| The innate immune response of the postulated membrane-bound fgl2 as a prothrombinase has been implicated in the pathogenesis of viral-induced hepatitis, fetal loss syndrome, and xenograft rejection. However, soluble (secretory) fgl2 protein is also expressed by T cells. Since fgl2 has a conserved fibrinogen-related domain (FRED) at the C-terminal, it is postulated soluble fgl2 plays a role in the adaptive immune response like other members of the fibrinogen-related protein family. We, therefore, speculate soluble fgl2 has T cell immunoregulatory activities that are functionally distinct from the membrane-bound fgl2 in macrophages and endothelial cells. In this study, we generated functional soluble fgl2 protein using the baculovirus expression system. Furthermore, soluble fgl2 protein inhibited T cell proliferation in a one-way xenogeneic mixed lymphocyte reaction. Molecular studies showed multiple fgl2 mRNA species existed in Con-A activated T cells, indicating that these mRNA species could express soluble fgl2 protein secreted by T cells. |
