Chemotherapy alters the increased numbers of myeloid-derived suppressor and regulatory T cells in children with acute lymphoblastic leukemia.

INTRODUCTION: Acute lymphoblastic leukemia (ALL) is the most common cancer diagnosed in children. The precise mechanism behind the relapse in this disease is not clearly known. One possible mechanism could be the accumulation of immunosuppressive cells, including myeloid-derived suppressor cells (MDSCs) and T regulatory cells (Tregs) which we and others have reported to mediate suppression of anti-tumor immune responses. AIM: In this study, we aimed to analyze the numbers of these cells in a population of B-ALL pediatric patients. METHODS: Peripheral blood samples withdrawn from B-ALL pediatric patients (n = 45 before, during and after the induction phase of chemotherapy. Using multi parametric flow cytometric analysis. MDSCs were identified as Lin-HLA-DR-CD33+CD11b+; and Treg cells were defined as CD4+CD25+CD127-/low. RESULTS: Early diagnosed B-ALL patients showed significant increases in the numbers of MDSCs and Tregs as compared to healthy volunteers. During induction of chemotherapy, however, the patients showed higher and lower numbers of MDSCs and Treg cells, respectively as compared to early diagnosed patients (i.e., before chemotherapy). After induction of chemotherapy, the numbers of MDSCs and Treg cells showed higher increases and decreases, respectively as compared to the numbers in patients during chemotherapy. CONCLUSION: Our results indicate that B-ALL patients harbor high numbers of both MDSCs and Tregs cells. This pilot study opens a new avenue to investigate the mechanism mediating the emergence of these cells on larger number of B-ALL patients at different treatment stages.

Transplantation of insulin-producing cells derived from human mesenchymal stromal/stem cells into diabetic humanized mice.

BACKGROUND: The purpose of this study was to investigate allogenic immune responses following the transplantation of insulin-producing cells (IPCs) differentiated from human adipose tissue-derived stem cells (hAT-MSCs) into humanized mice. METHODS: hAT-MSCs were isolated from liposuction aspirates obtained from HLA-A2-negative healthy donors. These cells were expanded and differentiated into IPCs. HLA-A2-positive humanized mice (NOG-EXL) were divided into 4 groups: diabetic mice transplanted with IPCs, diabetic but nontransplanted mice, nondiabetic mice transplanted with IPCs and normal untreated mice. Three million differentiated cells were transplanted under the renal capsule. Animals were followed-up to determine their weight, glucose levels (2-h postprandial), and human and mouse insulin levels. The mice were euthanized 6-8 weeks posttransplant. The kidneys were explanted for immunohistochemical studies. Blood, spleen and bone marrow samples were obtained to determine the proportion of immune cell subsets (CD4+, CD8+, CD16+, CD19+ and CD69+), and the expression levels of HLA-ABC and HLA-DR. RESULTS: Following STZ induction, blood glucose levels increased sharply and were then normalized within 2 weeks after cell transplantation. In these animals, human insulin levels were measurable while mouse insulin levels were negligible throughout the observation period. Immunostaining of cell-bearing kidneys revealed sparse CD45+ cells. Immunolabeling and flow cytometry of blood, bone marrow and splenic samples obtained from the 3 groups of animals did not reveal a significant difference in the proportions of immune cell subsets or in the expression levels of HLA-ABC and HLA-DR. CONCLUSION: Transplantation of IPCs derived from allogenic hAT-MSCs into humanized mice was followed by a muted allogenic immune response that did not interfere with the functionality of the engrafted cells. Our findings suggest that such allogenic cells could offer an opportunity for cell therapy for insulin-dependent diabetes without immunosuppression, encapsulation or gene manipulations.