Adaptive Immunity VCE Biology 3/4

Unit 4 AOS 1

hat is the innate immune response?

The rapid, non-specific second line of defence; it has no immunological memory.

What is the adaptive immune response?

The specific third line of defence; it is slower initially and retains memory for faster responses on re-exposure.

What are the key features of adaptive immunity?

Antigen specificity, a slower initial response, and immunological memory.

Which cells are the main lymphocytes of adaptive immunity?

B lymphocytes, helper T lymphocytes and cytotoxic T lymphocytes.

Where do lymphocytes reside according to the notes?

In lymph nodes, where they can encounter specific antigens.

What is the role of the lymphatic system in adaptive immunity?

It transports lymph, pathogens and antigen-presenting cells to lymph nodes.

What is the role of lymph nodes?

They are sites where antigens are presented and matching B and T lymphocytes are selected and activated.

What are antigen-presenting cells (APCs)?

Cells such as dendritic cells and macrophages that engulf pathogens and display their antigens on MHC proteins.

How do dendritic cells and macrophages help activate helper T cells?

They phagocytose pathogens, display antigens on MHC-II, travel to lymph nodes and bind matching helper T-cell receptors.

What is clonal expansion?

Division of an activated lymphocyte to produce many cells with the same antigen specificity.

What is the role of helper T lymphocytes?

They release cytokines that activate B lymphocytes and cytotoxic T lymphocytes.

Where are helper T lymphocytes produced and matured?

Produced in bone marrow and mature in the thymus.

What is humoral immunity?

Using antibodies to fight infection in body fluids.

Where are B lymphocytes produced and matured?

They are produced and mature in the bone marrow.

How is a B lymphocyte selected?

An antigen binds directly to a B cell’s complementary surface antibody receptor.

How is a selected B lymphocyte activated?

Cytokines released by activated helper T lymphocytes activate it.

What do activated B lymphocytes become?

They undergo clonal expansion and differentiate into plasma cells and memory B lymphocytes.

What is the role of plasma cells?

They produce and release antibodies specific to the antigen.

What is the role of memory B lymphocytes?

They remain in the body and enable a faster, larger antibody response on later exposure to the same pathogen.

What is an antibody’s basic structure?

A protein with quaternary structure, two identical heavy chains and two identical light chains.

What are antibody variable regions?

Regions with varied forms that create antigen-binding sites specific to different antigens.

What is the antibody constant region?

The relatively consistent region that can take one of five forms, according to the notes.

What is an antigen-binding site?

The part of an antibody whose shape is complementary to a specific antigen.

What is agglutination?

Antibodies clump antigens or pathogens together.

What is neutralisation by antibodies?

Antibodies prevent pathogens from binding to body cells.

What is opsonisation?

Antibodies make antigens or pathogens more susceptible to phagocytosis.

How does the primary antibody response differ from the secondary response?

The primary response is slower and smaller; the secondary response is faster and produces more specific antibodies.

Why is the secondary immune response faster?

Memory B lymphocytes recognise the pathogen and rapidly expand into antibody-producing cells.

What principle underlies vaccination?

Exposure generates memory lymphocytes, enabling faster and larger responses to later exposure.

What is cell-mediated immunity?

The response in which cytotoxic T lymphocytes destroy infected body cells.

Where are cytotoxic T lymphocytes produced and matured?

Produced in bone marrow and mature in the thymus.

How are cytotoxic T lymphocytes selected?

A cytotoxic T cell with a complementary receptor recognises non-self antigen presented on MHC-I.

How are selected cytotoxic T lymphocytes activated?

Cytokines released by helper T lymphocytes activate them.

What is the role of MHC-I proteins?

All nucleated cells display MHC-I proteins, normally presenting samples of self-antigens; infected cells can display non-self antigens.

What is the role of MHC-II proteins in the notes?

Antigen-presenting cells display non-self antigens on MHC-II to helper T lymphocytes.

How do cytotoxic T lymphocytes kill infected cells?

They recognise non-self antigens on MHC-I and initiate apoptosis, or controlled cell death.

What are memory cytotoxic T lymphocytes?

Long-lived cells that remain after clonal expansion and help respond to future infections.

What is active immunity?

Immunity produced by a person’s own immune response after exposure to an antigen; it can create memory.

What is passive immunity?

Immunity gained by receiving antibodies made by another individual; it provides antibodies without the recipient making the memory response.

What is natural immunity?

Immunity acquired through naturally occurring exposure or transfer, rather than a medical intervention.

What is artificial immunity?

Immunity acquired through a medical intervention, such as vaccination or administered antibodies.

How do active and passive immunity differ?

Active immunity involves the person making their own response; passive immunity involves receiving ready-made antibodies.

How do natural and artificial immunity differ?

Natural immunity occurs without a medical intervention; artificial immunity results from a medical intervention.

Why can mismatched blood groups cause problems?

Antibodies may bind to foreign blood-group antigens, causing an immune reaction.