Identification and characterization of an alternative cytotoxic T lymphocyte-associated protein 4 binding molecule on B cells.
To determine whether alternative cytotoxic T lymphocyte-associated protein 4 (CTLA4) binding proteins exist on B cells, we constructed (i) mCTLA4hIgG consisting of the extracellular region of a mouse CTLA4 molecule and the Fc portion of a human IgG1 molecule and (ii) PYAAhIgG, a mutant mCTLA4hIgG, having two amino acid substitutions on the conserved MYPPPY motif in the complementarity-determining region 3-like region and lacking detectable binding to both B7-1 and B7-2 molecules. Using these fusion proteins (mCTLA4hIgG and PYAAhIgG), we demonstrated that a mouse immature B-cell line, WEHI231 cells, expressed alternative CTLA4 binding molecules (ACBMs) that were distinct from both B7-1 and B7-2. ACBMs were 130-kDa disulfide-linked proteins. More importantly, ACBMs were able to provide costimulatory signal for T-cell proliferation in the presence of anti-CD3 monoclonal antibodies. In addition, we demonstrated that more than 20% of B220+ cells obtained from normal mouse spleen expressed ACBMs.
Murakami
M
M
Section of Immunopathogenesis, Institute of Immunological Science, Hokkaido University, Sapparo, Japan.
Takahashi
Y
Y
Isashi
Y
Y
Kon
S
S
Jia
W Y
WY
Inobe
M
M
Abe
R
R
Uede
T
T
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal; D001402:B-Lymphocytes / Q000276:immunology*; D001483:Base Sequence; D017252:CD3 Complex / Q000276:immunology / Q000502:physiology; D016466:CHO Cells; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D017124:Conserved Sequence; D006224:Cricetinae; D017931:DNA Primers; D005434:Flow Cytometry; D006801:Humans; D007141:Immunoglobulin Fc Fragments / Q000096:biosynthesis / Q000276:immunology; D007074:Immunoglobulin G / Q000096:biosynthesis / Q000276:immunology; D008213:Lymphocyte Activation; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D016133:Polymerase Chain Reaction; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000276:immunology; D013154:Spleen / Q000276:immunology; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D014162:Transfection
D000911:Antibodies, Monoclonal; D017252:CD3 Complex; D002352:Carrier Proteins; D017931:DNA Primers; D007141:Immunoglobulin Fc Fragments; D007074:Immunoglobulin G; D011993:Recombinant Fusion Proteins