Compositions and methods for regulating NK cell activity

1. A method of producing an antibody which cross-reacts with multiple human KIR2DL polypeptides and which neutralizes the inhibitory activity of such polypeptides, said method comprising the steps of:

(a) immunizing a non-human mammal with an immunogen comprising an immunogenic extracellular portion of a human KIR2DL polypeptide;

(b) preparing antibodies from said immunized mammal, wherein said antibodies bind said human KIR2DL polypeptide;

(c) selecting antibodies of (b) that cross-react with at least two different human KIR2DL polypeptides that each recognizes a different group of HLA-C class I allotypes; and

(d) selecting antibodies of (c) that potentiate NK cell activity.

2. The method of claim 1 , which further includes (e) selecting and isolating an antibody from the antibodies of (d) that binds a NK cell or KIR2DL polypeptide of a primate.

3. The method according to claim 1 , wherein said antibody competes with the DF-200 antibody (deposited as CNCM I-3224) for binding to said KIR polypeptide.

4. The method of claim 1 , wherein the order of steps (c) and (d) is optionally reversed.

5. The method of claim 1 , further comprising the step of preparing a chimeric, or humanized antibody from the selected antibody which cross-reacts with at least two different human KIR2DL polypeptides that each recognizes a different group of HLA-C class I allotypes.

6. The method of claim 1 , further comprising the step of preparing an antibody fragment which cross-reacts with at least two different human KIR2DL polypeptides that each recognizes a different group of HLA-C class I allotypes.

7. The method of claim 6 , wherein the antibody fragment is a Fab, Fab′, Fab′-SH, F(ab′)2, Fv, diabody, single-chain antibody fragment, or a multi-specific antibody comprising a number of different antibody fragments.

8. The method of claim 1 , wherein the at least two different human KIR2DL polypeptides of step (c) comprise KIR2DL1, KIR2DL2, and/or KIR2DL3.

9. The method of claim 1 , wherein the antibody prepared in step (b) is a monoclonal antibody.

10. The method of claim 1 , wherein the antibodies selected in step (d) cause an at least about 50% potentiation in NK cytotoxicity, as measured by a chromium release test of cytotoxicity.

11. The method of claim 1 , wherein the antibody binds to substantially the same epitope as the DF-200 antibody (deposited as CNCM I-3224).

12. The method of claim 1 , wherein the antibody selected in step (b) inhibits the binding of a HLA-c allele molecule having a Lys residue at position 80 to a human KIR2DL1 receptor, and the binding of a HLA-C allele molecule having an Asn residue at position 80 to human KIR2DL2/3 receptors.

13. The method of claim 1 , wherein the human KIR2DL polypeptide comprises at least one extracellular Ig domain of the KIR2DL receptor.

14. The method of claim 1 , wherein the human KIR2DL polypeptide comprises both extracellular IgG domains of the KIR2DL receptor.