A Few Notes on Antibodies: Part 1

During my doctorate research, I shifted my research focus from more traditional biosensor technologies, such as immunosensors, to sensing applications of molecularly imprinted polymers.  However, I still dabble in immunosensors fairly often, and my expertise and previous experience in antibody-based sensors comes in handy, particularly for other researchers who come to me with questions and guidance in this field.  Here at LU, my research group is currently waiting to receive a fluorescent microscope that we recently ordered.  When the new scope arrives, I will be using it to conduct a study examining targeted antibody immobilization onto gold electrodes.  The plan is to block specific areas of our sensor substrate so that antibodies will only be able to bind to certain regions.  When fluorescent bacteria are introduced, they'll bind specifically to the antibodies, and this phenomenon should be clearly visible under the fluorescent microscope.  So in the spirit of beginning this work, I thought I'd discuss some of the basics of antibodies and antibody immobilization.  I'm going to be brief, so I may have to turn this into a series of posts.

First off, I need to clarify one thing:  when I say antibody, I am referring solely to immunoglobulin G (IgG) antibodies.  Next, I guess I should describe what antibodies are and what they do.  The IgG antibody is a relatively high molecular weight protein.  It's produced by our immune cells (B cells) in response to infection.  When the antibodies are produced during infection, they bind to the bacterium or virus or whatever, coating its surface and acting as a sort of signaling beacon.  Other immune cells are able to detect this beacon and attack and destroy the infection.  So in a very general sense, that's the natural function of antibodies.

This natural function of the IgG antibody is made possible by one of its most important properties; selectivity.  The IgG antibody is a large Y-shaped protein that looks something like this:

At the top ends of the two 'arms' of the antibody are binding sites that are capable of binding to one single antigen, which is the target bacteria or virus or whatever, and only that one antigen.  This is what is referred to as selectivity.

Researchers like me who are interested in using the properties of antibodies for biosensors and other applications must be able to readily produce or purchase these antibodies.  As it turns out, there is a fairly effective way of harvesting the antibodies that are selective for a particular antigen of interest.  Let's say, for instance, that you want an antibody that is selective for the flu virus.  To produce these antibodies, you would take a syringe that contained the flu virus and inject it into the lumen of the gut - or some other space where the antigen would not leak out into the bloodstream - of a mammal.  The mammal used is commonly a mouse, rabbit, or goat.  The B cells infiltrate the gut lumen of the animal and begin churning out antibodies that are selective for the flu virus.  Then you would go back and draw out the fluid from the lumen of the gut and purify the antibodies that were produced.  And there you have it - anti-influenza antibodies.

Having only touched the surface of this topic, there will definitely be more to come.