ABSTRACT
The major sites for the production of T and B cells are the thymus and the bone marrow respectively. In the thymus, T cells develop from progenitors initially generated in the bone marrow which then migrate to and therein differentiate to mature T cell progeny. In the bone marrow, B cells are generated from B-lymphoid committed cells derived from hemopoietic stem cells resident in that organ. In vitro studies have established that numerous cytokines may play a role in B and T-cell development. However, most single cytokine knockout mice show apparently normal B-and T-cell development. In contrast, interleukin-7 (IL-7)-deficient mice present dramatic alterations in both the thymus and bone marrow. Indeed, in these organs, lymphocyte cellularity is abnormal demonstrating the importance of IL-7 in B and T-cell development and the absence of cytokine
redundancy for its activity. In this review, we will outline some of the characteristics and the function of both IL-7 and its receptor in the context of an IL-7-overexpressing transgenic mouse line that we have generated and also provide evidence that IL-7 may be involved in the development of lymphoid tumours.
