Immunology

• We have specific and a non-specific response sytems

• Non-Specific = barriers, like skin and mucus, HCl in the stomach, and phagocytosis.

• Specific = Immune system and antibodies

Phagocytosis – using Lytic Enzymes (hydrolysis)

Absorption

Role of Histamine

• Histamine is a hormone which is released at a damaged site

• Inflammation causes dilation of blood vessels

• More phagocytes are delivered to the damaged area.

The Specific Response

• Slower than the Non-Specific• Longer lasting• Responds to ANTIGENS

- Proteins/Glycoproteins (see cell membrane notes) on the cell surface membrane which trigger an immune response.

• Utilises white blood cells-LYMPHOCYTES (B and T Lymphocytes)

B Lymphocytes – from stem cells in bone marrow

T Lymphocytes

Made in the Thymus Gland.

Two types of Specific Immunity

• Cell-Mediated Response (uses T Lymphocytes)

• Humoral Response (uses B Lymphocytes)

Cell Mediated Response.

• This is a response that occurs when our cells have been infected – e.g. by a virus

• Infected cells (and macrophages) display the foreign antigens on their cell surface membrane

• One of our many T-helper cells will be complementary to these antigens

The T-helper cells stimulate the cloning of cytotoxic T cells

Complementary shapes Antigen of pathogen

Chemicals are released which cause MITOSIS of the correct cytotoxic T cells

Mitosis of T cells

Stimulated by the T-helper cells

Cloning of Killer T cells

How T cells protect us

• They kill infected cells by producing a protein which destroys the cell membrane

• They stimulate Phagocytes

• They stimulate B cells to divide

• They form T memory cells

Cell-Mediated Immunity

YouTube - Cell Mediated Immune Response

The Humoral Response

• This process involves B Lymphocytes and the production of antibodies

• It begins in the same way as the cell-mediated response.

Complementary shapes

Antigen of pathogen

Chemicals are released which cause MITOSIS of the correct cytotoxic T cells

AND B CELLS

B Cell cloning occurs by mitosis

B Cell

Antigen of pathogen

Cytokines released by T helper cells

This cell could be a B cell or a macrophage

B Cells

• Cloned B Cells can form PLASMA CELLS or MEMORY CELLS

• Plasma Cells – produce Antibodies

Antigen presenting by B cell or macrophage

Cloning/Mitosis

Complementary B cell

Produces antibodies

Complementary T-helper cells will release chemicals to stimulate mitosis

B Memory Cells• Stay in our tissues for many years.

• They carry out mitosis immediately upon contact with the complementary antigen

• A very quick, secondary response

• We do not become ill

• The same process with T memory cells

So, how do vaccines work?

Humoral Response

• YouTube - Antibody Mediated Immune Response

Summary of both types of Immunity

• YouTube - Review of Antibody and Cell-mediated Immunity

Antibodies

Definition of antibody

• An immunoglobulin protein that is produced by B plasma cells in response to non-self antigens.

The Antigen-Antibody Complex

• The antibodies attach to the antigen on the pathogen and destroy it.

MUST be a Complementary variable

region!

Funny animation link

• YouTube - Immune System Animation

Why do we get flu more than once?

• Antigenic Variability!

• Some antigens constantly change (mutation)

• Memory cells are no longer complementary

• The Primary Response is initiated instead of the secondary response.

Pathogens have many antigens

• So we produce many different types of antibody – POLYCLONAL antibodies

• Scientists can clone antibodies in the laboratory

• They can clone just one kind at a time

• These are MONOCLONAL antibodies

Monoclonal Antibodies

• These antibodies are complementary to a specific protein.

• Can be used to mark and identify proteins in blood or urine

• E.g. in Pregnancy tests, or drug tests in athletes

Uses in cancer treatment

• Cancer cells will present antigens on their surface membrane

• Specific monoclonal antibodies will attach to these cells and can activate a cytotoxic drug to kill the cell.

Uses in Transplant Surgery

• Transplanted organs often suffer rejection from the action of our T Cells

• Monoclonal antibodies can attach to and “knock out” these T Cells.

Other use

• The monoclonal antibody can be used to label and separate a chemical in a mixture.

• Read pages 110-111 and discuss the ethical issues associated with monoclonal antibodies, and how society uses scientific knowledge to inform decision-making.

Vaccines• You should now understand how

vaccines work.

But what makes a successful vaccine?

A Successful Vaccination Programme

• Must be economically viable to produce enough for a vulnerable population

• Have few side-effects

• Easy to store and transport

• Trained staff must be available

• It must be possible to carry out HERD IMMUNITY i.e. to immunise a total population

Evaluating vaccines

• They may not eliminate a disease because...

- Individuals may have a poor immune system

- Disease may spread BEFORE the vaccine has produced the required memory cells

- The pathogen could mutate

- There may be too many antigens on the pathogen (e.g. cold virus / HIV)

- People may object –e.g Religion, MMR

Cholera and TB Vaccine Evaluation• Cholera has high antigenic variability

• Populations are now more mobile so diseases spread much more easily

• HIV cases have risen so more people get TB

• Poverty and wars create overcrowded conditions so TB cases have risen

• More elderly people so more TB.

Now complete the Application questions!