Ligating BDCA-2 protein with BDCA-2 specific antibody for detecting or modulating dendritic cells

1. A method of detecting BDCA-2 protein in a biological sample, comprising:

a) combining the sample with a monoclonal, synthetic, or recombinant antibody or antigen binding fragment under conditions where the antibody or fragment will bind to BDCA-2 protein in the sample to form a complex, and

b) detecting complex formed in step (a);

wherein said antibody or antigen-binding fragment comprises a polypeptide domain that specifically binds a BDCA-2 protein encoded by SEQ ID NO:1;

wherein the BDCA-2 protein is encoded by exons 1-6; exons 1 and 3-6; exons 1-2 and 4-6; or exons 1-3 and 5-6 of SEQ ID NO:1.

2. The method of claim 1 , wherein the BDCA-2 protein is displayed on the surface of a dendritic cell.

3. The method of claim 2 , wherein the step of detecting the complex comprises detecting functional modulation of the dendritic cell resulting from binding an antibody or antigen binding fragment to BDCA-2 protein on the cell in step (a).

4. The method of claim 2 , wherein the step of detecting the complex comprises detection of one or more of the following:

down-regulation of type I interferon production,

down-regulation of Th1 immune responses,

induction of intracellular Ca ++ mobilization, and/or

polarization of an immune response to Th2.

5. A method of ligating BDCA-2 protein on a dendritic cell, comprising:

contacting the cell with an antibody or antigen-binding fragment under conditions where the antibody or antigen-binding fragment will ligate to BDCA-2 protein on the dendritic cell;

wherein said antibody or antigen-binding fragment comprises a polypeptide domain that specifically binds a BDCA-2 protein encoded by SEQ ID NO:1;

wherein the BDCA-2 protein is encoded by exons 1-6; exons 1 and 3-6; exons 1-2 and 4-6; or exons 1-3 and 5-6 of SEQ ID NO:1.

6. The method of claim 5 , wherein ligation of BDCA-2 antigen on the dendritic cell results in a metabolic change selected from:

down-regulation of type I interferon production,

down-regulation of Th1 immune responses,

induction of intracellular Ca ++ mobilization, and

polarization of an immune response to Th2.

7. The method of claim 1 , wherein the sample comprises cells, and step (b) comprises separating cells to which the antibody or fragment has bound.

8. The method of claim 1 , wherein:

the conditions in step (a) comprise including a test agent with the antibody or antigen binding fragment; and

step (b) comprises detecting complex formed in step (a) in the presence of the test agent.

9. The method of claim 3 , wherein the functional modulation is detected as an induction of CD4 + cell responses.

10. The method of claim 3 , wherein the functional modulation is detected as an induction of CD8 + cell responses.

11. The method of claim 3 , wherein the functional modulation is detected as a down-regulation of CD4 + cell responses.

12. The method of claim 3 , wherein the functional modulation is detected as a down-regulation of CD8 + cell responses.

13. The method of claim 3 , wherein the functional modulation is detected as a polarization of the immune response towards tolerance and immunity.

14. The method of claim 3 , wherein the functional modulation is detected as a polarization of the CD4 + T cell responses towards Th1 cell development.

15. The method of claim 3 , wherein the functional modulation is detected as a polarization of the CD4+ T cell responses towards Th2 cell development.

16. The method of claim 3 , wherein the functional modulation is detected as a polarization of the CD4+ T cell responses towards Th3/T-regulatory-I CD4+ T cell development.

17. The method of claim 3 , wherein the functional modulation is detected as a functional modulation of B cells.

18. The method of claim 3 , wherein the functional modulation is detected as a functional modulation of NK cells.