A case report of anti-K natural antibody that shows reactivity at 37°C

Abstract

We detected an anti-K natural antibody from the plasma of an 80-year-old Japanese woman who had no history of red blood cell transfusion. We considered that it was an anti-K natural antibody, because the result of an unexpected antibody screening test performed nine months earlier was negative for the antibody. It showed dithiothreitol (DTT) treatment sensitivity; therefore, we considered that it was of the immunoglobulin IgM type. However, it showed reactivity at 37°C. In addition, it was detectable by the saline-indirect antiglobulin test (saline-IAT) for about three weeks. The characteristics of the anti-K natural antibody in several previous reports are partly different from those in our case, that is, the cause of the antibody production was considered to involve bacterial species. This suggests the possibility that the mechanism was exclusively bacterial involvement.