Abstract
By analysing leucocyte subpopulations with monoclonal antisera, we have shown that the diagnosis of severe combined immunodeficiency can be made soon after birth. The technique of staining has been adapted for small blood samples, and normal ranges of leucocyte subpopulations have been established for fetal blood taken from mid-trimester pregnancies. Using this information, we gave prenatal advice to an at risk family and predicted that the pregnancy would be normal; this was confirmed after birth. This technique should allow prenatal diagnosis for severe combined immunodeficiency, especially if the phenotype of a previously affected child is known.