Abnormal fetal immunological development in Down's syndrome.

OBJECTIVE

To investigate the intrauterine development of the immune system in Down's syndrome.

DESIGN

Cross sectional study.

SETTING

Harris Birthright Research Centre for Fetal Medicine, London, UK.

SUBJECTS: 16 fetuses with Down's syndrome and 104 fetuses with a normal karyotype at 17-24 weeks gestation.

MAIN OUTCOME MEASURE: Flow cytometry was used to enumerate T (CD3+), B (CD19+) and NK (CD3- & CD16+/CD56+) lymphocyte subpopulations in fetal blood obtained by cordocentesis.

RESULTS

The median numbers of T, B and NK lymphocytes in fetuses with Down's syndrome (1.52 x 10(9)/l, 0.08 x 10(9)/l, and 0.10 x 10(9)/l, respectively) were significantly lower than in the chromosomally normal fetuses (T lymphocytes: 1.98 x 10(9)/l, z = 3.04, P < 0.01; B lymphocytes: 0.50 x 10(9)/l, z = 5.84, P < 0.0001; and NK lymphocytes: 0.19 x 10(9)/l, z = 3.14, P < 0.01).

CONCLUSION

These data demonstrate that in Down's syndrome, there is abnormal intra-uterine development of the immune system.