Lymphocyte proliferation in Down's syndrome measured by sister chromatid differential staining

Lymphocyte proliferation in PHA stimulated cultures from Down's syndrome patients and normals was measured by the BrdU/Giemsa method for demonstrating sister chromatid differential staining. Both Down's syndrome patients and normals had 1st, 2nd and 3rd divisions present. However, Down's syndrome patients had more 3rd division metaphases and fewer 2nd division metaphases than the normals. There was no difference in the mitotic index between the two groups.