Although CD4 ؉ CD25 ؉ T cells (T regulatory cells [Tregs]) and natural killer T cells (NKT cells) each protect against graftversus-host disease (GVHD), interactionsbetween these 2 regulatory cell populations after allogeneic bone marrow transplantation (BMT) have not been studied. We show that host NKT cells can induce an in vivo expansion of donor Tregs that prevents lethal GVHD in mice after conditioning with fractionated lymphoid irradiation (TLI) and anti-T-cell antibodies, a regimen that models human GVHDprotective nonmyeloablative protocols using TLI and antithymocyte globulin (ATG), followed by allogeneic hematopoietic cell transplantation (HCT). GVHD protection was lost in NKT-cell-deficient J␣18 ؊/؊ hosts and interleukin-4 (IL-4) ؊
IntroductionGraft-versus-host disease (GVHD), a major complication of allogeneic bone marrow transplantation, causes injury to the host intestines, skin, and liver, [1][2][3][4] and is mediated by donor conventional CD4 ϩ and CD8 ϩ T cells. 2,5 Both natural killer T cells (NKT cells) 6-8 and CD4 ϩ CD25 ϩ T regulatory cells (Tregs) 9-11 can regulate GVHD without prior exposure to the target antigens. [6][7][8][9][10][11][12][13][14][15][16] Host NKT cells express an invariant V␣14J␣18 T-cell receptor (TCR)␣ chain, and secrete large amounts of interleukin (IL)-4 and/or interferon (IFN)-␥ within hours after activation via TCR recognition of the nonpolymorphic CD1d antigen-presenting molecule. 13,[17][18][19][20][21] Host or donor NKT cell-mediated GVHD protection has been reported to be dependent on NKT cell secretion of cytokines, which induce T helper (Th) 2 polarization of conventional T cells, 8,22 and thereby attenuate their capacity to induce GVHD. 8,12,13,[23][24][25][26][27] Naturally occurring CD4 ϩ CD25 ϩ Tregs of either host or donor origin can protect against GVHD by suppressing the function of donor conventional T cells through direct cell contact [28][29][30][31][32][33] or secretion of cytokines, including 32,34 In nontransplant settings, activation of NKT cells using ␣-galactosyl ceramide, a marine sponge-derived glycolipid, can activate Tregs via NKT-cell secretion of IL-2. 35,36 We investigated whether host NKT cells can interact synergistically with donor Tregs to protect against GVHD after bone marrow transplantation. Hosts were conditioned with total lymphoid irradiation (TLI) and antithymocyte serum (ATS), a regimen that protects mice against lethal GVHD that has been successfully applied to hematopoietic cell transplantation in humans to achieve a low incidence of acute GVHD. 37,38 Our results demonstrate the novel finding that host NKT cells and donor Tregs interact to prevent conventional donor T cells from expanding and inducing lethal GVHD. Proliferation of donor Tregs in vivo occurred after transplantation and was dependent on host NKT cell secretion of IL-4.
Methods MiceWild-type (BALB/cJ and BALB/cByJ) and IL-4 Ϫ/Ϫ male BALB/c (H-2 d ) male mice, 8 to 10 weeks old, were obtained from The Jackson Laboratory (Bar Harbor, ME) and the Department of Com...