Cell and Antibody Immunity Flashcards
List the four main types of antibody-mediated effector functions.
Neutralization
Complement fixation
Opsonization and phagocytosiss
ADCC: Antibody dependent cell-mediated cytotoxicity
What does neutralizing antibodies do?
How could this work? List 5 ways.
Prevents pathogens from initiating infection.
- Bind pathogen surfaces and prevent receptor interaction.
- Bind receptor and prevent pathogen interaction
- Block interactions between pathogen and endosomal membrane proteins.
- Interfere with conformational changes required for viral-host membrane fusion
- Inhibit release of progeny pathogens
What is the secondary function of neutralizing antibodies? How is this useful?
It can protect against toxins like bacterial ones from tetanus or venom from snake bites.
Serum therapy is still the only way to treat venom poisoning. Anti-venoms are still prepared by fragmentation of polyclonal antibodies isolated from hyper-immunized horse serum.
How does complement fixation occur?
MAC attack! - forms a MAC (membrane attack complex) and forms pores in the target cell/virion membrane causing influx of extracellular fluid and the lysis of the target.
What does opsonization literally mean?
How does opsonization work?
To make tasty.
It refers to the ability of antibodies to enhance the engulfment of pathogens by phagocytes. Antibodies interact with Fc receptors on the surface of phagocytes. Induces antigen internalization and destruction by phagocyte.
What does ADCC mean and how does it work?
Antibody-dependent cell-mediated cytotoxicity.
antibody-Ag complexes are bound by Fc receptors on NK cells and granulocytes which allows the cell to adopt Ag specificity.
Promotes direct cytotoxicity towards target cell and releases cytotoxic mediators such as perforin and granzyme B
How could ADCC be used therapeutically to fight infection or cancer?
It could be fed specific Ag-antibodies that would target cancer cells to kill them
Describe Fc receptors and signalling.
Fc receptors must be cross-linked (oligomerized) by binding complex antibodies in order to be activated. FcR signalling is similar to BcR signalling and uses SKY, LYN, and BTK signalling cascade.
Many types of receptors each with specific Ab isotype and different receptors on diff cell types = different cell functions.
Describe cytotoxic effector responses.
By what are they mediated?
Trigger apoptosis in target cell and cear viruses and bacteria from infected cells. Also eliminates tumours.
CD8+ T cells, NKT cells, and NK cells.
How to Th cells assist in CTL activation?
CD8+ T cells have CD40 and Th cells have CD40L which activates CTLs and causes them to proliferate and migrate.
How to IS perform in CTL function?
CTLs for IS to mediate target cell killing. The MTOC, Golgi, and secretory granules with perforin/granzymes are polarized towards other cell. Contraction of granules and extrusion of contents into the synaptic cleft.
Describe possible CTL activity against neurons. What illness is caused by this phenomenon?
CTLs can mediate axonal transection of neurons which results in the disruption of neural signalling, Wallerian degeneration of axon, and eventually nerve death.
Multiple Sclerosis
