AQA Biology - Immune System

Vocabulary flashcards reviewing pathogens, antigens, white blood cell actions, lymphocyte types, primary and secondary immune responses, and non-specific defences.

Pathogen

A microorganism that causes disease, such as bacteria, viruses, fungi, and protists.

Antigen

A molecule on the surface of a cell or pathogen that can be recognised by the immune system.

Phagocytosis

A defence process where a white blood cell surrounds and engulfs a pathogen, forming a vesicle around it, after which digestive enzymes break down and destroy it.

Antibodies

Proteins produced by lymphocytes that have a specific shape complementary to a particular antigen and bind specifically to it.

Agglutination

The process where antibodies bind pathogens together into clumps, making them easier for phagocytes to engulf.

Antitoxins

Antibodies that bind to and neutralise toxins produced by pathogens.

Lymphocytes

White blood cells involved in specific immune responses, including B cells and T cells.

Clonal Selection

The process where a specific lymphocyte with a receptor complementary to an antigen is selected and activated.

Clonal Expansion

The process where an activated lymphocyte divides by mitosis to produce many genetically identical cells.

B Cells

Lymphocytes that differentiate into plasma cells to produce specific antibodies.

Plasma Cells

Activated B cells that produce and secrete large quantities of antibodies.

Helper T Cells

T cells that release cytokines to activate other immune cells, including B cells.

Cytotoxic T Cells

T cells that destroy infected or abnormal body cells.

Memory Cells

Long-lived B and T cells that remain after an infection and allow a faster response upon re-exposure to the same antigen.

Primary Immune Response

The initial response where the immune system first recognises an antigen, activates specific lymphocytes, and produces antibodies and memory cells.

Secondary Immune Response

A faster and stronger response occurring upon re-exposure to an antigen, driven by existing memory cells rapidly dividing to produce antibodies.

Non-Specific Defences

Immune defences that protect against many different pathogens rather than one specific pathogen.

Skin (Immune Function)

A non-specific defence that forms a physical barrier against pathogens and produces antimicrobial substances.

Mucus

A non-specific defence fluid that traps pathogens before they can reach deeper tissues.

Cilia

Hair-like structures in the airways that move mucus containing trapped pathogens towards the throat to be swallowed.