Osteoclastogenesis and lymph node organogenesis in different species of Egyptian rats

ABSTRACT

The development of lymphoid organs depends on the correct expression of several molecules within a defined timeframe during ontogeny. Although this is an extremely complex process, with each secondary lymphoid tissue requiring subtly different signals, a common framework for lymphoid development is beginning to emerge. Bone remodeling is tightly regulated by a molecular trial composed of OPG/RANK/RANKL. The receptor activator of RANKL [localized on osteoblasts] enhances osteoclastogenesis via interaction with its receptor RANK [localized on osteoclasts], whereas osteoprotegerin [OPG] [produced by osteoblasts] inhibits this osteoclastogenesis by binding to RANKL. The RANK provides critical signals necessary for lymph node organogenesis and osteoclast differentiation. The TNF family molecule OPGL has been identified as a potential osteoclast differentiation factor and regulator of interactions between T cells and dendritic cells in vitro. Thus OPGL is a new regulator of lymph node organogenesis and lymphocyte development and is an essential osteoclast differentiation factor in vivo So, the result of this study showed that lymph node organogenesis appears to require adequate quantity of RANKL, and this significant level can apparently persist despite marked overexpression of the soluble RANKL inhibitor OPG