Complex kinetics of binding of human alpha-2 interferon to human, but not bovine cells

Complex binding of the embryonic interferon, ovine trophoblast protein-1, to endometrial receptors

Ovine embryos produce an interferon (IFN)-alpha II in significant quantities during early pregnancy. This IFN, previously termed ovine trophoblast protein-1 (oTP-1), is a 172-amino-acid polypeptide which has been suggested to be the causal agent in maternal recognition of pregnancy in the ewe. Here we report the binding of oTP-1 and a recombinant bovine IFN-alpha I1 (rBoIFN-alpha I1; 165-166 amino acids long) to membrane preparations from ovine uterine endometrium. Both oTP-1 and rBoIFN-alpha I1 competed with each other for receptor binding. Based on Scatchard analysis, [125I]oTP-1 binding was determined to be complex and resolvable into a high-affinity (Kd = 3.8 x 10(-11) M, 30 fmoles/mg protein) and a low affinity (Kd = 1.7 x 10(-10) M; 96 fmoles/mg protein) component. Conversely [125I]rBoIFN-alpha I1 bound to only a single high-affinity receptor (Kd = 6.1 x 10(-11) M; 174 fmoles/mg protein). Cross-linking experiments using disuccinimidyl suberate revealed that [125I]oTP-1 associated with membrane polypeptides of two molecular weight classes (Mr 100,000 and 70,000), and could be displaced from both with rBoIFN-alpha I1. In contrast, [125I]rBoIFN-alpha I1 cross-linked to only the 100,000 Mr membrane polypeptide. These data provide evidence that the binding parameters of oTP-1 and rBoIFN-alpha I1 to endometrial receptors are different.

Regulation of cell growth by interferon

Interferons can regulate growth and differentiation in a wide range of cell types. These mechanisms are currently being examined. Interferons inhibit the growth of tumour cells and are thus potential anti-cancer agents. They can also inhibit normal cell growth in vitro, and stimulate tumour cell growth in vitro. They may also be involved in some autoimmune diseases. This review examines the effect of interferons on cell proliferation, function, and growth, focusing primarily on in vitro cell systems.

Monoclonal antibodies, electrophoretically transferred from polyacrylamide gels, retain their ability to bind specific antigens

Antibodies subjected to SDS-polyacrylamide gel electrophoresis and transferred to nitrocellulose paper, have been found to retain the ability to bind specific antigen. This has been demonstrated for two groups of antibodies, directed to a) a large molecular weight glycoprotein of the human milk fat globule and b) human interferon alpha 2. Immunoreactive antibody fragments produced by protease digestion could also be identified in this way on Western blots, thus permitting the development of optimal conditions for digestion, without the need for extensive purification procedures.

Antiviral and antiproliferative effects of interferons in quiescent fibroblasts are dissociable

Quiescent mouse Swiss 3T3 cells or human fibroblasts treated with interferon for only 2 hr before the addition of serum are effectively protected against virus infection for up to 24 hr after the addition of serum and the removal of interferon. In sharp contrast, exposure of quiescent fibroblasts to interferon only before addition of serum or the peptides epidermal growth factor and insulin, has no inhibitory effect on cell proliferation. Further, even when interferon is added after the addition of growth factors, an exposure of several hours is required to inhibit stimulation of DNA synthesis. These findings strongly suggest that the antiviral action of interferons is dissociable from their ability to inhibit cell proliferation. The implications of these findings for elucidating the molecular events leading to the biological responses elicited by interferon are discussed.