Single-strand conformation polymorphism (SSCP) analysis of XHIM family A with T254M mutation. PCR products (198 bp) of exon 5 of the CD40L gene were denatured and run on a 12.5% polyacrylamide gel at 150 V for 14 hours. The 2 control (C) lanes show the positions of the DNA strands of the unaffected X-chromosome. The C → T mutation leads to a shift in the position of these bands, as is shown in lane 1 (XHIM patient no. 2). Carriers (lanes 2 and 3) show both mutated and unmutated DNA strands. Noncarriers (lane 4) only show the unmutated DNA strands.