Assertion: k antigen | /r/HasProperty | detected in 1940
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text: The (https://www.ncbi.nlm.nih.gov/books/NBK2270/) K antigen (colloquially called Kell) was first detected in the 1940s as a result of a woman without the K antigen on her red blood cells being pregnant with a baby with the K antigen on the red blood cells.