Overview of immunology

Question 1

Which cell do immune cells arise from?

Answer 1

pluripotent hematopoietic stem cell

Question 2

State the cells in the myeloid lineage and their functions

Answer 2

Neutrophils- phagocytosis
Eosinophil- helminth(parasitic) infections
Monocyte/macrophage- phagocytosis, antigen presentation
Dendritic cell- antigen presentation
Basophil- helminth infections

Question 3

State the cells in the lymphoid lineage and their functions

Answer 3

B cells- make AB’s, antigen presentation
T cells- CD4 support other immunological components, CD8 kill infected cells

**both form part of adaptive immunity

NK cell (Innate)- direct lysis of infected cells and AB-dependent cellular cytotoxity

Question 4

State the different signalling pathways

Answer 4

It occurs via soluble mediators = intercellular

• Endocrine (distant)
• Paracrine (near)
• Autocrine (self)
• Juxtacrine (contact mediated)

Question 5

What is the difference between cytokines and chemokines?

Answer 5

Cytokines- small proteins released by cells that have an effect on another cell. Important in communication between immune cells and tissues

Chemokines- different structure, receptors and nomenclature. Main role - temporal and spatial organisation of cells and tissues

Question 6

Describe innate antigen receptors

Include recognition, advantages and disadvantages

Answer 6

• dont recognise specific antigens, instead pattern recognition receptors (PRRs) which recognise PAMPs
• genome encoded
• not clonally distributed e.g. Mannose binding ligand (MBL) bind with high affinity to mannose and fructose residues with correct spacing
• work quickly
• unable to ‘learn’ as germline encoded and therefore cant be changed

Question 7

Describe adaptive antigen receptors

Include recognition, advantages and disadvantages

Answer 7

• recognise antigens specifically via T/B cell receptors
• produced by random somatic recombination events between gene segments –> huge receptor diversity
• clonally distributed
• permit specificity and memory in immaturity

Question 8

Describe the structure and function of B cells

Answer 8

• Constant region= 2x heavy chain
• variable region (antigen binding site) made from 2x light chains

The receptor (antibody) may be surface bound or secreted and is able to recognise intact antigens

Question 9

Describe the structure and function of T cells

consider drawing it out

Answer 9

Both variable and constant region made from alpha and beta chain associated to carbohydrate. Hinge crosses transmembrane region becoming cytoplasmic tail. Connected by disulphide bond

• Only surface receptor on CD4 via MHC2 or CD8 via MHC1.
• Recognise processed antigen in the form of linear peptides

Question 10

When are the most useful adaptive immune cell receptors selected? Consequences?

Answer 10

After birth upon exposure to pathogens

–> antigen processing pathways –> clonal selection –> memory

Question 11

What are effector mechanisms and give three examples?

Answer 11

Shared between innate and adaptive

• barriers (skin, acidic gut)
• cytokines
• complement
• phagocytosis (increased by opsonisation)
• cytotoxicity
• antibody-dependent cellular cytotoxicity
• mast cell and eosinophil degranulation

Question 12

How do CD8 T cells work?

Answer 12

• Virus infects cells and synthesises viral proteins in cytosol
• Peptide fragments of viral proteins bound by MHC1 in ER
• Bound peptides transported by MHC1 to cell surface
• Cytotoxic T cell recognise virally infected cel expressing correct peptide in MHC1

Question 13

Consider acute inflammation

What are the cardinal features?
Which blood vessel changes underline the process?

Answer 13

• Heat, pain, redness, swollen
• Vasodilation, adhesion molecules, increased permeability
• Clinical features are therefore defines by an interaction between the pathogen and host immunity