Novel Example of a Direct-Agglutinating Anti-Ku.

Background: Several Kell-system antibodies are known to cause direct agglutination. Also, some specificities, such as anti-Ku, have been reported to react only via the indirect antiglobulin test (IAT).
Methods: Herein, we describe the case of a 61-year-old alloimmunized white woman who presented to an outside hospital with a gastrointestinal (GI) bleed and a "possible anti-Ku" was reported with 3+ reactivity at PEG-IAT and at Ficin-IAT; in addition to an unidentified cold antibody. Subsequently, when the patient presented to a second outside hospital, an anti-Ku that caused 3+ to 4+ reactions at saline-immediate spin (IS) was identified. The reactivity was evaluated with 0.01-M dithiothreitol (DTT) treatment of the plasma.
Results: It was determined that the strong agglutination with saline-IS was caused by immunoglobulin (Ig)M anti-Ku.
Conclusion: To our knowledge, this is the first reported case of an IgM anti-Ku.
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