While I'm not an expert, I know that IL-33 is an abbreviation for interleukin-33. Interleukins are a subclass of cytokines that are naturally produced within the human body. Cytokines are protiens that are produced by all cells and they act as intercellular communicators. Interleukins are cytokines that generally regulate the immune system and immune response, but they do other things too. I know mostly about interferons, another kind of cytokines involved in immune system activity. You have to realize that these cytokines are manufactured using recombinant DNA technology. That means that the gene that produces the specific protien is taken from human DNA and fired into bacteria with a gene gun. The bacteria then produces the protien as a waste product. That protien is then injected back into people at high doses as a treatment. The thing with most cytokines is that although all cells are capable of creating then at various times, the y are highly unstable proteins and can't travel long distances in the body. They usually can only travel to adjacent cells and break down quickly in the intercellular fluid. So basically what they're doing is giving your intire body a massive dose of something it already makes. While that protien is rapidly breaking down in your body, for a brief time it's communicating to a large percentage of your cells to illicit a specif response, in this case which ever response the article indicated- I didn't read it. So you shouldn't worry about taking drugs like these too much. I took very high doses of intereferon a-2a for many years in a row back in the early 1990s for hepatitis c before I was finally cured of it. There are no known long term side affects for long term interferon use, and I suspect it's a similar situation with most therapeutic cytokines.