Lecture 43: Elements of the Adaptive Immune Response

Question 1

MHC = ?

Answer 1

• Major Histocompatibility Complex

Question 2

Leukocytes are a minor constituent of blood but are the ____ cells involved in ____.

Answer 2

• Main

- Immunity

Question 3

You cut yourself with a bread knife this morning, your immune system then works hard to destroy invaders. Picks up all the pieces of the invaders and sends them to the lymph nodes. These are done by the ______ cells, the most potent antigen presenting cell. In the lymph nodes there is __ cell and __ cell activations. This makes antibodies and _____ T Cells.

Answer 3

• Dendritic
• T + B
• Cytotoxic

Question 4

The dendritic cell is a member of the ___ club and interactions with other cells cause the plasma cell to produce antibodies. Another interaction causes cell apoptosis (cell suicide).

Answer 4

• APC (antigen presenting cells)

Question 5

What is ‘Antigen’?

Answer 5

• Anything that has the potential to be recognised by the immune system
• Foreign antigen (transplants, pathogens, some chemicals). Anything from ‘outside’. e.g pollen.
• Auto-antigen: Immune system normally tolerant of auto (self) antigen. May be recognised in autoimmune disorders. (Type I Diabetes, Rheumatoid Arthritis)

Question 6

Purpose of antigen uptake:

Answer 6

• Clearance of pathogens (innate response)

- For presentation to T Cells (adaptive response)

Question 7

What encourages other cells to respond to infection?

Answer 7

• Peptides loaded onto MHC molecules for immune surveillance
• Presents fragment of antigen on MHC molecules (in the form of peptides)
• Know that it’s bad if the sequence is different to ones found in the body

Question 8

Where is MHC present? What’s the difference between the two MHC types?

Answer 8

• MHC-I presents intracellular antigen. Antigens produced inside the cell. Expressed on all nucleated cells.
• MHC-II presents extracellular antigen. Expressed only on antigen presenting cells.

Question 9

Describe the MHC structure:

Answer 9

• Peptide-binding cleft (peptide usually held there by weak electrostatic forces for a few hours or days)
• 4 proteins, 1 is embedded in membrane

Question 10

What do T Cells do to those with MHC on them?

Answer 10

• Inspect and decide whether to take action

Question 11

MHC-I antigen processing:

Answer 11

• Antigenic proteins are degraded to peptides in cytoplasm
• Peptides are imported into endoplasmic reticulum
• Peptide loading takes place in the ER

Question 12

Phagocytosis occurs with MHC-__ molecules.

Answer 12

• II
• Phagolysosome sent to cell membrane (MHC waving around for T-Cells to view)
• Destruction of exogenous pathogen in acidic phagolysosome
• Peptide loading of MHC-II takes place in phagolysosome.

Question 13

Summary:

Answer 13

• Subsets of WBC’s mediate the immune response
• Antigen (self or foreign) is anything that an immune system recognises
• Peptides are fragments of protein antigen that are displayed by MHC-I and MHC-II on cells
• Endogenous antigens = MHC-I
• Exogenous antigens = MHC-II