Lect 36 - B cells and antibody

Flashcards reviewing key concepts related to B cells and antibodies, including their structure, function, and types.

What is the primary function of B cells?

To develop in the bone marrow and express unique antigen receptors (BCR or secreted antibody).

What type of cells secrete antibodies?

Plasma cells (activated B cells)

What is the significance of memory B cells?

They provide immunological memory, allowing for a faster response upon subsequent exposure to the same antigen.

What happens to the transmembrane region of an antibody when a B cell secretes it?

The transmembrane region is lost at the mRNA level.

What is the main function of the B cell receptor (BCR)?

Binds antigen and partially activates the B cell.

What are the three main functions of antibodies?

Neutralization, Opsonization, and Complement activation.

How does antibody neutralization work?

Antibody binds to structures associated with infection and stops it from interacting with the host cell

What is opsonization?

It makes antigens more easily 'eaten' by phagocytes by tagging them.

How does complement activation lead to cell lysis?

• antibodies bind to surface antigens present in the foreign cell, identifying it as a foreign antigen

• complement proteins are activated upon recognition of antigen-antibody complex

• activated complement proteins assemble into membrane attack complex (MAC)

• MAC forms a pore in the foreign cell’s membrane, disrupting the integrity of the membrane

• due to the pore, uncontrolled flow of water and ions occurs across the cell membrane —> leads to swelling and eventual lysis

What is an epitope?

An antibody binding site.

Which antibody class is most abundant in the blood and crosses the placenta?

IgG

function of IgG?

opsonises / neutralises / activates complement, provides passive immunity, crosses placenta

Which antibody class is found in secretions like tears and saliva?

IgA

function of IgA?

defense of mucous membranes, provides passive immunity, present in breast milk

Which antibody is usually the first produced during the primary immune response?

IgM

function of IgM?

activates complement, targets extracellular bacteria, acts as an antigen receptor

Which antibody is associated with allergic reactions and parasitic infections?

IgE

function of IgE?

immunity to multicellular parasites, allergic reactions

Which antibody's specific function is largely unknown, but it acts as an antigen receptor?

IgD

function of IgD?

acts with IgM as an antigen receptor

What do memory cells express as BCR, but do not secrete?

Antibody

How long does it take for sufficient antibody to be produced during primary immune response?

Around 7-14 days.

primary immune response?

• low amount of antibody produced

• mainly IgM

Which antibody is mainly produced in a secondary immune response?

IgG

secondary immune response?

• basis of the success of vaccination

• relies on memory B cells

• mainly IgG with some class swicthing to IgA and IgE

How long does it take for sufficient antibody to be produced during secondary immune response?

2-3 days