Différenciation lymphoïde B: Physiologie, méthodes d'exploration et application à l'étude des proliférations B

B-cells are produced in the bone marrow, where they rearrange their Immunoglobulin (Ig) chain genes. They leave the marrow as naïve B-cells. Some of them begin recirculating through blood and secondary lymphoid organs (lymph nodes, spleen, and mucosae-associated lymphoid tissue) until encounter with the antigen. At that point, they start proliferating et transforming in antibody-producing cells, or they undergo affinity maturation through somatic hypermutation with class switch recombination in a germinal center. Subsequently, they become either memory B-cells or plasma cells. Other naive B-cells traffic to marginal zones of secondary lymphoid organs and will give rise to a quick production of antibodies when stimulated by encapsulated bacteria. Lymphomagenesis involves acquired modifications of the genome facilitated by physiological Ig chain gene rearrangements, somatic hypermutations and class switch recombination. Accordingly, frequent translocations occur in Ig chain genes. Repeated stimulations through the B-cell antigen receptor (BCR), increasing frequency of genomic alterations, are also involved in lymphomagenesis, as well as microenvironmental factors. The current classification of lymphoproliferative disorders of B-cell origin is the one issued by the WHO, based on morphology and immunophenotyping, and completed with detection of genetic alterations using cytogenetics, classical or FISH, or molecular biology. DNA microarray is a recent, complex and promising technique activally used currently to define new classes of lymphoma, which should generate significant improvements in this field.