Immune System

Question 1

Describe the external features of the innate immune system

Answer 1

Skin - acts as a physical barrier
Mucus membranes - line surfaces that are externally exposed
Enzymes that attack bacteria in the saliva

Question 2

Describe the internal features of the innate immune system

Answer 2

Fever, swelling, pain all caused by phagocytes:

Neutrophils are the first thing attracted to an infectious agent
Macrophages come from monocytes and the engulf and digest pathogens
Natural Killer Cells - travel in blood and lymph, recognise infected cells by the lack of usual MHC presenting on cell surface, triggers apoptosis

Question 3

Which cells trigger the inflammatory response?

Answer 3

Mast cells, which send out histamines

Macrophages

Question 4

Describe the symptoms that arise in the inflammatory response and how these fight pathogens

Answer 4

Increase in temperature caused by macrophages releasing pyrogens to trigger the hypothalamus
Also causes body to withhold iron and zinc, preventing bacterial growth.
Increase in blood vessel permeability, causing swelling and for the excess fluid to be drained away and cleaned by the lymphatic system. Triggers clotting and attracts phagocytes via cytokines.

Question 5

Describe the function of the adaptive immune system

Answer 5

The adaptive immune system is a systemic (whole body) defence, which has to be introduced to a pathogen and recognise that it’s a threat

Question 6

What are the two types of adaptive immunity

Answer 6

Humoral and cell mediated

Question 7

What do b lymphocytes carry on their surface

Answer 7

Thousands of membrane bound antibodies each unique to that particular b lymphocyte, each individual one specific to an antigen. Millions of antibodies present in the b lymphocyte population. High odds of matching a pathogen

Question 8

Where are b lymphocytes produced and matured?

Answer 8

Bone marrow

Question 9

When a b lymphocyte finds an antigen that it carries the matching antibody for what happens?

Answer 9

It binds to the antigen and summons the humoral immune response. The b-cell clones itself.

Question 10

What two types of b lymphocyte do they clone themselves into in the humoral immune response

Answer 10

Effector cells and memory cells

Question 11

Effector b lymphocytes have an increased amount of RER. Why?

Answer 11

Increased peptide production rate, therefore increased rate of production of antibodies

Question 12

Describe how the effector B cell antibodies neutralise the antigens?

Answer 12

They block the binding site on viral and bacterial toxins so they cannot bind and infect healthy tissues

Question 13

What is agglutination?

Answer 13

When the effector B cells bind multiple antigens at once and make a cluster of them, making it harder for them to travel around the body, and targeting them for destruction by macrophages, innate immune phagocytes and specialised leukocytes

Question 14

How is active humoral immunity gained?

Answer 14

Naturally, via experiencing and encountering an antigen

Artificially, via vaccination

Question 15

Passive humoral immunity is gained how?

Answer 15

Passive immunity it the transfer of pre synthesised antibodies, it doesn’t require them to be synthesised in response to exposure.

Babies gain passive immunity from their mother in utero and via breast milk.

Immunity can be gained by serums made from the blood plasma of an immune donor.

These don’t last as long as active immunity

Question 16

Cell mediated immunity is defence using what sort of lymphocytes, and where are they synthesised?

Answer 16

T lymphocytes, produced in the thymus. They defend cells that are infected

Question 17

All cells carry major histocompatability complexes, what are these?

Answer 17

MHCs bind to fragments of endogenous protein presented on the surface of cells

Question 18

How do MHCs allow T cells to target foreign cells

Answer 18

MHCs bind fragments of exogenous antigen. When a phagocyte engulfs an antigen, it presents proteins on the surface of the cell, via MHCs. T cells identify cells to attack by the presence of fragments of antigen, as they can’t recognise whole antigens.

Question 19

Which class of MHCs bind which type of T cell

Answer 19

Class I MHCs bind cytotoxic T cells

Class II MHCs bind helper T cells

Question 20

What are the types of T cell

Answer 20

Helper T cells:

1) Effector
2) Regulatory
3) Memory

Cytotoxic T cells

Question 21

What is the role of cytotoxic T cells in cell mediated adaptive immunity

Answer 21

They roam the blood and lymph recognising cells presenting antigen fragments on class I MHCs and signalling apoptosis

Question 22

How do T helper cells help mature B effector cells

Answer 22

B cells engulf any pathogen it matches to as an antigen. The B cell presents the antigen fragments on its surface. It then stops and waits for the T helper cell to bind and recognise the presented antigen, and trigger the full B cell, humoral mediated response by releasing cytokines

It acts as a safeguarding hyperactive immune system, and gives us self tolerance to our own tissues

Question 23

Name some diseases that happen when self tolerance goes wrong and the immune system attacks the body cells

Answer 23

Diabetes type I

Multiple sclerosis

Question 24

What is the role of a regulatory T cell?

Answer 24

A regulatory T cell releases inhibitory cytokines to signal to other immune cells to stop attacking once the pathogen is eliminated.