In order to explain how monoclonal antibodies work, Meghan May, a professor of microbiology and infectious disease at the University of New England, first wanted to talk about how all antibodies work. And to do that, she wanted me to do the YMCA. I raised my arms obediently, feeling a little silly as we spoke over the phone.

An antibody molecule is kind of shaped like a Y, she said. The stalk partthats your legs, touching the flooris called the constant region. And the hands-in-the-air part is called the antigen-binding region.

Humans have five different types of antibodies: IgM, IgG, IgE, IgD, and IgA. The first two are most relevant to the SARS-CoV-2 conversation. When you have a recent infection, you have a lot of IgM antibodies, but as the infection fades, theyre replaced with the longer-lasting IgG. The constant region of these antibodies, as you might expect from the name, doesnt change much from person to person.

But the antigen-binding regionsthe armscan differ dramatically from person to person. Those are the parts that are really fine-tuned and specific for different viruses, different bacteria, different pollen grains, May said. When our antibodies first encounter a new virus, they immediately start trying different things, bringing out the whole arsenal of antigens that might work on the new intruder. What seems to work well against SARS-CoV-2 is antigens that bind very tightly to the coronaviruss spike protein, basically grabbing it in a chokehold to prevent it from attaching to our cells and keep the disease from progressing. In other words, May said, good SARS-CoV-2 antibodies are sticky. Some, she said, are more like a preschoolers glue stickwhich is to say, sticky in name only. Others are more like superglue. Its the superglue level of antigens that work well in lab tests, latching on to the virus and neutralizing it.

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