Cell Imm Methods MCQ Material

What is an antibody?
Produced in response to non self by plasma B cells. Each plasma B cell identical antibodies bind to same epitope. Many plasma B cells activated by same immunogen produce different antibodies because different epitopes.

B cell activation/Clonal selection
Requires antigen bind to BCR and co stimulation by CD40 (T cell dependent) or danger signalling (T cell independent)
Results in clonal expansion and diff into plasma or memory cells
T cell dependent -
T cell independent - CD40 on cell surface. Ag binds to BCR, ingested and processed, Ag presented on MHC II, BCR recycled, activates Th cell, gives co signal, memory and plasma cell increase

Plasma or Memory Cell
Plasma - Ab factory (2000 Ab per second) short lived
Memory - Produced mainly be T cell dep activation. Larger pop than naïve B cells, easier activated than B cells. Ab more specific than B cells - affinity maturation. Class switching done.

Class Switching
All B cells initially mainly IgM and some IgD. IgM = pentamer. Monomer = BCR
As B cells mature switch isotope controlled by cytokines. Each isotope different properties.

Ab Functions
Do not kill/remove pathogens alone
Recognise/bind Ag and trigger effector function
Isotope important, Fc region determines effector function
Functions: opsonisation, complement activation, ADCC, agglutination, degranulation

Complement Fixation
IgG (two IgG needed) and IgM needed
Fc regions activate complement cascade when Ag bound
Disrupts pathogen membrane
Can be opsonised for inc phagocytosis

Opsonisation
Promotes phagocytosis by neutrophils and macrophages
Fc bind on phagocyte membrane

Agglutination
Ab bind two Ag (or more if multivalent i.e IgM)
Pathogens bound together, prevent their normal functions, more efficient phagocytosis

ADCC - Antibody Dependent cell mediated cytotoxicity
Ab bind to Ag, Fc region bound to effector cell

Degranulation
IgE only. Unusual, Fc primes effector cells before binding to Ag. Granulocytes release granules by cross linking Fc receptors on granulocyte

IgM - good complement, opsoniser, agglutinator
IgA - Protects mucosal, resistant stomach acid, secreted in milk
IgG - ok complement fixer, good opsoniser, induce ADCC, cross placenta
IgE - Defend against parasites, induce degranulation, role in allergy

Fc Receptors
Cells different Fc receptors each cell
Bind to Ab Fc initiates Ab mediated effector function
Each isotope different Fc region,
Fc receptors for polymeric immunoglobulins - imp for transporting IgA dimers and IgM multimers across epth membrane
Neonatal Fc receptor transfer IgG across placenta

Ab uses
Respond infection and diagnosis
Diagnosis - specific, easily manipulated i.e tagging. I.e Fluorescent in flow cytometry. HRP in ELISA

	Created by Rebecca Marsden almost 9 years ago

Undergrad Cell and Immunological Methods Note on Cell Imm L1 ROUGH NOTES, created by Rebecca Marsden on 24/02/2017.

Cell Imm L1 ROUGH NOTES