Lec 3 - Adaptive Immunity - Humoral Flashcards
Where do lympocytes come from and where do B and T cells mature?
stem cells in the bone marrow.
b cells mature in BONE MARROW.
t cells mature in THYMUS
What are the B/T cell receptros?
B cell receptor - antibody.
Tcell - T cell receptor
Where does antigen in/dependent differentiation take place?
in - central lympohoid tissue
dependent - peripheral
What are the infections that B/T cells are effective against?
- B cells - extracellular bacteria, 2ndry viral
- T - intracellular - viral, parasitic, bacterial
Describe the clonal selection hypothesis and give the 2 types of cells that result
- B cell with specific antibody that binds the specific antigen differentiates into MANY plasma cells
- these plasma cells all produce the same Ab
- B cells can also differentiate into memory cells - that do not currently poruce Abs unless 2ndry infection occurs
Antibodies may be ____ of infections
diagnostic
What is an antigen?
molecule (protein, carb) that binds antibodies
specific Ab binds an ANT
Draw a schematic of an Ab and label it
dont forget the hinge region
What does Fc/Fab stand for and state what they bind
- Fc - Fragment crystallisable - binds Fc receptors & complement
- Fab - fragment antigen binding - binds antigen
Describe the V and C regions
- encoded for by different exons
- V - bind different atigens
- C - constant for a given Ab H chain / L chain type
How can different Ab specificities arise?
multiple V region exons can recombine to give different specifciites
Describe IgG/M/A/D/E
- IgG - 2ndry responses, main Ab in serum and tissues
- IgM - 1ry responses
- IgA - important in secretions & protecting mucosal surfaces
- IgD - ?
- IgE - allergy and large parasites , few
Give the 2 additional types of Ab L chains and state why they are special
- kappa (K) and lamda
- can belong to different classes eg IgGK (ie aren’t class restricted)
Draw a graph that illustrates the 1ry/2ndry response
What is classs switching?
- as V and C regions encoded by separate exons, allows the V regions to recombine to gene regions next to diffeent C regions
- this means that same V region, that used to be on IgM Abs, can now exist on IgG therefore has a different effector function
Describe afinity maturation
- somatic hypermutation can occur in the V regions leading to a higher binding affinity for the antigen
- almost like natural secletion
- this mutation is selected for
Describe the GENERIC effects of immunoglobuilin on pathogens
- bind to and reduce nutrient uptake
- neutralise toxin eg Diptheria
- bind to and prevent adhesion to other surfaces
- promote agglutination of bacteria - easier for phagocytosis
Describe the effects of immunoglobulin on pathogens that RELY ON FC REGION
- induce phagocytosis by phagocytes with Fc receptors
- complement activation leading to cell lysis
- enhanced killing by NK cells (ADCC)
Which complement molecule is activated when it binds to the Fc region of 2 Abs and what does this lead to?
C1q - leads to inflammation (phagocytes etc) , opsonisation and cell lysis
What is the protein that prevents host cells being susceptible to MAC by C9?
CD59 - prevents assembly og the last componenet in MAC formation (C9)
Give an example of a bacterial protein that binds the Fc region of IgG and what does this do?
- Staph aureus
- protein A binds Fc region
- prevents phagocytes binding to Fc region of bound IgG antibodies therefore prevents opsonisation
What is ADCC and describe it
- antibody dependent cell mediated cytoxicity
- Abs mediate ADCC of NK cells
- NK cells have IgG receptors binding to IgG on bacterial cells stimulates perforin release to punch holes in cell wall and allow contents of granules to be secreted in and induce apoptosis
