PKCθ is required for alloreactivity and GVHD but not for immune responses toward leukemia and infection in mice
Javier O. Valenzuela, Cristina Iclozan, Mohammad S. Hossain, Martin Prlic, Emily Hopewell, Crystina C. Bronk, Junmei Wang, Esteban Celis, Robert W. Engelman, Bruce R. Blazar, Michael J. Bevan, Edmund K. Waller, Xue-Zhong Yu, Amer A. Beg
Javier O. Valenzuela, Cristina Iclozan, Mohammad S. Hossain, Martin Prlic, Emily Hopewell, Crystina C. Bronk, Junmei Wang, Esteban Celis, Robert W. Engelman, Bruce R. Blazar, Michael J. Bevan, Edmund K. Waller, Xue-Zhong Yu, Amer A. Beg
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Research Article Immunology

PKCθ is required for alloreactivity and GVHD but not for immune responses toward leukemia and infection in mice

Abstract

When used as therapy for hematopoietic malignancies, allogeneic BM transplantation (BMT) relies on the graft-versus-leukemia (GVL) effect to eradicate residual tumor cells through immunologic mechanisms. However, graft-versus-host disease (GVHD), which is initiated by alloreactive donor T cells that recognize mismatched major and/or minor histocompatibility antigens and cause severe damage to hematopoietic and epithelial tissues, is a potentially lethal complication of allogeneic BMT. To enhance the therapeutic potential of BMT, we sought to find therapeutic targets that could inhibit GVHD while preserving GVL and immune responses to infectious agents. We show here that T cell responses triggered in mice by either Listeria monocytogenes or administration of antigen and adjuvant were relatively well preserved in the absence of PKC isoform θ (PKCθ), a key regulator of TCR signaling. In contrast, PKCθ was required for alloreactivity and GVHD induction. Furthermore, absence of PKCθ raised the threshold for T cell activation, which selectively affected alloresponses. Most importantly, PKCθ-deficient T cells retained the ability to respond to virus infection and to induce GVL effect after BMT. These findings suggest PKCθ is a potentially unique therapeutic target required for GVHD induction but not for GVL or protective responses to infectious agents.

Authors

Javier O. Valenzuela, Cristina Iclozan, Mohammad S. Hossain, Martin Prlic, Emily Hopewell, Crystina C. Bronk, Junmei Wang, Esteban Celis, Robert W. Engelman, Bruce R. Blazar, Michael J. Bevan, Edmund K. Waller, Xue-Zhong Yu, Amer A. Beg

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Figure 1

PKCθ is required for efficient proliferation of CD8 T cells in vitro but not in vivo.

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PKCθ is required for efficient proliferation of CD8 T cells in vitro but...
WT and PKCθ–/– OT-1 CD8 T cells were activated in vitro with microspheres bearing H-2Kb:Ig, B7.1:Fc, and 0.1 μM of OVA257–264 (OVAp) (A) or indicated OVA257–264 amounts (B). Cell proliferation (A and B) was measured by 3H-thymidine incorporation. SD within triplicate samples is indicated. For in vivo studies, CFSE-labeled WT and PKCθ–/– OT-1 T cells were transferred into C57BL/6 CD45.1 congenic recipients prior to immunization with 25 μg LPS with or without 10 μg OVA. Cell proliferation (C) and clonal expansion (D) of donor T cells was measured in draining lymph nodes by CFSE dilution. SD within triplicate samples is indicated in D. (E) WT and PKCθ–/– OT-1 T cells were transferred and mice immunized as in C. 3 days later, splenocytes pulsed with OVA257–264 (CFSE 0.25 μM) or left unpulsed (CFSE 2.5 μM) were injected and monitored 10–12 hours later in the spleen by FACS. The T cell response to the OVA-expressing L. monocytogenes (LM-OVA) was measured by immunizing mice i.v. with 2 × 103 CFUs. 7 days later, clonal expansion (F) and intracellular expression of IL-2 and IFN-γ (G) of activated OVA-specific CD8 T cells were measured in spleens by staining for CD8, CD44, Kb/OVA tetramer (F), and CD8, IL-2, and IFN-γ after a 4-hour in vitro restimulation with 100 nM OVA257–264 in the presence of brefeldin A (G) followed by FACS. Numbers in F and G represent percentages within spleen CD8 T cells.