The Smithsonian’s first collection of serum therapy, donated by the drugmaker Parke, Davis in 1898. (Smithsonian Institution)

Antibodies — the proteins your immune system uses to fight disease — were once a scientific mystery. Today, technology based on antibodies harnesses the body’s immune system to diagnose disease, halt epidemics and increase immunity.

Now, an online exhibition at the Smithsonian National Museum of American History celebrates the history of that technology. It’s more fascinating than you might think. “The Antibody Initiative” is a website that tells the story of antibodies through more than 1,000 objects in the museum’s collection.

Antibody tech reaches back to the 18th century, when such scientists as Edward Jenner started tinkering with ways to provoke the body’s immune response. His smallpox vaccine, introduced in the 1790s, opened up a whole new world of scientific possibility.

In the “Eradicating Smallpox” area of the site, two very different cards help tell that story. A quaint, handwritten card celebrates the effectiveness of the vaccine in 12 Massachusetts children in 1809. In contrast, a World Health Organization poster shows a hand covered in a swollen, pustular rash. The poster is an example of how vaccination efforts spread worldwide in the 20th century. In 1980, the WHO declared the disease eradicated.

Antibody tech has another side, too: diagnosis. For example, when a woman becomes pregnant, her placenta produces human chorionic gonadotropin, or HCG. Pregnancy tests incorporate an antibody that reacts to HCG when a woman’s urine contains the hormone, and the exhibition has a large number of early examples that show the ways the tests’ design has changed over the years.

The website also includes signs once used to warn people of diseases such as whooping cough and a set of forceps used to force open the jaws of people with tetanus, or lockjaw.

Every object has its own history, but collectively they illustrate the larger sweep of antibody technology and the ways it has changed health and daily life. “The Antibody Initiative” is part trip down memory lane, part warning about how bad the diseases of the past could be.