MIF: A lymphokine in lens

Purpose. To examine the mechanisms of expression and functionality of macrophage migration inhibitory factor (MIF), a lymphokine and delayed early response gene expressed in equatorial cells of the lens. Methods. The genes for human and mouse MBF have been cloned and sequenced. Promoter deletions were assayed by reporter gene expression in cell culture. MIF induction by growth factors was analyzed by northern blot and by reporter gene assay. Recombinant mouse MIF was expressed using the pET system. MIF activity in lens extracts was assayed by standard migration inhibition assay. Mouse MIF sense and antisense expression vectors are being used to modify levels of MIF in cultured cells and transgenic mice. Results and Conclusions. MIF is a delayed early response gene induced by different families of growth factors and is therefore a candidate for involvement in the cascade of events from growth factor reception to lens cell differentiation. The promoter of the human MIF gene has been defined by functional analysis. The expression of MIF in the encapsulated lens and other immunologically privileged sites suggests that it has roles distinct from that of a lymphokine. Even so, the presence of MIF in lens raises the possibility that this lymphokine activity could play a part in lens-induced ocular inflammations.