What indicates completely incorporated engraftment in STR PCR?

The correct answer is that full chimerism, where only donor cells are present, indicates completely incorporated engraftment in short tandem repeat (STR) PCR analyses.

When evaluating engraftment after a stem cell or organ transplant using STR PCR, the presence of only donor cells signifies that the transplant has successfully taken over the hematopoietic landscape of the recipient. Full chimerism ensures that the genetic material from the donor is exclusively present, pointing to successful integration and function of the transplanted cells without any residual recipient cells. This is crucial for determining the success of the transplant, as residual recipient cells can indicate the potential for graft rejection or failure.

Partial chimerism indicates that there is a mixture of donor and recipient cells, suggesting that engraftment is not complete, and recipient cells are still present, which could lead to complications. The presence of both donor and recipient cells suggests ongoing competition or lack of full integration. Failure of engraftment means that the donor cells are not able to establish themselves in the recipient's bone marrow or blood, which does not correspond to an indication of full engraftment. Thus, full chimerism, where only donor cells are observed, clearly indicates completely incorporated engraftment.