The long road to functional maturity for developing T cells

Abstract

The past two years have clarified the role of the thymus as a filter for T cells with appropriate recognition specificities. What remains a knottier problem is the role of the thymus as an inductive microenvironment for changes in the regulation of genes involved in effector function - that is, making T cells into competent elements in immune defenses. It is still uncertain to what extent the functional role of a T cell - as an nterleukin 2 (IL-2)-producing helper, an IL-4-producing helper, or a killer expressing granzymes and perforin - is irreversibly determined by intiathymic events. Another, related question is whether the stimuli required by a cell to induce expression of any of its 'response' genes may also change in development, through maturation of specialized signal transduction pathways. If so, some differentiation events that profoundly affect the immunological role of T cells might be subtle and difficult to score.

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