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 12 of 18 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.
Topic position
Section 12 of 18
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. The term comes from "antibody generator." Each antigen has a unique molecular shape.
Antibody: A Y-shaped protein produced by plasma cells (B lymphocytes) that binds specifically to one antigen. Antibodies tag pathogens for destruction, neutralise toxins, and cause agglutination (clumping).
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 involved in cell-mediated immunity. Helper T cells coordinate the immune response; cytotoxic T cells directly kill infected or abnormal cells.
Plasma cell: A differentiated B lymphocyte that acts as an antibody factory, secreting thousands of antibody molecules per second against a specific 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.