monoclonal antibodies

what are monoclonal antibodies

Antibodies produced from a single group of genetically identical B-cells (plasma cells)

features of monoclonal antibodies

- all identical in structure

- very specific as have unique tertiary structure

- can be used to bind to anything that is complementary to the antigen binding site

what can monoclonal antibodies be used for

-Pregnancy tests (to bind to HCG found in urine)

-To measure levels of hormones

-To treat some diseases (deliver a substance to a specific part of the body)

what is humanisation

Modification of monoclonal antibodies from mouse-tissue to make them more human-like before use on humans

monoclonal antibodies used in targeted medication

two types

direct monoclonal antibody therapy

indirect monoclonal antibody therapy

Direct monoclonal antibody therapy

- monoclonal antibodies produced are specific to antigen on cancer cells

- when given to patients they attach onto receptors on cancer cells

- blocks chemicals signals that stimulate their uncontrolled growth

- not toxic and highly specific so less side effects

Indirect monoclonal antibody therapy

Monoclonal antibodies with drugs attached to target and destroy cancer cells directly

reduces harmful side effects traditional chemo/radiotherapy can produce

ELISA test

enzyme-linked immunosorbent assay

what happens in an ELISA test

-enzyme attached to antibodies

- when this enzyme reacts with a certain substrate, a coloured product is formed

- colour change = antigen/antibody of interest is present in sample being tested

What is a direct ELISA test?

uses a single antibody that is complementary to the antigen being tested for

What is an indirect ELISA test?

two different antibodies (primary and secondary)

How does an indirect ELISA test for HIV work?

HIV antigens fixed to bottom of test well

Patient's blood plasma added

If HIV antibodies present → bind to antigen.

Well is washed to remove unbound antibodies.

Add secondary antibody with attached enzyme.

This antibody binds to the patient's HIV antibodies.

Wash again to remove unbound secondary antibodies.

Add colourless substrate.

If enzyme present → substrate converted to coloured product.

Colour change = positive result

why is washing important in the ELISA test

Removes unbound antibodies

Prevents false positives

Ensures colour only appears if binding occurred

ethical issues with monoclonal antibodies

1) involves the use of mice to produce antibodies and tumour cells (purposely inducing cancer into mice)

2) in March 2006, drug testing for monoclonal antibodies sent patients into multiple organ failure, raising issues

Monoclonal antibodies in cancer treatment (6 marks)

• MABs have binding sites complementary to cancer cell antigens

• Bind specifically to cancer cells

• Attached to drugs/toxins/radioactive substances

• Deliver these directly to cancer cells- kills cell

• Or no drugs, block receptors instead- prevent cell division

• Or mark cells for immune destruction

• Targeted so less damage to healthy cells

Monoclonal antibodies in pregnancy tests (6 marks)

• used to detect hCG hormone in urine

• Mobile antibodies with dye bind to hCG

• Form antigen-antibody complex

• Complex moves along strip test to line, line has immobilised antibodies

• Second binding- coloured line forms

• Control line bonds to mobile antibodies regardless if hCG present to confirm test working properly