Characterization of surface lymphotoxin forms. Use of specific monoclonal antibodies and soluble receptors.
Lymphotoxin (LT) is a cytokine related to TNF, found in human systems in both secreted and membrane bound forms. The well characterized secreted form is a trimer of a single protein, LT-alpha, whereas the surface form is composed of a complex between two related molecules, LT-alpha and LT-beta. Because there is a distinct receptor for the complex, the membrane form is believed to signal via events different from those elicited by TNF and secreted LT-alpha. By using a battery of anti-LT-alpha and LT-beta mAbs, it is clear that two LT surface forms exist on the surface of PMA-activated II-23 cells, a human T cell hybridoma. Assuming that these surface forms are trimers, a minor form appears early after induction having an apparent stoichiometry of LT-alpha 2/beta 1 and is recognized by one group of anti-LT-alpha mAbs and the p55-TNF receptor. The second and predominant form has an apparent LT-alpha 1/beta 2 composition and is recognized by a second group of pantrophic anti-LT-alpha mAbs and the LT-beta receptor. Neither of the heteromeric forms nor a putative LT-beta homotrimeric form were found to be secreted. The properties of surface LT on the II-23 cell system were similar to those of the surface LT forms on Chinese hamster ovary cells transfected with both LT-alpha and LT-beta genes and a number of lymphoid tumor lines. These experiments point toward the LT-alpha 1/beta 2 complex as the predominant membrane form of LT on the lymphocyte surface, and this complex is the primary ligand for the LT-beta receptor.
Browning
J L
JL
Department of Immunology and Inflammation, Biogen, Cambridge, MA 02142.
Dougas
I
I
Ngam-ek
A
A
Bourdon
P R
PR
Ehrenfels
B N
BN
Miatkowski
K
K
Zafari
M
M
Yampaglia
A M
AM
Lawton
P
P
Meier
W
W
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D001483:Base Sequence; D016466:CHO Cells; D002522:Chlorocebus aethiops; D006224:Cricetinae; D005455:Fluorescent Antibody Technique; D006031:Glycosylation; D006801:Humans; D006825:Hybridomas / Q000276:immunology; D007700:Kinetics; D008213:Lymphocyte Activation; D053259:Lymphotoxin beta Receptor; D008233:Lymphotoxin-alpha / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism; D053308:Lymphotoxin-beta; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000276:immunology* / Q000378:metabolism; D008969:Molecular Sequence Data; D011233:Precipitin Tests; D011485:Protein Binding; D011487:Protein Conformation; D011499:Protein Processing, Post-Translational; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000276:immunology; D015398:Signal Transduction; D012995:Solubility; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection; D014407:Tumor Cells, Cultured
D000911:Antibodies, Monoclonal; C505886:LTB protein, human; C505697:LTBR protein, human; D053259:Lymphotoxin beta Receptor; D008233:Lymphotoxin-alpha; D053308:Lymphotoxin-beta; D046911:Macromolecular Substances; D008565:Membrane Proteins; D018124:Receptors, Tumor Necrosis Factor; D011993:Recombinant Fusion Proteins; D013755:Tetradecanoylphorbol Acetate