Cambridge International A Level Biology 9700 IMMUNITY — Exam-Style Summary Notes

Vocabulary-style flashcards covering the key mechanisms, cell types, and definitions of the immune system based on A Level Biology summary notes.

Skin

Acts as a physical barrier with keratinised cells that make it difficult for pathogens to enter.

Mucous membranes

Membranes where mucus traps pathogens and particles.

Ciliated epithelial cells

Cells with cilia that move mucus towards the throat to be swallowed.

Stomach acid

Low pH environment that kills many pathogens entering in food.

Inflammation

Non-specific response where damaged cells release histamine, causing blood vessels to dilate and become more permeable.

Phagocytosis

A non-specific process where phagocytes engulf and digest pathogens using lysosomes.

Antigen

A molecule or part of a pathogen recognised as foreign by the immune system.

Antibody

A soluble protein produced by B lymphocytes or plasma cells that binds specifically to a complementary antigen.

Specificity (Antibody)

The characteristic where an antibody's variable region has a complementary shape to its antigen.

Antigen–antibody complex

The binding of an antibody to an antigen which can neutralise toxins/viruses or mark a pathogen for destruction.

B lymphocyte

A cell type involved in specific immune responses involving antibodies; can form memory cells.

Plasma cell

A differentiated B cell that secretes large quantities of antibody.

Memory B cell

An immune cell that remains after the primary response to enable a faster, larger secondary response.

T helper cell

A cell that recognises antigen presented by an antigen-presenting cell and releases cytokines to activate other immune cells.

T killer cell

A cell that destroys infected or abnormal body cells by inducing cell death.

Memory T cell

A cell that remains after the primary response and contributes to faster secondary responses.

Clonal selection

The process where a lymphocyte with a complementary receptor is selected by a specific antigen.

Clonal expansion

The process where a selected lymphocyte divides by mitosis to produce many genetically identical cells.

Antigen-presenting cell (APC)

A cell that displays pathogen-derived antigen on its cell-surface membrane.

Primary immune response

The immune response to the first exposure of an antigen, which is slower and produces lower antibody levels due to few/no initial memory cells.

Secondary immune response

The faster, stronger, and longer immune response occurring when the same antigen is encountered again, driven by memory cells.

Vaccine

A harmless form or source of antigen, such as weakened or inactivated pathogen, used to produce immunological memory.

Herd immunity

Protection provided to susceptible individuals when a sufficiently high proportion of a population is immune, reducing transmission.

Active immunity

Immunity where antibodies are made by the person's own immune system, leading to the production of memory cells and long-term protection.

Passive immunity

Short-term immunity resulting from antibodies provided by another source, such as maternal or injected antibodies, without the production of memory cells.

Monoclonal antibodies

Identical antibodies produced by a single clone of B cells that bind to one specific antigen.

Hybridoma

A cell formed by fusing a B lymphocyte producing a desired antibody with a tumour cell, allowing for repeated division and antibody production.