Macrophage Procoagulants

Shands, Joseph

Abstract

In the past year, we completed studies of the metabolic requirements for the production of Factor VII-like material and tissue factor by exudate macrophages. This work was presented at the FASEB and has been published. To further substantiate our evidence that macrophages do make Factor VII, we also studied the formation of Ca?2+? dependent complexes between the soluble """"""""Factor VII"""""""" and the particulate tissue factor of mouse brain and of endotoxin-stimulated macrophages. The """"""""Factor VII"""""""" does complex in a Ca?2+?-dependent way; and the complexing to macrophages behaves in a manner similar to the complexing to mouse brain, suggesting that the complexing is to tissue factor. We found that not all macrophages meke Factor VII. Peritoneal exudate cells elicited with fetal calf serum, metaperiodate, and 50 micrograms of endotoxin do not make significant amounts of Factor VII. Therefore, Factor VII is not a constitutive product of the macrophage line. Either a stimulus or maturation of the monocyte-mecrophage is required to enable the cell to make the factor. Currently we are studying the production of Factor VII by bone marrow macrophages in an attempt to define the determinants for Factor VII production. Of interest, culture supernatants of bone marrow macrophages contain the largest amount of Factor VII on days 2.5 to 5 of culture; thereafter the amount decreases. Conversely, these cells fail to respond to endotoxin with tissue factor production at day 2.5; but the responsiveness progressively increases to day 15. We are now relating tissue factor production with the production of Factor VII and plasminogen activator. We have developed rabbit antibody to mouse tissue factor and Factor VII which neutralizes their activity at dilutions of 1:32. We are now looking at the specificity of these antibodies via Western blots of macrophage membrane antigens and macrophage supernatants. (MB)