The immune system in action

Question 1

What is a brief overview of the immune response during a course of infection?

Answer 1

1. local infection penetrating the epithelium. Phagocytes, complement, AMPs destroy invading microorganisms.
2. local infection of tissues. complement activation, dendritic cells migrate to lymph nodes, phagocytes, NK cells, cyto and chemokines.
3. lymphatic spread. pathogens trapped and phagocytosed in lymphoid tissue, adaptive immunity initiated by migrating dendritic cells.
4. adaptive immunity. infection cleared by specific antibodies, T cell dependent macrophage activation and cytotoxic T cells.

Question 2

What is the first Ig to be produced in the immune response?

Answer 2

IgM, which is then switched to IgG.

Question 3

What does the IgM initiate?

Answer 3

The classical pathway.

Question 4

What pathogen induces exotoxin production and what’s the effect?

Answer 4

Streptococcus pyogenes - associated with scarlet fever.

Question 5

What does it mean by indirect mechanisms of damage by pathogens?

Answer 5

This refers to the immune system damaging the host due to the pathogen.

Question 6

What pathogen induces endotoxin production and what’s the effect?

Answer 6

Salmonella and E.coli which can cause meningitis and pneumonia.

Question 7

What pathogen induces a direct cytopathic effect and what’s the effect?

Answer 7

Influenza virus which can cause hepatitis and shingles and cold sores.

Question 8

What are immune complexes and what are their cause?

Answer 8

Antibodies bind to a particular Ag, forming a big mass that can cause problems such as kidney damage or disease. This can happen during HPB, streptococcus pyogenes and malaria.

Question 9

What are anti-host antibodies and what are their cause?

Answer 9

This is where antibodies are produced against our own cells, again can be caused by streptococcus pyogenes and can result in rheumatic fever.

Question 10

What is cell-mediated damage?

Answer 10

Cytotoxic T cells go around killing our own cells, this is required by the immune system, but in this case is uncontrolled.

Question 11

Examples of immune response: Infectious agent (leprosy):

Answer 11

• caused by mycobacterium lepra (intracellular bacteria).
• it causes skin lesions
  There are 2 types:
  Tuberculoid and lepromatous.
  With TL, people tend to live and with LL, they die.
  In TL, cytokines present are from the type 1 immune response, caused by Th1 cells activating macrophages causing intracellular killing. With LL, it is the Th2 response which activates antibodies IgE. IgE defends our bodies against extracellular pathogens, so the defence will not work.

Question 12

Examples of immune response: Immunodeficiency:

Answer 12

This is when the ability to fight infection is decreased. It can be primary (born with) which is rare but causes severe immunodeficiency where there are no T or B cells. Or secondary (weakened by infection) which can be caused by stress, malnutrition, infection and immunosuppressive or cytotoxic drugs. Secondary can lead to certain cancers e.g. some people with HIV develop HHV8 which causes kaposi’s sarcoma.

Question 13

Examples of immune response: Immunopathology:

Answer 13

This is when our immune system us too enhanced and causes excessive and ineffective damage to the host. This occurs in an infection to allergies and autoimmune diseases.

Question 14

Examples of immune response: Hypersensitivity:

Answer 14

There are 2 types - allergies and autoimmunity.
This means the immune system is over sensitive.

Question 15

Type 1 hypersensitivity - IgE and allergies:

Answer 15

This is where histamine is unnecessarily released from mast cells due to the binding of IgE with an assumed pathogen, such as pollen.
Histamine causes vasodilation, and an opportunity for many immune cells to access the site of ‘infection’ - but they do not need to be there.

Question 16

Type 2 hypersensitivity: IgG and IgM mediated destruction

Answer 16

Erythroblastosis fetalis.
The mother has the rhesus - antigen blood type, however the foetus has the rhesus + factor. Some of the rhesus particles move into the mother, the immune system views it as foreign and creates an adaptive response against it. the next time the mother is pregnant and the babies rhesus + moves over, her immune system will attack it through IgG (can cross placental wall) which will attack the babies RBCs and the baby will have severe anaemia.

Question 17

Type 3 hypersensitivity: Auto-antibodies:

Answer 17

Systemic lupus erythematosus (SLE). Our body produces auto-antibodies against our selves (DNA) and these immune complexes are deposited at susceptible sites which can cause a rash on the face for example. or arthritis.

Question 18

Type 4 hypersensitivity: Type 1 diabetes:

Answer 18

This is an autoimmune disease where the immune response is attacking insulin producing beta cells in the pancreas due to over reactive T cells. Cytotoxic (CD8) T cells apoptose beta cells, reducing insulin production and increasing blood glucose levels.

Question 19

What is the cause of autoimmune diseases?

Answer 19

mostly were unsure.
- loss of self-tolerance
- increased in females in terms of the sex hormones and western cultures.

Question 20

How can we activate the immune defence through vaccines?

Answer 20

The immune system recognises and self-destroys cells that have become altered and could become tumours. Tumour specific antigens can provide a target for vaccination and other forms of immunotherapy.
The injection of a BCG (TB) vaccine into the bladder tumour can lead to the immune killing of tumour cells - the TB vaccine has nothing to do with cancerous tumours. The TB vaccine enhances the CD4 T cell response.

Question 21

what is examples of Immunotherapy?

Answer 21

Immunotherapy can either -
Enhance our immune response:
Portion of our blood can be taken and T cells are extracted, we see which ones are really successful and in the lab we enhance them and then put them back into the body. This causes them to have a more potent effect and recruit other T cells with a now enhanced effect also.
Release immune system blocks caused by the tumour:
monoclonal antibodies target areas such as tumours by binding to them and signalling to other cells to attack it, they can also be used to target a particular system in the tumour and block it so it can no longer switch of CD4 T cells.

Question 22

What are monoclonal antibodies?

Answer 22

Help to fight against some of our own immune responses that are doing too much.
Rheumatoid arthritis is swelling of joints, particularly the knuckles, caused by inflammation from the body attacking itself. TNF alpha is the pro-inflammatory cytokine involved in RA. Anti-TNF alpha therapy reduces the response of the TNA alpha causing reduced swelling and loss of pain.