Common Gamma Chain Cytokines Contribute To Acute GvHD Via Perforin/Granzyme B-Mediated Cytotoxicity Of CD8 T Cells

Allogeneic hematopoietic cell transplantation (allo-HCT) is an important treatment option for different hematological malignancies, but also for some nonmalignant hematological disorders such as sickle cell anemia, aplastic anemia or thalassemia(1). In the ladder group the graft-versus-leukemia (GvL) effect mediated by donor T cells is less important and prevention of graft-versus-host disease (GvHD), which occurs in 40-50% of allo-HCT patients, is a major priority. The common gamma chain (CD132) is a cytokine receptor sub-unit that is common to the interleukin (IL) receptors of IL-2, IL-4, IL-7, IL-9, IL-15 and IL-21. Since several of these cytokines were shown to be increased in the serum of patients developing acute GvHD, we reasoned that inhibition of CD132 could have a profound effect on acute GvHD by inhibiting the bioactivity of multiple proinflammatory cytokines.

We observed that anti-CD132 treatment reduced GvHD potently with respect to survival, production of TNF, IFN-γ, IL-6, MCP-1 and GvHD histopathology. Protection was only seen when anti-CD132 was applied in a CD8 T cell-dependent GvHD model while no protection was seen when only CD4 T cells were given. Mechanistically, we could show that CD8 T cells isolated from mice treated with anti-CD132 had reduced levels of Granzyme B and that GvHD induced by Perforin-deficient T cells was resistant towards blockade by anti-CD132 treatment. These data indicated a role of the common gamma chain cytokines for the induction of Perforin/Granzyme B in CD8 T cells during GvHD. Compatible with this notion, exposure of CD8 T cells towards IL-2, IL-7, IL-15 and IL-21 alone or in combination induced increased levels of Granzyme B.

Based on these findings, we concluded that CD8 T cells that are activated by common gamma chain cytokines during GvHD produce then Granzyme B which can be blocked by anti-CD132 treatment. This therapeutic approach has particular clinical potential for patients undergoing allogeneic transplantation for nonmalignant indications, since graft-versus-tumor activity is not required.