Feature of immunoglobulin heavy chain complementarity determining region 3 gene in neonates with different gestational age / 中华微生物学和免疫学杂志

ABSTRACT

Objective　To study the feature of immunoglobulin complementarity determining region 3 (CDR3) gene in neonates of different gestational age (GA), and the effect of neonatal maturity on the diversity of CDR3 nucleotide sequence. Methods　DNA were extracted from cord blood of 10 neonates of very immature (25-30 weeks), 12 immature (31-36 weeks), and 11 mature (37-41 weeks). CDR3 sequence was amplified suing nested PCR technique then cloned and sequenced. Results　1. There was a CDR3 length of 29.4±7.8, 32.4±9.2 and 40.8±10.7bp, including NDN length of 13.5±5.6, 16.1±7.8 and 22.0±8.5bp respectively in very immature, immature and mature neonates. 2. DP73 and DP75 were preferentially used in very immature and immature neonates, VH5, DP73 and DP75 were used in mature neonates. The usage rate of DP73 and DP75 reduced, whereas VH5 was raised with GA increasing. 3. For D gene segment, there was a frequent use of DN, DQ52 and DXP in very immature neonates, whereas DXP, DLR and DN in immature and mature neonates. 4. JH4 usage was preferential, followed by JH6 in all neonates, and their usage rate was decreased with GA increasing. 5. 63.3%, 68.8% and 92.0% of CDR3 sequence respectively in very immature, immature and mature neonates have an open reading frame with 303bp long encoding 101 residues. Conclusion　During the early life of neonates, VH-D-JH rearrangement of IgH gene is in an active condition, but the diversity is limited. Humoral immunity is a gradual development with increasing GA. Both heterogeneity and similarity of CDR3 sequence exists in neonates with different GA.