Methods and compositions for modulating T helper (Th) cell development and function

1. A method for inhibiting or reducing differentiation of a Th precursor (Thp) cell or cell population into a Th2 cell or cell population, comprising contacting said Thp cell or cell population from a subject or sample of interest with an antagonist of IL-21 or IL-21R in an amount sufficient to inhibit or reduce the differentiation, wherein the inhibition or reduction of the differentiation is measured by comparing the level of Th2 cells in the contacted cell or cell population from the subject or sample of interest to the level of Th2 cells in a control subject or sample, and wherein the antagonist is selected from the group consisting of an anti-IL-21R antibody, an antigen-binding fragment of an anti-IL-21R antibody and a soluble IL-21R, wherein the soluble IL-21R comprises an extracellular domain of an IL-21R that is capable of binding IL-21 or a fragment thereof, and wherein the extracellular domain of the soluble IL-21R is at least 90% identical to amino acids 20-235 of SEQ ID NO:4.

2. A method for increasing interferon gamma (IFNγ) levels in a T cell or cell population, comprising contacting said T cell or cell population from a subject or sample of interest with an antagonist of IL-21 or IL-21R in an amount sufficient to increase IFNγ levels in said T cell or cell population, wherein the increase in IFNγ levels is measured by comparing the level of IFNγ in the T cell or cell population from the subject or sample of interest to the level of IFNγ in a T cell or cell population from a control subject or sample, and wherein the antagonist is selected from the group consisting of an anti-IL-21R antibody, an antigen-binding fragment of an anti-IL-21R antibody and a soluble IL-21R, wherein the soluble IL-21R comprises an extracellular domain of an IL-21R that is capable of binding IL-21 or a fragment thereof, and wherein the extracellular domain of the soluble IL-21R is at least 90% identical to amino acids 20-235 of SEQ ID NO:4.

3. The method of either claim 1 or 2 , wherein the antagonist of IL-21 or IL-21 R is a soluble IL-21R, and wherein the extracellular domain of the soluble IL-21R comprises amino acids 1 to 235 of SEQ ID NO:4 or amino acids 20 to 235 of SEQ ID NO:4.

4. The method of claim 3 , wherein the soluble IL-21R further comprises an Fc fragment.

5. The method of either claim 1 or 2 , wherein the antagonist is an anti-IL-21R antibody or an antigen-binding fragment thereof.

6. The method of claim 2 , wherein the T cell or cell population comprises at least one Th1 cell.

7. The method of either claim 1 or 2 , wherein the contacting step is carried out ex vivo, in vitro or in vivo.

8. The method of claim 7 , wherein the contacting step is carried out in a mammalian subject.

9. The method of claim 8 , wherein the mammalian subject is a human.

10. A method for inhibiting or reducing the differentiation of a Thp cell or cell population into a Th2 cell or cell population in a subject in need thereof, comprising administering to the subject an antagonist of IL-21 or IL-21R selected from the group consisting of an anti-IL-21R antibody, an antigen-binding fragment of an anti-IL-21R antibody and a soluble IL-21R, wherein the soluble IL-21R comprises an extracellular domain of an IL-21R that is capable of binding IL-21 or a fragment thereof, and wherein the extracellular domain of the soluble IL-21R is at least 90% identical to amino acids 20-235 of SEQ ID NO:4.

11. A method for increasing interferon gamma (IFNγ) levels in a T cell or cell population in a subject in need thereof, comprising administering to the subject an antagonist of IL-21 or IL-21R selected from the group consisting of an anti-IL-21R antibody, an antigen-binding fragment of an anti-IL-21R antibody and a soluble IL-21R, wherein the soluble IL-21R comprises an extracellular domain of an IL-21R that is capable of binding IL-21 or a fragment thereof, and wherein the extracellular domain of the soluble IL-21R is at least 90% identical to amino acids 20-235 of SEQ ID NO:4.