Adaptive immunity part 2 Flashcards
Where do APC migrate to to present pathogen to T cells?
Parafollicular cortex in lymph tissue
there are lots of T cells here
Where do B cells communicate with T helper cells to mature?
Edge of follicle
Where do you find most Naive B cells?
Lymphoid follicle (B cell zone)
What do CD4 cells become?
T helper cells (recognise MHC class 2)
What do CD8 cells become?
Cytotoxic T cells (recognise MHC class 1)
Where are B and T lymphocytes produced and mature?
Produced in bone marrow
T cells mature in thymus
B cells mature after contact with antigen
Where are B and T cells found?
Blood (70% T of T cells, 5-15% of B cells)
Where do T and B cells accumulate?
Lymphoid tissue
mucosa associated lymph MALT, lymph nodes, spleen
When does lymphadenopathy occur?
Swelling from activation of B and T cells by antigen
Where are common lymph nodes that you can notice enlargement found?
Neck (cervical)
Armpit (axillary)
Groin (inguinal)
What receptors do T cells possess to recognise antigen?
T cell receptor (TCR)
Parts of TCR
alpha and beta subunit
CD3 complex
either CD4 OR CD8 accessory molecule
2 regions of TCR
Variable and constant
What allows for diversity of antigen receptors?
Combinatorial diversity (random combinations of the genes to form antigen receptor)
What does activation of T lymphocytes require?
Co-stimulation (2 signals are needed)
T signals required in activation of T lymphocytes
Signal 1: MHC class 1/2 binding to TCR
Signal 2: B7 protein on APC binding to CD28 on T cell
Signal 3: cytokines
What occurs when APC cells are matured?
Express B7 protein that CD28 on T cell can bind to
T helper cells involved in cell mediated immunity (intracellular pathogens)
TH1 (T helper cell 1)
T helper cells involved with Humoral immunity (against extracellular pathogens eg parasites/worms)
TH2 and TH17
Humoral immunity
Defence against extracellular pathogens
Cell mediated immunity
Defence against intracellular pathogens
Other T helper cell required
T regulator (tolerance and immune suppression)
Cells involved in TH2 and TH17 pathway
TH2: B cells (IgE and IgG), Eosinophils, Mast cells
TH17: Neutrophils
Cells involved in TH1 pathway
CD8 T cells differentiate
Macrophages
B cells (IgG and IgA)
Effector functions of CD8 T cells
Need TH1 and cytokines to activate into cytotoxic T cells
What does cytotoxic T cell do?
Kill all infected cells expressing the viral peptides that MHC class 1 present
What else can naive CD8 cells become?
Memory CD8 cells
How are antigens recognised by B cells?
B cell receptor (BCR)
what is BCR?
Membrane bound antibody
Unique specificity for each cell
Regions of BCR
Variable region
Constant region
How are antigen receptors diverse?
Combinatorial diversity (random combo of genes)
What antigens are recognised by B cells?
Macromolecules (lipids, proteins, nucleic acids)
and Small chemicals
What do T cell recognise?
Only peptides presented by either MHC class 2 (CD4) or MHC class 1 (CD8)
Signals required to activated B cell
Signal 1: BCR engagement
Signal 2: TCR engagement
Signal 3: Cytokines, CD40 activation
BCR engagament signal 1
Antigen processing and presentation
Increased B7 costimulators
TCR engagement signal 2
Antigen specific
B7 co-stimulation
What occurs after activation of B cell?
Antibody production
Affinity maturation in antibody (stronger)
Memory B cells
IgM
First antibody produced
T helper cell independent
IgG, IgA, IgE
T helper cell dependent
Isotope (heavy chain switch) switch from IgM
Memory B cell significance
Upon re challenge give faster, stronger and longer antibody response
Regions of antibody
Top arms: Fab region Bottom leg: Fc region Inner top arms: light chain Outer top arms: heavy chain Ends of top arms: Antigen binding region Area connecting arms and leg: Hinge region
What does heavy chain determine?
Isotope of antibody (IgG/IgM)
What do antbody isotopes switch between?
Originally IgM
Then IgG, IgA or IgE (thymus dependent)
What happens to antibody response if body is exposed to antigen for a second time?
Faster Stronger Longer duration Higher affinity Isotope switch (IgM to IgG)
IgG functions
Fc dependent phagocytosis
Complement activation
Neonatal immunity
Toxin/virus neutralisation
IgE functions
Immunity against helminths
Mast cell degranulation (allergies)
IgA function
Mucosal immunity
IgM function
Complement activation
Medical achievements from adaptive immune response
Disease prevention (vaccination) Immunoglobulin therapies (for immune deficiency) Immediate protection (transfer antibodies) Diagnostic tests (Infectious diseases, autoimmune, HLA and blood types)
