Hematopoietic stem cells ( KKM ) are able to renew the transplant patient's hematopoietic system . Renewal is preceded by their implantation ( called homing ) in the hematopoietic microenvironment of the bone marrow . Mechanisms regulating cell implantation in the bone marrow are therefore one of the issues on which they focus research hematologists clinical and experimental studies. Adhesion molecules are identified , proteolytic enzymes and chemotactic factors involved in cell engraftment after transplantation. It is known for example, that cells derived from mobilized peripheral blood are implanted faster than cells isolated from bone marrow. In our research team indicate that an important role in early hematopoietic cells implantation found in mobilized peripheral blood , bone marrow may be derived from the so-called blood platelets . mikrofragmenty membrane which bind to the surface of CD34 + cells and enhance their adhesion to the capillary endothelium of bone marrow .