Functional activity of SD lymphocytes. Donor lymphocytes from the allograft, before and after SD, were tested for alloreactivity in the HTLp frequency assay (n=11) against (A) the HLA-identical recipient stimulator cells and (B) an HLA-mismatched pooled third-party stimulator. Results are reported as the calculated frequency of alloreactive HTLp (1/x). Mean HTLp frequency for the group is indicated by gray horizontal bars (values given in graphs), and statistical significance calculated by the paired Student t test.