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Module 7: Infectious Disease
Quick questions on Adaptive immune response, humoral and cell-mediated immunity: HSC Biology Module 7
15short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is antigens and antigen presentation?Show answer
An antigen is any molecule (usually a protein or polysaccharide) that triggers an adaptive immune response. Antigen-presenting cells (APCs) including macrophages and dendritic cells engulf pathogens, digest them, and display fragments on MHC class II molecules. Infected cells display intracellular antigen fragments on MHC class I.
What is lymphocyte types?Show answer
All lymphocytes mature into one of three classes.
What is humoral immunity (B cells and antibodies)?Show answer
Targets pathogens in body fluids.
What is cell-mediated immunity (T cells)?Show answer
Targets infected, cancerous or abnormal host cells.
What is primary and secondary responses?Show answer
Primary response. First exposure to a pathogen. Takes 5 to 14 days to produce significant antibody. Symptoms may develop while immunity is building.
What is b lymphocytes?Show answer
Mature in the bone marrow. Each B cell has a unique surface antibody (B-cell receptor) that recognises one antigen.
What is t lymphocytes?Show answer
Mature in the thymus. Each T cell has a unique T-cell receptor (TCR) that recognises one antigen displayed on MHC. Two main subtypes: - Helper T cells (CD4) recognise antigen on MHC class II.
What is memory cells?Show answer
A subset of activated B and T cells become long-lived memory cells.
What is antibodies?Show answer
Y-shaped proteins with two antigen-binding sites. Functions: - Neutralisation. Bind viruses or toxins, blocking their attachment to host cells. - Agglutination. Clump pathogens together, easing phagocytosis.
What is primary response?Show answer
First exposure to a pathogen. Takes 5 to 14 days to produce significant antibody. Symptoms may develop while immunity is building.
What is secondary response?Show answer
Re-exposure to the same pathogen. Memory cells recognise the antigen within hours. Antibody production is faster, higher and longer-lasting.
What is at vaccination?Show answer
Attenuated measles antigens are processed by APCs. Helper T cells and B cells specific for measles are activated. After 1 to 2 weeks, IgG antibodies are produced and memory B and T cells form.
What is on re-exposure?Show answer
Within 1 to 2 days, memory B cells differentiate into plasma cells, producing large amounts of IgG. Memory cytotoxic T cells destroy infected cells. The virus is cleared before significant disease develops.
What is confusing B and T cells?Show answer
B cells produce antibodies. T cells kill infected cells (cytotoxic) or coordinate the response (helper).
What is forgetting MHC?Show answer
T cells cannot recognise free antigen. They only recognise antigen presented on MHC molecules.