Alveolar hydatid cyst induced amyloid enhancing factor (AEF): physicochemical properties and abolition of AEF activity by serine protease inhibitors.

Cell free supernatants prepared from amyloidotic liver, unfractionated and fractionated peritoneal and spleen cells from casein stimulated (16 h post-injection) or alveolar hydatid cyst-infected (7 or 12 weeks post-infection, p. i.) C57BL/6J mice were used to assess amyloid enhancing factor (AEF) activity and to determine its cell-source and physicochemical properties. Of the various supernatants used, the plastic adherent spleen cell lysate (95% macrophages) from 7 weeks p.i mice showed greater AEF activity, on a cell to cell basis, than the lysates prepared from whole spleen cells, peritoneal exudate cells or nonadherent (96% lymphocytes) spleen cells. Culture supernatants obtained from Con A, LPS or the parasite antigen stimulated amyloidotic spleen cells but not the normal mouse spleen cells contained AEF activity; the supernatant from unstimulated amyloidotic spleen cells was negative for AEF activity. AEF was precipitated with 25% and 50% saturation with (NH4)2SO4 and after gel-filtration the low molecular weight fraction contained the AEF activity which on SDS-PAGE resolved into three peptides ranging between mol. wts 15,000 and 31,000. Of the various specific and nonspecific protease inhibitors tested, AEF activity was completely abolished by 30 min preincubation with 10 mM phenylmethylsulphonyl fluoride. Taken together, these results indicate that AEF may be a small molecular weight lysosomal neutral protease of neutrophil/macrophage origin.