 Blood samples serum, plasma, DNA will be collected in every patient at time of inclusion pre-treatment and then sequentially at 3, 6 and 12 months after inclusion in patients treated with rituximab or during the remission phase for other treatments for immunological studies. When a marrow analysis is indicated, some marrow specimens will also be collected and studied and if a patient will have to undergo a splenectomy as a standard of care, some spleen specimens will also be collected. Fc gamma RIIIA VF158 polymorphism will be assessed by means of an allele-specific PCR. The sequential analysis of anti-platelets anti-GpIIbIIIa antibodies producing B cells will be performed by means of flow cytometry and ELISPOT analysis. T cells subsets will be harvested in presence of GpIIbIIIa immunodominant peptides and and cytokines expression will be measured on supernatants on days 2 and 11 in vitro by using Luminex technology in order to characterize and distinguish TH1, TH2, TH17, TFH and Tregs subsets. 