ABSTRACT
The aim of study was to explore the frequency of ABO type IgM antibody in infants younger than six months. 309 hospitalized infants younger than six months were selected at first and their EDTA K(3) anticoagulant blood samples were taken. All the infants were divided into five groups: neonates within 1 week as group I; neonates aged 8 to 14 days as group II; neonates aged 15 days to 1 month as group III; infants aged two to 3 months as group IV and infants aged 4 to 6 months as group V. The monocolonal anti-A, anti-B serums, A cells, B cells and O cells were utilized to carried out the blood typing with tube test. The results indicated that from 309 samples tested 33 AB type sample were excluded. Out of the remains of 276 samples, 29 of 46 samples in group I were positive and with the ABO type consistent rate 63% (29/46); 41 of 64 samples in group II were positive and with the ABO type consistent rate 64% (41/64); 47 of 74 samples in group III were positive and with the ABO type consistent rate 63% (47/74); 28 of 45 samples in group IV were positive and with the ABO type consistent rate 62% (28/45); 40 of 47 samples in group V were positive and with the ABO type consistent rate 85%. It is concluded that the ABO type IgM antibody appear in most infants younger than six months and these IgM antibodies may be regarded as the important evidence for ABO typing in infants.