Investigators could not identify subjects who met all inclusion criteria.

Individuals who experience traumatic injury often require blood transfusion. In some individuals who receive blood after an injury, white blood cells from a person who donated blood may remain in the body for years, a condition known as microchimerism. This study is designed to examine a group of people who are known to have long-term microchimerism and, through analysis of their blood, determine whether there is evidence that the microchimerism involves blood stem cells that can become any type of blood cell (red blood cells, white blood cells, or platelets) and that might be a permanent part of the body.

Transfusion-associated microchimerism, the persistence of donor white blood cells months or years after transfusion in the recipient, has been observed in approximately 10-15% of transfused trauma patients. Previous studies suggest that the microchimeric cells include multiple immunophenotypes of leukocytes (CD4+, CD8+, CD15+, and CD19+) and that they can persist for decades, features suggestive of hematopoietic engraftment.

In this study, ten subjects known to have long-term microchimerism will undergo either leukapheresis (a blood filtering procedure) or collection of a 500 mL whole blood sample (the amount of a standard blood donation). These samples will then be analyzed to determine whether the microchimeric (donor) cells include hematopoietic stem cells (CD34+) and precursor cells in the red blood cell, white blood cell, and platelet lineages.

Inclusion Criteria:

• Demonstrated long-term microchimerism following transfusion for traumatic injury

Exclusion Criteria:

• Prior bone marrow or solid organ transplantation
• Pregnancy
• Blood transfusion within the past 12 months

Previous study participants