Macrophage aggregation factor: some properties.

The lymphokine activity, macrophage aggregation factor (MAgF) has been investigated further. Activity was consistently found in 24 hr test, but not control, spleen cell culture supernatants. This was higher after dialysis against water, than in the original culture supernatants. MAgF was heat-stable, inactivated by alpha-chymotrypsin, partially inactivated by trypsin and not affected by neuraminidase. Activity was recovered from the supernatant after protein precipitation with 1 M perchloric acid, leading to a modest purification. Activity was only marginally reduced after treatment with periodate, and was not absorbed by Concanavalin A-Sepharose. Polyacrylamide gel electrophoresis showed that MAgF migrated cathodally to albumin. Aggregation, as measured in a batch centrifugation assay, was an expression both of cell-substrate and cell--cell adhesion.