Appeal No. 1999-2330
Application No. 08/219,200
inhibiting T cell proliferation. According to the specification, page 12, ?useful in the
method of the invention is a B7Ig fusion protein that comprises a polypeptide
corresponding to the extracellular domain of the B7 antigen and an immunoglobulin
constant region that alters the solubility, affinity and/or valency (valency is herein
defined as the number of binding sites available per molecule) of the B7 antigen.”
Administration of B7 antigen, e.g., as a soluble B7Ig fusion protein to react with CD28
positive T cells, will bind the CD28 receptor on the T cells and result in inhibition of the
functional responses of T cells. Specification, page 21.
Under conditions where T cell interactions are occurring as a result of contact
between T cells and B cells, binding of introduced B7 antigen in the form of a fusion
protein that binds to CD28 receptor on CD28 positive T cells should interfere, i.e.,
inhibit, the T cell interactions with B cells. Likewise, administration of the CD28 antigen,
or its fragments or derivatives, in vivo, for example in the form of a soluble CD28Ig
fusion protein, will result in binding of the soluble CD28 Ig to B7 antigen, preventing the
endogenous stimulation of CD28 receptor by B7 positive cells, such as activated B
cells, and interfering with the interaction of B7 positive cells with T cells. Id.
In addition, the B7 fusion proteins may be used to regulate T cell proliferation.
For example, the soluble CD28Ig and B7Ig fusion proteins may be used to block T cell
proliferation in graft versus host (GVH) disease which accompanies allogenic bone
marrow transplantation. Thus the B7 antigen in the form of B7Ig fusion protein, or in
combination with immunosuppressants such as cyclosporin, may be used for blocking
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