Mr 25,000 heparin-binding protein from guinea pig brain is a high molecular weight form of basic fibroblast growth factor.

A Mr 25,000 form of basic fibroblast growth factor (bFGF) has been isolated from guinea pig brain along with the typical Mr 18,000 form. Both forms were purified to homogeneity by a combination of heparin-affinity chromatography and ion-exchange chromatography on an FPLC Mono S column. The Mr 25,000 form, like the Mr 18,000 form, was not eluted from the heparin-affinity column with 0.95 M NaCl, but was eluted with 2 M NaCl. The Mr 25,000 guinea pig protein stimulated plasminogen activator production by cultured bovine capillary endothelial cells in a dose-dependent manner at concentrations of 0.1-10 ng/ml, the same range that was effective for guinea pig and human Mr 18,000 bFGFs. The binding of human 125I-labeled bFGF to baby hamster kidney cells is inhibited equally by the Mr 25,000 guinea pig protein and the Mr 18,000 guinea pig and human bFGFs. Polyclonal antibodies raised against human bFGF recognize both the Mr 25,000 and 18,000 guinea pig proteins in an immunoblot analysis. In a radioimmunoassay, both the Mr 25,000 and Mr 18,000 guinea pig proteins compete equally well with iodinated human bFGF for binding to the anti-human bFGF antibodies. When treated with low concentrations of trypsin, the Mr 25,000 guinea pig bFGF was converted to a Mr 18,000 protein. These results show that the two molecules are closely related and suggest that the Mr 25,000 protein shares substantial homology with the Mr 18,000 bFGF.

Macrophage activation: increased ingestion of IgG-coated erythrocytes after administration of interferon inducers to mice.

In vitro phagocytosis of IgG-opsonized sheep erythrocytes (EA) was used to measure the in vivo activation of mouse peritoneal macrophages. Uptake of EA as enhanced by the extraperitoneal administration of Newcastle disease virus, vesicular stomatitis virus, tilorone or polyinosinic-polycytidylic acid. Ingestion of EA was similarly stimulated by lipopolysaccharide or killed Corynebacterium parvum. Dose-response curves relating concentrations of IgG to phagocytosis were parallel for both treated and control animals. This indicates that the heterogeneity of the macrophage populations did not change and that the overall populations were activated with respect to phagocytic ability. Numbers of macrophages were not increased (except in C. parvum-treated mice), suggesting that resident, rather than newly recruited macrophages, were activated by the different agents.

Selective phagocytic paralysis induced by immobilized immune complexes.

The phagocytic recognition by peritoneal macrophages plated on glass- or plastic-bound immune complexes of bovine plasma albumin (BSA) and anti-BSA was examined. Ingestion but not the attachment of erythrocytes opsonized with an IgG rich antiserum (EA) was markedly inhibited. In contrast, macrophage interactions with complement-coated (EAC) red cells, or ingestion of latex particles, yeast cell walls or glutaraldehyde-treated erythrocytes was not inhibited. Complexes prepared with pepsin-treated anti-BSA IgG were ineffective indicating a requirement for the Fc region. Inhibition of ingestion of EA was not a consequence of macrophage spreading and did not appear to be mediated by solubilized complexes or by cell-derived inhibitors of phagocytosis. Significant restoration of the ability to ingest EA was obtained when macrophages on complex-coated substrates were incubated for 4-8 h in medium enriched with mouse or fetal bovine serum. Restoration was also attained by removing macrophages from complex-coated dishes and replating onto uncoated dishes. The selective inhibition of ingestion of EA may be due to blocking of Fc receptors by the complexes but depletion of receptors by endocytosis of complexes cannot be ruled out. Alternatively, the complexes may have induced selective failure of the interiorization mechanism.