Response to Letter Regarding Article, “Platelet Expression Profiling and Clinical Validation of Myeloid-Related Protein-14 as a Novel Determinant of Cardiovascular Events”
We would like to thank Dr Krishnan and colleagues for their interest in our work. They have raised additional limitations of our work and question whether platelets express myeloid-related protein-14 (MRP-14). Their caution is reasonable. However, we have provided additional evidence that MRP-14 is expressed in bone marrow–derived human megakaryocytes and megakaryocytes differentiated in vitro from CD34-positive peripheral blood cells (Data Supplement Figure I of our article1). We also have detected MRP-8/14 protein in human platelets by flow cytometry (data not shown). Double antibody experiments show costaining for the platelet-specific marker glycoprotein IIb/IIIa and for MRP-8/14. MRP-8/14–positive platelets were negative for the leukocyte marker CD45, ruling out leukocyte contamination as a source of the MRP-8/14 signal.
This study was funded in part by Millennium Pharmaceuticals. Drs Healy, Damokosh, and Lillie and M.D. Pickard, T.L. Dowie, and L. Poisson are employees of Millennium Pharmaceuticals and played roles in the design of the study, data collection, data analysis, data interpretation, and the writing of the report. Drs Simon and Libby report having served as consultants and advisors to Millennium Pharmaceuticals. Dr Ridker is named as a coinventor on patents filed by Brigham and Women’s Hospital that relate to the use of inflammatory biological markers in cardiovascular disease. The other authors report no conflicts of interest.
Healy A, Pickard MD, Pradhan AD, Wang Y, Chen Z, Croce K, Sakuma M, Shi C, Zago AC, Garasic J, Damokosh AI, Dowie TL, Poisson L, Lillie J, Libby P, Ridker PM, Simon DI. Platelet expression profiling and clinical validation of myeloid-related protein-14 as a novel determinant of cardiovascular events. Circulation. 2006; 113: 2278–2284.