A human monoclonal antibody that binds to CTLA-4, or an antigen-binding fragment thereof, wherein said antibody or fragment competes for binding to CTLA-4 with a reference antibody, wherein the antibody or antigen-binding fragment thereof has the following properties: a) a binding affinity for CTLA-4 of 10 -9 M or greater as determined by BIAcore; b) inhibits binding between CTLA-4 and B7-1 with an IC 50 of 100 nM or lower; and c) inhibits binding between CTLA-4 and B7-2 with an IC 50 of 100 nM or lower, wherein the reference antibody is selected from the group consisting of: i) an antibody comprising a heavy chain that comprises the amino acid sequence of SEQ ID NO: 9 and a light chain that comprises the amino acid sequence of SEQ ID NO: 22; ii) an antibody comprising a heavy chain that comprises the amino acid sequence of SEQ ID NO: 5 and a light chain that comprises the amino acid sequence of SEQ ID NO: 18; iii) an antibody comprising a heavy chain that comprises the amino acid sequence of SEQ ID NO: 1 and a light chain that comprises the amino acid sequence of SEQ ID NO: 14; iv) an antibody comprising a heavy chain that comprises the amino acid sequence of SEQ ID NO: 2 and a light chain that comprises the amino acid sequence of SEQ ID NO: 15; v) an antibody comprising a heavy chain that comprises the amino acid sequence of SEQ ID NO: 8 and a light chain that comprises the amino acid sequence of SEQ ID NO: 21; vi) an antibody comprising a heavy chain that comprises the amino acid sequence of SEQ ID NO: 3 and a light chain that comprises the amino acid sequence of SEQ ID NO: 16; vii) an antibody comprising a heavy chain that comprises the amino acid sequence of SEQ ID NO: 4 and a light chain that comprises the amino acid sequence of SEQ ID NO: 17; viii) an antibody comprising a heavy chain that comprises the amino acid sequence of SEQ ID NO: 10 and a light chain that comprises the amino acid sequence of SEQ ID NO: 23; and ix) an antibody comprising a heavy chain that comprises the amino acid sequence of SEQ ID NO: 11 and a light chain that comprises the amino acid sequence of SEQ ID NO: 24. a) a binding affinity for CTLA-4 of 10 -9 M or greater as determined by BIAcore; b) inhibits binding between CTLA-4 and B7-1 with an IC 50 of 100 nM or lower; and c) inhibits binding between CTLA-4 and B7-2 with an IC 50 of 100 nM or lower, i) an antibody comprising a heavy chain that comprises the amino acid sequence of SEQ ID NO: 9 and a light chain that comprises the amino acid sequence of SEQ ID NO: 22; ii) an antibody comprising a heavy chain that comprises the amino acid sequence of SEQ ID NO: 5 and a light chain that comprises the amino acid sequence of SEQ ID NO: 18; iii) an antibody comprising a heavy chain that comprises the amino acid sequence of SEQ ID NO: 1 and a light chain that comprises the amino acid sequence of SEQ ID NO: 14; iv) an antibody comprising a heavy chain that comprises the amino acid sequence of SEQ ID NO: 2 and a light chain that comprises the amino acid sequence of SEQ ID NO: 15; v) an antibody comprising a heavy chain that comprises the amino acid sequence of SEQ ID NO: 8 and a light chain that comprises the amino acid sequence of SEQ ID NO: 21; vi) an antibody comprising a heavy chain that comprises the amino acid sequence of SEQ ID NO: 3 and a light chain that comprises the amino acid sequence of SEQ ID NO: 16; vii) an antibody comprising a heavy chain that comprises the amino acid sequence of SEQ ID NO: 4 and a light chain that comprises the amino acid sequence of SEQ ID NO: 17; viii) an antibody comprising a heavy chain that comprises the amino acid sequence of SEQ ID NO: 10 and a light chain that comprises the amino acid sequence of SEQ ID NO: 23; and ix) an antibody comprising a heavy chain that comprises the amino acid sequence of SEQ ID NO: 11 and a light chain that comprises the amino acid sequence of SEQ ID NO: 24.