Enumeration of functionally active anti-Aspergillus T-cells in human peripheral blood.

Invasive aspergillosis remains a life-threatening complication in patients undergoing allogeneic stem cell transplantation (SCT). Since CD4(+) T-cells provide a critical secondary defense against Aspergillus spp., the quantification of "functional" anti-Aspergillus T-cells might be important in the clinical care of allogeneic transplant patients. We present a rapid, simple and reproducible method to enumerate functionally active, cytokine-producing anti-Aspergillus T-cells in peripheral blood by means of flow cytometry, by which these cells were also phenotypically characterized as memory CD4(+) T-cells. When using 100,000 PBMCs and requiring a minimum of 50 events, at least one anti-Aspergillus T-cell among 1000 CD4(+) T-cells can be detected. Compared to healthy individuals, the number of anti-Aspergillus T-cells in patients up to one year after SCT was significantly lower. The presented method might help to define hematopoietic transplant recipients who will benefit from adoptive transfer of anti-Aspergillus T cells.