6. ETA Section 1-3

Question 1

What are three types of phagocytes involved in innate immunity ?

Answer 1

Neutrophils, Macrophage, Dendritic Cells

Question 2

How do B lymphocytes respond when antigen enters body?

Answer 2

1. B cells with receptors complementary to antigen are stimulated to divide by mitosis CLONAL SELECTION
2. The clone of cells divide CLONAL EXPANSION
3. Some B cells differentiate and form plasma cells which produce monoclonal antibodies (all antibodies produced by 1 plasma cell have same antigen specificity)
4. Some B cells differentiate form memory cells which remain in circulation for Long time

Question 3

Characteristics of Adaptive immune system

Answer 3

1. Specificity and diversity
   Ability to distinguish between many diff antigen
   Lymphocyte repertoire very diverse
2. Clonal selection and expansion
   Undergo proliferation when activated by antigen
   Generate thousand of clonal progeny cells with same antigen specificity
   A few antigen-specific lymphocytes can keep pace with rapidly proliferating pathogen
3. Immunological memory
   Immune response mount larger, rapid and more effective response to repeated exposure to same antigen
   Long-term protection against prior infection

Question 4

Steps of adaptive immune system TDAABS

Answer 4

Threat - antigen evades first two lines of defence and enters body

Detection - macrophage encounters, engulfs through phagocytosis

Alert - macrophage alert helper T cell by presenting peptide antigen fragments via MHC (macrophage must find the Th cell with receptor specific to antigen, likely in lymph node)

Alarm - activated T helper secrete cytokines, activate antibody production and cytotoxic T cell
Helper T also bind to B cell and promote differentiation into plasma and memory cells

Building specific defences - appropriate naive B or T cell activated, divide rapidly [clonal selection]

Defence through antibody-mediated response:
Activated B cells divide, produce effector cells (plasma cells) that secrete antibodies into bloodstream
Antibodies do:
Neutralisation- antibodies bind to proteins on surface of virus prevent infection of host cell

Opsonization- antibodies bound to antigens present a readily recognised structure to promote phagocytosis, or can link the pathogen cells into aggregates

Complement system- work tgt with proteins, binding of complement protein form pore in membrane of cell, cell swell and lyse

Defence through cell-mediated response: 
Cytotoxic T cells attack and destory cells that display MHC class I-antigen complex 

Surveillance

Question 5

Compare primary immune response to secondary immune response

Answer 5

PRIMARY: small magnitude, slow kinetics as mediated by naive lymphocyte that are encountering antigen for first time
SECONDARY: subsequent encounter with same antigen, activation of memory B and T cells, response more rapid and larger
Each encounter with microbe generates more memory cells -> long lasting protection