CD34+ immune suppressive cells in the peripheral blood of patients with head and neck cancer.

Patients with head and neck squamous cell carcinoma (HNSCC) have profound defects in their immune defenses. Using immunofluorescent staining and flow cytometric analysis, we found that most patients with HNSCC have increased levels of CD34+ cells within their peripheral blood. These circulating CD34+ cells contribute to the depressed functional competence of the peripheral blood T-lymphocytes. This was demonstrated by the increased level of proliferative responsiveness to interleukin-2 by the patients' peripheral blood T-cells after depletion of CD34+ cells. These results show the importance of CD34+ cells in contributing to the depression of T-lymphocyte function in patients with HNSCC and suggest that strategies designed to reduce the levels of circulating CD34+ cells may enhance the immune reactivity of the patients' circulating T-lymphocytes against the HNSCC.

Cultures derived from peripheral blood CD34+ progenitor cells of head and neck cancer patients and from cord blood are functionally different.

Patients with head and neck squamous cell carcinoma (HNSCC) have profound immune defects mediated, in part, by an increased number of immune suppressive CD34+ progenitor cells in their peripheral blood and tumor. One means of overcoming this immune suppression is to stimulate the CD34+ cells to differentiate into more mature, nonsuppressive progeny such as dendritic cells or monocytes. This study determined that CD34+ cells from the peripheral blood of HNSCC patients have the same potential to differentiate into dendritic cells as do human umbilical cord blood CD34+ cells following 12-16 days of culture with a cytokine cocktail. When compared functionally, the cultures that developed from CD34+ cells of cord blood were able to induce an allostimulatory response in naive T-cells, while the cultures that developed from patient CD34+ cells lacked allostimulatory ability. Both cultures expressed class II MHC (HLA-DR), but the proportion of cells expressing the costimulatory molecules CD80 and CD86 was significantly less in cultures that developed from HNSCC-patient CD34+ cells. Therefore, although the CD34+ cells from the peripheral blood of HNSCC patients can differentiate into dendritic cells, their allostimulatory capabilities are impaired, raising the question of their potential effectiveness in stimulating antitumor immune responses.