When researchers studied cetuximab in clinical trials, they reported serious allergic reactions in 3 percent of patients taking the medicine. But when the drug became widely available, a significantly higher number of patients in Tennessee and North Carolina -- more than 20 percent -- had severe allergic reactions when they began using the same drug.
Researchers studying the geographical differences eventually discovered that most of the people who had an allergic reaction to cetuximab also had a previously existing antibody in their blood that targeted a specific sugar on the cetuximab molecule, causing the immune response.
"The antibodies were there before they were treated, and they predicted what happened to them," said Platts-Mills, who co-authored the research paper.
So where did the antibody come from, and why do more people in Tennessee and North Carolina have it?
Platts-Mills theorizes that patients developed the antibody before they took the drug when their bodies staged "a very aggressive immune response" to a seed tick bite, but he has yet to determine exactly why the person makes this particular antibody after the bite.
"In the area where this thing is going on, tick bites are much more common than people realize," said Platts-Mills.
The ongoing research is being closely followed by other allergists intrigued by the findings.