Two Distinct Porcine Natural Killer Lytic Trigger Molecules as PNK-E/G7 Molecular Complex

PNK-E and G7 mAbs regulate porcine NK and ADCC activities by binding to distinct NK function-associated trigger molecules on porcine NK cells. Previous work demonstrates that PNK-E mAb binds to a 205-kDa tetrameric molecule composed of two 47-kDa peptides and two 50-kDa peptides and G7 mAb binds to a distinct 40-kDa heterodispersed monomeric peptide on porcine NK cells. The data presented herein demonstrate that all PNK-E4 PBLs are G71 and all G71 PBLs are PNK-E4 indicating that the PNK-E and G7 molecules are coexpressed by porcine NK cells. Bound G7 mAb blocks subsequent binding of PNK-E mAb but not the converse. Bound F(ab′)2 G7 mAb abrogates the ability of whole PNK-E mAb to enhance NK activity but bound F(ab′)2 PNK-E mAb has no affect on G7 mAb enhancement of NK activity. PNK-E mAb enhanced NK activity is inhibited by binding of F(ab′)2 G7 mAb even though whole PNK-E mAb remains bound. However, bound F(ab′)2 PNK-E mAb has no affect on G7 mAb-enhanced NK activity. When PNK-E and G7 mAbs were tested alone and together in NK assays, comparable levels of enhancement were observed. PNK-E and G7 hybridomas express surface mAb through which NK cells bind and specifically lyse these hybridomas. Lysis of PNK-E and G7 hybridomas is inhibited by pretreatment of PBLs with F(ab′)2 G7 mAb. These data indicate a physical association between the PNK-E and G7 molecules on NK cells and suggest that the G7 molecule is external to the PNK-E molecule.