Remarkable Positive Correlation of Blood Monocyte Counts with Blood Plasmacytoid Dendritic Cells and Blood Regulatory T Cells.

In order to clarify the pathophysiology of immune state after stem cell transplantation and investigate the interaction of immune competent cells each other, quantitative analysis of blood plasmacytoid dendritic cell (pDC), myeloid dendritic cell (mDC) 1, mDC2 and regulatory T cells (Treg) was performed in normal persons and the patients who received allogeneic stem cell transplantation. pDC was identified as CD1c (BDCA-1)⁻ and CD303 ((BDCA-2)⁺ cells by flow cytometry analysis. The identified pDC was confirmed by the additional characters of CD11c⁻, CD4⁺, CD304 (BDCA-4)⁺ and CD123^high. mDC1 was identified as lineage (CD3, CD14 and CD19)⁻ and CD1c (BDCA-1)⁺ cells. The identified mDC1 was confirmed by the additional characters of CD11c⁺⁺⁺ and CD14⁻. mDC2 was identified as CD303 (BDCA-2)⁻ and CD141 (BDCA-3)⁺ cells. The identified mDC2 was confirmed by the additional characters of FcR (CD32 and CD64)⁻. Treg was identified as surface CD4⁺ and cytoplasmic Foxp3⁺ cells. The identified Treg was confirmed by the additional characters of CD25^high, CD64L⁺ and CTLA-4⁺. Sixty seven blood samples from normal persons and the patients who received stem cell transplantation were analyzed. Normal values were demonstrated as follows; pDC is 0.30 + 0.15% of blood mononuclear cells (MNC), mDC1 is 0.60 + 0.21% of blood MNC, mDC2 is 0.06 + 0.06% of blood MNC, and Treg is 1.52 + 1.27% of blood lymphocytes. Cell counts per ml of each cells were calculated from percentages of each cell fraction and the number of mononuclear cells, and the volume of the blood sample. As to the patients with stem cell transplantation, the percentages of pDC, mDC1, mDC2 and Treg were distributed in a wider range than normal values, covering normal limits. Although the values of pDC, mDC1 and mDC2 were not correlated with the durations after stem cell transplantation or the presence of GVHD, Treg cell counts were significantly correlated with the durations post transplantation. The longer duration from the day of stem cell transplantation to blood sampling, the more Treg cells were present in the blood of the transplanted patients. The percentages of pDC, mDC1, mDC2 and Treg were investigated as to their correlationship with values of blood monocyte, which percentage was evaluated as cells in monocyte area of FSC/SSC dot plot figures of flow cytometry. Although the correlation between mDC1 or mDC2 and blood monocyte counts was not identified, the percentages and cell counts of blood pDC were demonstrated to have a significant correlation with blood monocyte counts (p<0.0001) in normal persons and the transplanted patients. In addition, it was identified that percentages of blood Treg cells in lymphocyte fraction or blood Treg cell counts were significantly correlated with blood monocyte counts (p<0.0001) in normal persons and the patients. The present findings that blood monocyte counts are associated with the frequency of blood pDC and Treg cells suggested that monocytes or monocyte-related cytokines may have some roles in generation and regulation of blood pDC or Treg cells.