Lecture 6 - Antibodies Flashcards
definition of an immunoglobulin
protein used by immune system to neutralize foreign objects like bacteria and viruses
describe the structure of antibodies
heavy and light chain
heavy = 2 chains of constant effector region at bottom, 1 chain with Ag-binding site on each arm of the Y
light = 1 chain with Ag-binding site on each arm of the Y
what happens if we engineer an Ab to lose the Fc portion and keep Ag-binding region?
receptor-Ab interaction without activating immune system
what are the complementarity-determining regions?
part of the variable chains where the Ab binds to the Ag
what is a paratope?
a set of CDRs
CDRs are the most _______ part of Ab, therefore:
CDRs are the most variable part of the Ab, therefore they are crucial to the diversity of Ab
how many CDRs are there on an immunoglobulin?
each variable domain has 3 CDRs (CDR1/2/3) and sicne there are 2 variable domains, an Ab has 6 CDRs
how many CDRs are there on an IgM?
60 CDRs
how can we use CDRs in drug development?
modify CDRs to have specificity for certain epitope
what are polyclonal Ab?
what are they made by?
how do they bind Ag?
mixture of heterogenous Ab
produced by diff B cell clones in the body
can recognize and bind to many epitopes of a single antigen (many CDRs involved!)
what are monoclonal Ab?
what are they made by?
how do they bind Ag?
one type of Ab
produced by identical B cells that are clones from a single parent cell
can only recognize one epitope of an antigen
how are antibodies involved in the complement system?
Fc portion can bind complement proteins and help the immune cell recognize pathogen thru complement cascade
how are antibodies involved in macrophages?
Ab binds Fc receptor on macrophages –> Ab bind pathogen and opsonize it so the macrophage can phagocytose it
describe Ab in RSV-infected cell
cell infected with RSV expresses specific protein on its surface –> allows for production of Ab that binds the protein –> NK cell recognizes the Fc and kill the infected cell
what is the scFv fragment?
made of the variable domain of the heavy and light chains of a mAb (i.e. the Ag-binding part)
when we chop them up for therapeutic purposes, we express as 1 polypeptide chain with a linker btwn the chains
what is the Fab fragment?
variable domain of each chain and the first constant region (the entire upper part of the Y)
how do our bodies make Ab? (3 steps)
- B cell activated when it meets Ag
- B cell presents Ag to matching T cell
- T cell secretes cytokines to help the B cell multiply and mature into Ab-producing plasma cells
2 general ways to produce engineered Ab
- inject Ag into rabbit –> B cells activated and make pAb –> collect antiserum containing pAb
- inject Ag into mouse –> fuse spleen cells with immortlaized myeloma cells –> B cells can now replicate well and make lots of mouse Ab (can be pAb or mAb)
what is phage display?
genetically modify phages so that they can encode variable region that binds epitope –> phages can replicate easily so will make lots Ab (highthroughput!)
test the Ab against Ag –> find the best Ab, put into B cells so they can make the Ab to be used
how can we use a transgenic mouse to make human Ab?
humanize mouse to make human B cells and therefore human Ab
how can we use human B cells to make Ab?
immortalize a B cell from human and screen for specific Ag
describe PSEUDOMONAS AERUGINOSA
- gram negative opportunistic bacteria
- causes pneumonia in ventilated patients –> disrupts lung barrier and causes bacteremia
- multi-drug resistant!
what is the role of T3SS in PA?
what happens if it is deleted?
injects mutliple virulence factors into host cells and is used for pore formation
deleted –> bacteria less infective
what is PsI exopolysaccharide?
allows for:
- COLONIZATION –> promotes bacterial aggregation and tissue adherence
- PERSISTENCE –> component in biofilm formation/maintenance
also involved in immune evasion
