[Biology and differentiation of lymphocytes in the classification of lymphomas]

The classifications of non-Hodgkin's lymphomas are briefly discussed and the processes of proliferation and differentiation of B and T lymphocytes are analyzed. The B and T lymphocytes engaged in the immune response arise from precursor cells through a two-cycle process of proliferation and differentiation: the first cycle produces cells with antigen receptors of varying specificity (resting circulating B and T lymphocytes); the second cycle produces B and T type effector cells and "memory" cells. Each phase of B and T differentiation can give rise to a type of lymphoma; in fact, malignant lymphomas can be divided into categories of precursor B and T cell lymphomas, resting B and T cell lymphomas and activated B and T cell lymphomas. Hodgkin's lymphoma could be considered a lymphoma arising from activated cells with atypical phenotype, i.e. Hodgkin and Reed-Sternberg cells. These cells secrete cytokines which recruit lymphocytes, histiocytes, eosinophils and plasma cells which form the cellular background typical of this tumor.