Positive minor cross-reaction due to red blood cell T-activation in a neonate with perforated colon.

We report the case of a prematurely born, 39-day-old male infant with a history of mechanical ileus and perforated colon in which blood grouping showed group 0 Rh (D)-positive without particularities. Minor tests, however, were distinctly positive in 4 units of blood, whereas all major tests were negative. There is strong evidence that the positive minor cross-reaction was caused by in vivo RBC T-activation with subsequent donor serum anti-T agglutination.