Indirect ELISA

Indirect ELISA is used for detection of a particular antibody in a given sample. Most of the HIV diagnosis kits use indirect ELISA principle.

Indirect ELISA
In this type of ELISA, the antigen (viral coat in case of HIV) are adsorbed to the walls of well.

Antibodies from patient are then added to the well.

If the patient is HIV positive he will produce antibodies against the HIV antigen and if he is HIV negative, there won’t be any antibodies against the antigen.

After that, detection antibodies which will recognize human antibodies are added.

The unbound detection antibodies are washed off followed by substrate addition.

If the sample contains antibodies against HIV, it will show a colour change due to the detection antibody bound to it.

If the sample is HIV negative, it won’t show ant colour change as it does not have any bound detection antibody.

Written by Komal Kadam
Illustration by Immense Immunology Insight

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