Currently, it seems to be the only one among the freely available online dictionaries that includes the immunological sense of the word "antihuman":
I thought that this was a recent addition; but a bit of digging revealed that Merriam-Webster's Medical dictionary already included this definition in 1995:
The reason I found that definition peculiar was that, although formally M-W is correct, the phrase "antihuman antibodies", written in this shorthand way without any additional modifiers, would most likely have a very specific meaning, which is antibodies against human antibodies. There is a record of this phrase in this meaning in COCA, although, ironically, the authors of the cited passage (from a 2012 article) are French.
Here's a good example from a book where the author isn't particularly careful with his words and is using the shorthand:
