The document discusses enzyme-linked immunosorbent assay (ELISA), including its introduction, principle, equipment, procedure, types, advantages, and disadvantages. ELISA is a qualitative or quantitative immunological procedure that detects antigens or antibodies using enzyme-labeled antibodies and chromogenic substrates. It relies on antibody-antigen interactions and uses an enzyme-labeled antibody to generate a colored reaction, allowing detection of a particular antigen. The document outlines the basic equipment, general procedure involving coating wells with antibodies and adding samples and enzyme-labeled antibodies, and the three main types of ELISA - indirect, sandwich, and competitive.

1. BARKATULLAH
UNIVERSITY,
BHOPAL
ENZYME LINKED
IMMUNOSORBENT ESSAY (ELISA)
Presented by:
Navjot Singh
M.Sc. 3rd semester
Enrollment Number – R218145050002
Roll Number – 2181400013

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.
 The antigen-antibody interaction took place.
 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).

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

10. Types of ELISA
 Indirect ELISA

11. Types of ELISA
 Sandwich ELISA

12. Types of ELISA
 Competitive ELISA

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

14. Disadvantages of ELISA
 Measurement of enzyme can be more complex.
 Enzyme activity may be affected by plasma constituents.
 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.

15. References
 Kuby J., Osborne B.A, Goldsby R.A, “Immunology”, 5th edition. Pg. no 148-150
 Ochei, J. and Kolhatkar A., (2015), Medical Laboratory Science, Theory and
Practices, Tata McGraw-Hill.

16. Thank You