Monoclonal Antibodies

Monoclonal antibodies (mAbs)

Antibodies that are clones from one parent cell, specific to one type of antigen.

• ability to bind to only one protein antigen → target chemicals and cells in the body

Production of monoclonal antibodies

1. Specific antigen injected into an animal (e.g. mouse)

2. Mice lymphocytes producing complementary antibodies extracted

3. Lymphocytes fused with myeloma cells (tumour cells → divide rapidly) to form hybridoma cells

4. Hybridoma cells divide to produce clones of itself → produce same antibody

5. Monoclonal antibodies collected and purified.

Uses of monoclonal antibodies

• Detection of pathogens

• Location of cancer cells and blood clots

• Used in pregnancy test kits

Myeloma cells

Type of tumour cell.

Uses of monoclonal antibodies - Pregnancy kit tests

Used to detect a hormone, hCG, in the urine of pregnant women

How pregnancy test works

There are two sections of the stick:

→ first section: mobile mAbs complemetary to hCG hormone - attached to blue beads

→ second section: stationary mAbs which are stuck to the stick

1. Individual urinates on first section: If hCG present, it binds to mobile mAbs attached to blue beads to form hCG / antibody complexes

2. Carried in the flow of liquid to second section

3. Stationary mAbs bind to hCG / antibody complexes

4. As each are bound to a blue bead, results shown as blue line → indicating pregnancy

Pregnancy test results if pregnant - simple

• hCG in urine binds to mAbs attached to a blue bead

• mAbs with hCG diffuse up the stick

• mAbs fixed to the stick bind to hCG

• Blue line forms

Pregnancy test results if not pregnant

No hCG in urine so a blue line is not formed.

Uses of monoclonal antibodies - Measure and monitor

Used to measure and monitor levels of hormones or chemicals in the blood.

• mAbs modified to bind to molecule wanted

• mAbs bound to fluorescent dye

• if molecules present, the mAbs bind to it, and dye can be observed

E.g. Blood screening for HIV infections

Uses of monoclonal antibodies - Cancer treament

1. Producing mAbs that bind to tumour markers to stimulate immune system to attack that cell.

2. Using mAbs to bind to receptor sites on cell membrane of cancer cells → growth-stimulating molecules cannot bind → stops cell divison

3. Using mAbs to transport toxic drugs, chemicals or radioactive substances → only damage cancer cells

Advantages of monoclonal antibodies

• Specific to one particular antigen - healthy cells not affected

• Can treat many different conditions

Disadvantages of mAbs

• Difficult too attach mAbs to drugs

• expensive to develop

• produced from mice lymphocytes - trigger immune response in humans