Clonal rearrangement of TCR-Vβ4 shown by the PCR in Patient 5's blood cells after cyclosporine therapy (B). Shown as negative controls are Patient 5's blood cells studied with Vβ1 primers (A) and blood cells from a normal donor studied with Vβ4 primers (C). The image in (A) is magnified 60-fold in relation to the images in (B) and (C). (A) and (C) show multiple small peaks produced by polyclonal rearrangements, whereas (B) shows a discrete tall peak produced by a clonal rearrangement and superimposed on a polyclonal background.