Five different Ag-binding suppressor factors from two types of hapten-specific Ts cell hybridomas (TsF1 inducer and TsF3 effector factors) were bound by an anti-lipomodulin mAb (141-B9), that crossreacts with rodent glycosylation inhibition factor (GIF). The Ag-specific suppressor activity in these hybridoma supernatants was bound by anti-lipomodulin columns and could be recovered by elution at acid pH. Additional evidence for the expression of lipomodulin/GIF activity on these TsF molecules was demonstrated by the ability of the eluted fractions to inhibit the glycosylation of IgE-binding peptides during their biosynthesis. The same biologic activity is associated with GIF and lipomodulin. The relationship between TsF and lipomodulin/GIF was confirmed in a serologic assay, which showed that TsF1 and TsF3 molecules, whether purified over Ag, anti-IJ or anti-TsF columns, are recognized by the mAb. 141-B9. The combined results indicate that Ag-binding Ts factors share a common antigenic determinant with phospholipase inhibitory proteins such as lipomodulin and GIF. In addition, the demonstration of glycosylation regulatory activity carried on these TsF molecules suggests a possible mode for their bioactivity.