4-1BB T-cell antigen binds to mature B cells and macrophages, and costimulates anti-mu-primed splenic B cells.
4-1BB is expressed on activated murine T cells and may function as an accessory signaling molecule during T-cell activation. To identify putative 4-1BB ligands, a fusion protein consisting of the extracellular domain of 4-1BB fused to human placental alkaline phosphatase (4-1BB-AP) was constructed. Alkaline phosphatase activity could then be used as an indicator of the relative amount of bound 4-1BB. These studies indicated that 4-1BB-AP specifically bound to the surface of various mature B and macrophage cell lines. 4-1BB-AP bound at low levels to T cell lines (non-activated and anti-CD3-activated), pre-B-cell lines, and an immature macrophage cell line. 4-1BB-AP did not bind to a glial tumor cell line, HeLa cells, or COS cells. In addition, 4-1BB-AP bound at higher levels to F(ab')2 anti-mu-activated primary B cells compared to anti-CD3-activated primary T cells. Scatchard analysis indicated that the A20 B cell lymphoma expressed 3680 binding sites per cell with a Kd of 1.86 nM. Affinity cross-linking studies demonstrated that a major cell surface species of 120 kDa bound to 4-1BB-AP; 4-1BB-AP also bound to a minor species of approximately 60 kDa. The addition of paraformaldehyde-fixed SF21 cells expressing recombinant 4-1BB synergized with F(ab')2 anti-mu in inducing splenic B cell proliferation suggesting that 4-1BB may function as a regulator of B cell growth.
Pollok
K E
KE
Indiana University School of Medicine, Indianapolis 46202.
Kim
Y J
YJ
Hurtado
J
J
Zhou
Z
Z
Kim
K K
KK
Kwon
B S
BS
D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology*; D015703:Antigens, CD; D001402:B-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D002450:Cell Communication; D005260:Female; D008024:Ligands; D008213:Lymphocyte Activation; D008211:Lymphocyte Cooperation; D008264:Macrophages / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D017475:Receptors, Nerve Growth Factor / Q000378:metabolism; D018124:Receptors, Tumor Necrosis Factor; D011993:Recombinant Fusion Proteins; D013154:Spleen / Q000166:cytology; D013601:T-Lymphocytes / Q000276:immunology*; D053261:Tumor Necrosis Factor Receptor Superfamily, Member 9
D015703:Antigens, CD; D008024:Ligands; D017475:Receptors, Nerve Growth Factor; D018124:Receptors, Tumor Necrosis Factor; D011993:Recombinant Fusion Proteins; C505714:TNFRSF9 protein, human; C505715:Tnfrsf9 protein, mouse; D053261:Tumor Necrosis Factor Receptor Superfamily, Member 9