No abstract

Human IgM molecules were treated with Na(2)SO(3) or mercaptoethylamine in concentrations ranging from 2 to 14mm or 2 to 22mm respectively. The dissociation of IgM to IgM(s) varied from 0% to 100%. At the intermediate concentrations of either reagent the amount of freed J chains was less than expected. In an attempt to find an explanation for this, IgM was partially dissociated to IgM(s) with mercaptoethylamine. The IgM(s) isolated by gel filtration was divided according to the ascending and descending portions of the elution curve. These portions were treated with 24mm-mercaptoethylamine and analysed for the presence of J chains. Only the ascending portion contained free J chains. Thus, after mild reduction where not all the IgM molecules are dissociated to IgM(s), some J chains remain covalently attached to some IgM(s) molecules although most of the J chains are freed. It was concluded that the J chain could serve as a ;hitch' for IgM(s) molecules forming intact IgM.

The effect of selected monosaccharides on the random migration of normal adult rabbit alveolar macrophages (AM) was investigated. It was observed that 10 mM of L-fucose, L-galactose, or D-mannose stimulated AM migration 1.5-2.0 times. In addition, derivatives of L-fucose and D-mannose occupying the carbon-6 position such as L-fucosyl-lactose, D-mannose-6-phosphate, D-mannitol, and mannan enhanced the migration of AM, whereas derivatives of L-fucose and D-mannose in the carbon-1 position produced no migration enhancement. Macrophage migration enhancement activity that was produced spontaneously by spleen cell cultures from normal young rabbits was destroyed by treatment with L-fucosidase. Accordingly, the migration enhancement factor (MEF) found in spleen cell culture supernatants appeared to depend on L-fucose conjugated to some protein carrier because MEF was non-dialyzable. When normal adult AM were treated with L-fucosidase, they lost their responsiveness to migration inhibitory factor (MIF) but retained their responsiveness to MEF. We have interpreted this to mean that the MIF and MEF receptors are distinct. Synthetic MEFs were prepared by conjugating L-fucose, D-mannose, of L-galactose to bovine serum albumin (BSA). It was noted that these sugar-BSA conjugates were about 200 times more effective than the corresponding free sugars in producing migration enhancement. In addition, these sugar-BSA conjugates neutralized MIF activity in a migration inhibition test.