Characterization of signals leading to clonal expansion or to cell death during lymphocyte B cell activation.

The immune system is endowed with a multitude of different mechanisms to eliminate, paralyze or neutralize T and B lymphocytes expressing self-reactive antigen receptors that might endanger the individual’s life. The ability of both types of lymphocytes to recognize and react to different stimuli is a learning process that occurs during lymphocyte differentiation, and the mechanisms implicated in self-tolerance intervene at determined control points following developmental criteria. B and T lymphocyte differentiation from committed precursor cells into antibody-secreting plasma cells or effector T cells proceeds through multiple steps that are defined by changes in the expression pattern of lineage-specific genes (Moller 1994).