Identification of New Immune Factors Specific of Relapse in Childhood B Lineage Acute Lymphoblastic Leukemia

B-acute lymphoblastic leukaemia (ALL) is the most common childhood malignancy. Despite enhancement of childhood B-ALL outcome, relapses remain difficult to treat. Several studies in adult acute myeloid leukaemia have shown that proliferation of immunosuppressive cells -particularly T regulatory (Treg) cells and deficient natural killer (NK) cells- was associated with poor response to chemotherapy. However, few studies have been done on childhood ALL and none on relapse of B-ALL. Moreover, a newly described immunosuppressive B cells subset (Breg cells) seems to have a role in oncogenesis in mice model, but its significance has never been evaluated in human cancers. The purpose of this study is to prospectively evaluate the immune status of children newly diagnosed with first relapse of B-cell ALL, and to compare results with those of children treated for B-ALL in complete remission. Classic lymphocytic phenotype, proportions of immunosuppressive cells (Treg cells, deficient NK cells, Cytotoxic T-lymphocyte-associated protein 4 and/or Programmed T cell death 1) and thymopoiesis will be evaluated. The investigators assume that increase of immunosuppressive cells proportions could be associated with B-ALL relapse.