This document provides an overview of the Enzyme-Linked Immunosorbent Assay (ELISA) technique. It discusses the principle behind ELISA, which involves using an enzyme-linked antibody to detect antigens or antibodies. The general procedure of ELISA is outlined in 3 steps: coating the wells with antibodies, adding and washing away unbound sample, and detecting antigen-antibody interactions using enzyme-linked antibodies and a color-changing substrate. The types of ELISA - indirect, sandwich, and competitive - are also briefly described. Finally, the advantages of ELISA being inexpensive, specific, and sensitive are contrasted with potential disadvantages like complex enzyme measurements and false positives.

1. HEMCHAND YADAW
UNIVERSITY,
DURG
ENZYME LINKED
IMMUNOSORBENT ESSAY
(ELISA)
PRESENTED BY:
DHAMESHWAR SAHU
M.Sc. 1STsemester

2. INTRODUCTION
ELISA is a qualitative or quantitative immunological
procedures in which the Ag-Ab reaction is monitored by
enzyme measurements.
The term ELISA was first used by Engvall & Perlma in
1971.
The ELISA test was the first screening test commonly
employed for HIV. It has a high sensitivity.

3. Principle
Its principle is similar to RIA but depends on an enzyme
rather than a radioactive label.
An enzyme conjugated with an antibody reacts with a
colorless substrate to generate a colored reaction
product. Such a substrate is called a chromogenic
substrate.
A number of enzymes have been employed for ELISA
including alkaline phosphatase, horseradish peroxidase
and β-galactosidase.

4. Equipment's
Microwell
plate
It is flat bottom polystyrene plate containing 8 x 12 wells holding 350 µl
each.

5. Equipment's
Multi-
pipette
It is an 8-channel 100 μL pipette which is a good help for even small scale
work.

6. Equipment's
Washing
device
It is a manually operated washing
device.

7. Equipment's
Microplate
washer
These are very efficient with very low carry over contamination.

8. General Procedure of ELISA
The wells are coated with antibodies.
Sample is added which may contain antigen.
Removal of unbound antigens by washing.
Addition of another antibody which is linked with enzyme.
Interaction of enzyme with particular substrate.
This interaction produces color through which we can observe
a particular antigen (disease).
The antigen-antibody interaction took place.

9. Types of ELISA
Competitive ELISA
There are three types of ELISA :-
. Indirect ELISA
Sandwich
ELISA

10. Types of ELISA
Indirect
ELISA

11. Types of ELISA
Sandwich ELISA

12. Types of ELISA
Competitive ELISA

13. Advantages of ELISA
Equipment's are inexpensive and widely
available. ELISA can be used to detect variety of
infections.
Reagents are relatively cheap and have a long shelf life.
No radiation hazards occur during labelling or disposal of
waste.
ELISA is highly specific and
sensitive.
Easy to perform and quick procedures.

14. Disadvantages of ELISA
Measurement of enzyme can be more complex.
Kits are commercially available, but not cheap.
Very specific to a particular antigen. Won’t recognize any
other antigen.
False positives/negatives possible, especially with
mutated/ altered antigen.
Enzyme activity may be affected by plasma constituents.

15. Thank You