Lecture 10 9/19/23 Flashcards
What are the three types of antigen presenting cells?
-dendritic cells
-macrophages
-B cells
What are the steps of B cells acting as APCs?
-B cell binds bacteria
-bacterial particle is internalized, degraded, and presented on MHCII
-peptide on B cell MHCII is presented to helper T cell
-B cell is activated to differentiate into plasma cell and produce antibodies
How do B cells capture antigens for presentation?
through their BCRs
Which blood tube is used to collect serum?
red tops
Where is the highest concentration of antibodies found?
serum
Why are antibodies called immunoglobulins?
on serum electrophoresis, the majority of antibodies are found in gamma globulins
What are the effector functions of antibodies?
-block ability of microbes to infect host cells
-inhibit spread of microbes
-inhibit pathologic effects of toxins
What are the components of antibodies?
-two identical heavy chains
-two identical light chains
What are the two regions of an antibody?
-variable region
-constant region
What is the responsibility of the variable region?
binding to specific antigens at the antigen-binding site/paratope
What is the responsibility of the constant region?
complement activation through the classical pathway
What are the two antibody fragments?
Fab and Fc
What does the Fab fragment contain?
antigen-binding site
What does the Fc fragment contain?
complement-activating site
What fragments are produced by papain?
-2 Fab fragments
-1 Fc fragment
What is the hinge region?
a stretch of heavy chains between the Fab and Fc fragments
What is the function of the hinge region?
to provide segmental flexibility
What are the antibody types?
-IgG
-IgM
-IgA
-IgE
-IgD
What heavy chain genes are associated with each type of antibody?
-IgG: gamma
-IgM: mu
-IgA: alpha
-IgE: epsilon
-IgD: delta
What are the two types of light chain?
-kappa light chain
-lambda light chain
Which chain determines immunoglobulin type?
heavy chain
What are the characteristics of IgG?
-most abundant antibody in bloodstream
-Y shape
-only antibody that can cross placenta
-neutralizes toxins and microbes
-activates classical complement pathway
What are the characteristics of IgM?
-five subunits and J chain form a pentamer
-one of the first antibodies produced
-more efficient than IgG at complement activation and microbial clearance
-too large to enter inflammatory sites and cross placenta
What are the characteristics of IgA?
-produced on mucosal surfaces
-important in response to intranasal and oral infections and vaccinations
-prevent attachment of pathogens to mucosal epithelial cells
-forms a dimer from two subunits and J chain
-addition of secretory component forms secretory IgA
-secretory component protects IgA from digestion
-does not activate complement
