[Cellular origin of human B-cell neoplasms and Hodgkin's disease based on analysis of somatic hypermutations in the immunoglobulin variable region genes].

In response to antigen stimulation, B cells undergo a germinal center(GC) reaction such as somatic hypermutations of the immunoglobulin variable region genes, which results in the production and selection of antigen-specific antibodies with increased affinity. Therefore, somatic hypermutations are considered to be a hallmark of GC B cells and their descendants. Pre-GC B cells(precursor B cells, immature B cells, naive B cells and CD5+ B cells) carry no somatic hypermutations, whereas GC B cells and post-GC B cells(memory B cells and plasma cells) express somatic hypermutations. This phenomenon is useful in identifying the cellular origin of various B-cell neoplasms. Precursor B-lymphoblastic leukemia/lymphoma, mantle cell lymphoma, and most B-CLL originate from pre-GC B cells, and follicular lymphoma, Burkitt's lymphoma, marginal zone B-cell lymphoma, diffuse large B-cell lymphoma and myeloma from GC B cells or post-GC B cells. Nodular lymphocyte-predominant Hodgkin's disease and most classical types of Hodgkin's disease are derived from GC B cells. Most human-B cell neoplasms including Hodgkin's disease are derived from GC B cells or their descendants. Molecular processes that modify the DNA of GC B cells, such as somatic hypermutation, class switching and receptor editing occur in the environment of the GCs, and increase the risk of malignant transformation.