B cell function
CD4+ T cells that respond to intracellular pathogens by recruiting and activating phagocytic cells are termed
- Antigen presenting cells
- Cytotoxic T lymphocytes
- Th1 4. Th2
Th1
Patients who do not have CD40L on their T cells (due to mutations) will likely produce an antibody response to staphylococcus aureus composed of:
1. IgG 2. IgM 3. IgA 4. IgE
- IgM
