Introduction to the adaptive immune system

Question 1

a) extracellular adaptive responses
b) intracellular adaptive responses

Answer 1

a) Extracellular interstitial spaces, blood and lymph - antibodies
Extracellular epithelial surfaces - antibodies
b) Intracellular cytoplasmic - cytotoxic T cells
Intracellular vesicular - T cell activation of macrophages

Question 2

B lymphocyte overview of functions

Answer 2

Recognise simple chemicals, sugars, small peptides, large protein complexes such as viruses. Recognise molecules in their native conformation. Generated in the bone marrow where BCR genes rearrange to produce millions of clones with diverse specificity. Differentiate into plasma cells which secrete antibody or immunoglobulin (a soluble version of the BCR)

Question 3

Antibodies and antigens overview and graph of antibody response after 1st and 2nd exposure

Answer 3

Antibodies have specific recognition sites capable of binding antigen. An antigen is defined as anything that can be bound by an antibody (or T cell). Antibodies have variable regions that interact with the antigen and constant regions that recruit effector functions. Constant regions can be recognised by Fc receptors on cells such as macrophages, neutrophils, basophils and mast cells and can interact with complement. Antibodies interact with antigenic determinants or epitopes (where the antibody binds), which can be linear or conformational
Antibody responses take time but are more powerful and occur more rapidly upon a second exposurew to the antigen

Question 4

Ways antibodies work (3)

Answer 4

1) neutralisation of toxin
2) opsonisation - they coat the antigen on the pathogen, then the Fc regions binds to receptor on a macrophage to be phagocytosed
3) complement activation

Question 5

What are the two major classes of T cell and how are they defined

Answer 5

CD4: T helper cell. MHC class II. Function is cytokine production, help for B cells and cytotoxic T cells
CD8: Cytotoxic T cell. MHC class I. Function is cytokine production and cytotoxic lysis of infected cells

Question 6

MHC class I vs MHC class II

Answer 6

MHCI - survery the internal cell environment. Presents peptides from proteins made inside the cell (eg virus). Signals to CD8
MHCII - survey the external cell environement. Presents peptides from external protein antigent hat enters the cell. Signals to CD4

Question 7

Lymphocyte derivation

Answer 7

From stem cells in the bone marrow

Question 8

a) the role of the lymphatic system
b) general structure of a lymph node

Answer 8

a) facilitates interaction between T cells, B cells and APCs. Naive T and B cells patrol through the peripheral lymphoid organs ready to respond to an antigen.
b) (see image)