Granzyme Expression and Function in Effector and Regulatory T cells

Abstract

The perforin/granzyme pathway is a central component of anti-tumor and antiviral effector immune responses mediated by cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells. However, little is known about the conditions under which granzymes, in particular granzyme C, is expressed in discrete T and NK cell subsets. Thus, we generated a granzyme C-specific monoclonal antibody and used flow cytometry to characterize its expression at single-cell resolution in lymphocytes that were derived from either wild-type mice or granzyme B-deficient mice that have a small deletion within the proximal portion of the granzyme B gene. These studies revealed that deletion of this region perturbs granzyme expression, which results in earlier and more abundant expression of granzyme C in both T and NK cells, suggesting that regulatory elements within the deleted region are important for controlling the expression of granzyme C. In addition to effector lymphocytes, we previously demonstrated that granzymes are expressed in in vitro-activated human and tumor-activated murine regulatory T (Treg) cells. Although no granzyme C was detected in murine Treg cells, we observed granzyme B expression in Treg cells alloactivated in mixed lymphocyte reactions, in a model of graft-versus-host disease (GvHD), and in an allogeneic tumor challenge model. However, wild-type and granzyme B-deficient Treg cells were equally able to suppress effector T (Teff) cell proliferation driven by multiple stimuli, including allogeneic antigen-presenting cells. Adoptive transfer of granzyme B-deficient Treg cells prevented GvHD lethality and suppressed GvHD-associated serum cytokine production in vivo. These data suggesting that granzyme B is not required for Treg cell function in the setting of allogeneic mismatch are in contrast with our previous findings demonstrating that granzyme B plays a non-redundant role in Treg cell-mediated suppression of anti-tumor responses. Gene expression profiling of purified Treg cells revealed broad changes in the molecular signatures of naïve, tumor-activated, and GvHD-activated Treg cells, suggesting that cell-intrinsic differences during Treg cell activation may partially account for the differential phenotypes observed in these models. Finally, these findings also suggest that targeting discrete Treg cell suppressive mechanisms may be therapeutically beneficial in segregating GvHD and graft-versus-tumor immune responses

Committee Chair

Timothy Ley

Committee Members

John Atkinson, Marco Colonna, Ted Hansen, Chyi-Song Hsieh, John Russell

Comments

Permanent URL: https://doi.org/10.7936/K79Z92TP

Degree

Doctor of Philosophy (PhD)

Author's Department

Biology & Biomedical Sciences (Immunology)

Author's School

Graduate School of Arts and Sciences

Document Type

Dissertation

Date of Award

Spring 5-15-2011

Language

English (en)

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