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Identification and Characterization of an Alternative Cytotoxic T Lymphocyte-Associated Protein 4 Binding Molecule on B Cells

Masaaki Murakami, Yohko Takahashi, Yasuhiro Isashi, Shigeyuki Kon, Wen-Yi Jia, Manabu Inobe, Ryo Abe and Toshimitsu Uede
Proceedings of the National Academy of Sciences of the United States of America
Vol. 93, No. 15 (Jul. 23, 1996), pp. 7838-7842
Stable URL: http://www.jstor.org/stable/40123
Page Count: 5
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Identification and Characterization of an Alternative Cytotoxic T Lymphocyte-Associated Protein 4 Binding Molecule on B Cells
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Abstract

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.

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