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Immune System Flashcards
Free Medical Science Revision Cards
From innate defences to adaptive immunity and the role of B and T lymphocytes, these free Medical Science flashcards give you a thorough grounding in how the immune system works.
Question
What are the two main branches of the immune system?
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Answer
Innate immunity (fast, non-specific, first line of defence) and adaptive immunity (slower, antigen-specific, develops immunological memory).
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Question
What are the physical and chemical barriers of the innate immune system?
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Answer
Skin (physical barrier), mucus (traps pathogens), cilia (sweep pathogens out), stomach acid (kills ingested pathogens), and antimicrobial peptides in secretions.
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Question
What are phagocytes and name two types?
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Answer
Cells that engulf and destroy pathogens by phagocytosis. Key types: neutrophils (first responders) and macrophages (long-lived, also present antigens).
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Question
What is the inflammatory response?
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Answer
A local innate response to infection or injury: vasodilation increases blood flow (redness, heat), increased permeability brings immune cells to the site (swelling), and chemical signals (cytokines) recruit phagocytes (pain).
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Question
What is an antigen?
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Answer
Any molecule (usually on a pathogen's surface) that can be recognised by the adaptive immune system and trigger an immune response.
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Question
What is an antibody (immunoglobulin)?
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Answer
A Y-shaped protein produced by B cells (plasma cells) that binds specifically to an antigen — neutralising pathogens, marking them for destruction (opsonisation), or activating complement.
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Question
What is the difference between B cells and T cells?
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Answer
B cells produce antibodies (humoral immunity). T cells either kill infected cells directly (cytotoxic T cells) or regulate immune responses (helper T cells).
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Question
What is the role of helper T cells (CD4+)?
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Answer
They activate B cells to produce antibodies, stimulate cytotoxic T cells, and recruit other immune cells — via cytokine signalling. They are the primary target of HIV.
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Question
What is the role of cytotoxic T cells (CD8+)?
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Answer
They kill cells infected by viruses or intracellular pathogens by inducing apoptosis — via perforin and granzymes. They recognise antigens presented on MHC class I molecules.
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Question
What is MHC (Major Histocompatibility Complex)?
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Answer
Cell surface proteins that present antigen fragments to T cells. MHC class I is on all nucleated cells (recognised by CD8+ T cells). MHC class II is on antigen-presenting cells (recognised by CD4+ T cells).
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