Abstract: The invention relates to antibodies directed against APRIL (A Proliferation Inducing TNF Ligand, also known as TALL-2), in particular the monoclonal antibody Aprily-2, hybridoma cells producing monoclonal antibody Aprily-2, and the use of a combination of an antibody against membrane-anchored APRIL and Aprily-2 in the diagnosis of B cell lymphoma resistance to treatment and the prognosis of clinical development of Diffuse Large B-Cell (DLBCL) lymphoma from high risk patients (>60 years and International Prognostic Index >2). An amino acid sequence GTGGPSQNGEGYP called Stalk, useful in the preparation of antibodies, is described.