Infection & ResponseDefinitions
Key Definitions
Part of Adaptive Immunity and Antibodies — GCSE Biology
This definitions covers Key Definitions within Adaptive Immunity and Antibodies for GCSE Biology. Specific immune responses, antibody production, lymphocytes, memory cells It is section 8 of 15 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.
Topic position
Section 8 of 15
Practice
20 questions
Recall
25 flashcards
Key Definitions
Antigen: A foreign molecule (usually a protein on the surface of a pathogen) that triggers an immune response. Each antigen has a unique molecular shape that the immune system recognises.
Antibody: A Y-shaped protein produced by plasma cells (differentiated B lymphocytes) that binds specifically to one antigen. Antibodies tag pathogens for destruction by phagocytes and neutralise toxins.
Antitoxin: An antibody that binds to and neutralises a toxin produced by a pathogen, preventing it from causing harm to the body.
B lymphocyte (B cell): A type of white blood cell that, when activated by a specific antigen, divides to produce plasma cells (which secrete antibodies) and memory B cells.
T lymphocyte (T cell): A type of white blood cell. Helper T cells coordinate the immune response and activate B cells. Killer T cells directly destroy infected or abnormal cells.
Plasma cell: A differentiated B lymphocyte that acts as an antibody factory, secreting thousands of antibody molecules per second specific to one antigen.
Memory cell: A long-lived lymphocyte (B or T cell) produced during a primary immune response that remains in the body and enables a faster, stronger secondary response on re-exposure to the same antigen.
Primary immune response: The slow initial response to first exposure to an antigen. Takes 5–10 days to produce significant antibody levels; produces memory cells.
Secondary immune response: The rapid, strong response to subsequent exposure to the same antigen. Memory cells respond within 1–3 days and produce higher antibody levels; often prevents disease symptoms entirely.