Mutant NMMHC-IIA polypeptide is present in leukocytes but decreased in platelets. Immunoblot analysis of isolated neutrophils, platelets, monocytes, and lymphocytes from patients 1 and 2. Whole cell proteins were separated by SDS-PAGE and resolved proteins were electroblotted onto polyvinylidine difluoride membranes. Blots were cut horizontally in half at approximate position of 75-kDa molecular marker. The top half of each blot was probed with PRB440P or NT629; bottom portions were reacted with antiactin antibody. A horizontal line has been inserted to indicate where the gel was cut. Top panels show blots probed with PRB440P and antiactin antibody. Bottom panel shows blots probed with NT629. Analysis with NT629, which recognizes only mutant NMMHC-IIA polypeptide, revealed mutant NMMHC-IIA expression in neutrophils, lymphocytes, and monocytes but obviously decreased expression in platelets. Signal ratio of NT629 to PRB440P is also obviously decreased in platelets compared with leukocytes.