ANTI-Sc2 IN A JAPANESE PREGNANT WOMAN WITHOUT APPARENT SENTITIZATION

We report a case of naturally occurring anti-Sc2 found in a Japanese pregnant woman with Rh (D) negative phenotype. She has no history of blood transfusion, and experienced two normal deliveries. Anti-Sc2 was found in the serum at the 13th week of gestation in her third pregnancy. Antibody titer by indirect antiglobulin test was 1: 2. The antibody was also detected by low isonic strength polybrene (LISP) method in the AutoAnalyzer (Technicon-AAII). In addition to anti-Sc2, anti-D appeared at the 17th week (1: 8 by indirect antiglobulin test) and reached the maximum (1: 32) at the 36th week. In contrast, anti-Sc2 decreased to the level at which only LISP method can detect it after the 20th week. A boy was born at the 38th week and received phototherapy for neonatal jaundice. Cord blood was positive for direct antiglobulin test. Only anti-D was detected on the red cell surface. Red cells from this woman, her husband and their children including a new born were all negative tested for Sc2 antigen. It is suggested that this woman has developed anti-Sc2 in the course of pregnancy without exposure to Sc2 antigen. The mechanism of this antibody production remains to be investigated.