4 Types of ELISA (Direct, Indirect, Sandwich, Competitive)

Immunoassays all utilize the bond between an antibody and its specific antigen for them to work.

The two main categories of immunoassays are unlabeled and labeled. Labeled immunoassays consist of radio immunoassays and the much more frequently used Enzyme-linked immunosorbent assay or ELISA which we will look at today.

There are four different types of ELISA, direct, indirect, sandwich and competitive ELISA. In direct ELISA the target antigen has been bound to the floor of the micro well plate. Then primary monoclonal antibodies specific to the target antigens bind to them. Moreover, these antibodies have been labeled with an enzyme which can interact with a substrate to produce a measurable signal.

Indirect ELISA works in the exact same manner but here an additional secondary antibody binds to the primary antibody. This secondary antibody that has been outfitted with a label which produces a signal in the same manner as in the previous case.

In a sandwich ELISA, a so-called capture-antibody has been bound to the floor of the well. Then when the sample is added, the target analyte binds to the capture antibody. Then another antibody, also specific to the target analyte binds to it, forming a sort of sandwich structure. This second antibody has been labeled and can thus produce a signal.

Finally competitive ELISA works slightly different. Here, the antigen is first mixed with an excess of antibodies specific to it. These then react and form an antigen-antibody complex. Then the mixture is added to a micro-well plate containing antigens specific to the antibodies in the mixture. The result is that only unbound antibodies can bind to these antigens. Labeled secondary antibodies then bind to these primary antibodies and produce an inverse signal, meaning that the more signal we get the less antigens were present in out initial mixture of antigens and antibodies.

[LucasLearnz]

Please let me know if you found the video helpful!! Helps me stay motivated!😄

[snjtsrc]

simple, clear explanations!

One thing I would add to the indirect ELISA is that the split of one antibody into:
1 antibody only detecting the substrat and
1 antibody only binds to the first antibody and puts out signal

makes the production of substrat specific antibodies easier:
the second antibody which only binds to the first antibody and puts out signal is adaptable for any substract, and
the first antibody only detecting the substrat is easier to manufacture. :P

[Lokikashyap-gx]

Thank you....i saved a lot of time in reading for my test

[melihozdemir]

This was very short and clear. Thank you

[meryemlahbara]

Thank you very much .. a whole chapter in couple of minutes

[danilogarganese]

Sorry for my english, it is bad i know. But the enzime should not be bound to the FC part of the antibody? And the antigen should not be bound by the Fab part? In the video you show the opposite 😅

[nashmink]

please can you make a video about assay buffer or dilution t (what is thirer function in test)

[nitikadiwakar]

What are we detecting an antigen or antibody in competitive Elisa

[Manar_moh]

beautiful video ❤️‍🔥❤️‍🔥 thanks from iraq 🌸🌸

[thomaswilson]

Can this be done in reverse order?
With the wells lined with antibodies to quantify the presense of a specific antigen? Or is that when the sandwich method is employed? In the context of looking for the presence of a toxin within a water sample.

[Ravifddccvf]

Difference between cmia and immunochromatography

[bogdanator]

Your illustrations are wrong. The antigen is not bound at the Fc part but instead at the Fab. Your antibodies are inverted

[erfanjam]

This didn’t explain a thing! Talk to me like I’m three and break every little thing down please for next time!