Monitoring of Measles-specific Immune Status in Adult Allogeneic Hematopoietic Stem Cell Transplant Recipients

Inclusion Criteria: Study population: * Aged ≥ 18 years and ≤ 75 years, * Have received an allo-HSCT ≥ 24 months ago, * In complete remission of initial hematologic disease and with successful engraftment (recipient chimerism \<0.3% on whole blood), * Without extensive chronic GVHD, * Having given their written consent, * Affiliated to a social security plan, * Able to attend all scheduled visits and to comply with all study procedures. Healthy volunteers: * Aged ≥ 18 years and ≤ 75 years, * Having a history of measles (=convalescent) or have been vaccinated in the past with two doses of MMR (=vaccinated), * Having given their written consent, * Affiliated to a social security plan. Exclusion Criteria: Study population: * History of autoimmune disease or acquired immunodeficiency (other than the hematological disease), * Patients undergoing pharmacological immunosuppression or biotherapy or extracorporeal photopheresis at the time of inclusion, or whose immunosuppressive treatment (corticosteroids and anti-rejection agents) has been stopped less than 3 months ago, or whose biotherapy (anti-cytokines, anti-JAK, anti-CD20 etc.) has been stopped less than 3 months ago (12 months for anti-CD20 including rituximab), or whose extracorporeal photopheresis has been stopped less than 3 months ago, * Patients having received ≥ 1 infusion of IVIG in the 8 months prior to inclusion, * Patients whose last HSCT was an autograft, * Patients with known chronic active infection with human immunodeficiency virus (HIV) and/or hepatitis B or C virus(es), * Patients deprived of liberty by judicial or administrative decision, * Patients under legal protection or unable to consent to the study, * Patients participating in another interventional research study with an exclusion period still in progress at pre-inclusion, * Pregnant, parturient or breast-feeding women. Healthy volunteers: * History of autoimmune disease or acquired immunodeficiency, * History of pharmacological immunosuppression or biotherapy discontinued less than 3 months ago (12 months for anti-CD20 including rituximab), * History of IVIG infusion in the 8 months prior to inclusion, * Persons deprived of liberty by judicial or administrative decision.