Efficient expansion of regulatory T cells in vitro and in vivo with a CD28 superagonist

Abstract

CD4 + CD25 + T cells play a central role in the suppression of autoimmunity and inflammation, making their in vivo expansion a highly attractive therapeutic target. By phenotyping with a novel rat CTL antigen-4 (CTLA-4)-specific monoclonal antibody (mAb) and functional in vitro assays, we here first establish that rat CD4 + CD25 + T cells correspond to the regulatory T cells (Treg cells) described in mice and humans: they constitutively express CTLA-4, produce IL-10 but not IL-2, and are able to suppress the proliferation of costimulated CD25-negative indicator cells. Furthermore, we show that rat Treg cells respond less well than CD25 -T cells to conventional costimulation, but are readily expanded in vitro with "superagonistic" CD28-specific mAb which are potent mitogens for all T cells without the need for TCR engagement. In vivo, functional Treg cells are preferentially expanded by CD28 stimulation over other T cell subsets, leading to a 20-fold increase within 3 days in response to a single antibody dose. These data suggest that CD28-driven activation of Treg cells may be highly effective in the treatment of inflammatory and autoimmune diseases.

Selective expansion of memory CD4+ T cells by mitogenic human CD28 generates inflammatory cytokines and regulatory T cells

“…4). This is in contrast to an in vitro study using mitogenic CD28 JJ316 [8,18], which reported a four-fold greater expansion of Treg than effector CD4 Tcells. A major criticism of that study is that CTLA-4 rather than FOXP3 was used to identify Treg.…”

“…A major criticism of that study is that CTLA-4 rather than FOXP3 was used to identify Treg. Lin et al [18] and Beyersdorf et al [7] stated that mitogenic CD28 expanded purified regulatory T cells. However, in those studies, bead-purified CD4 + CD25…”

“…Treg are normally unresponsive using conventional CD3 and CD28 antibody stimulation and do not proliferate. However, in those studies reporting expansion of regulatory T cells by JJ316, the purity of the starting cells was not well defined [7,18] (Fig. 1A).…”

The 4-1BB Costimulation Augments the Proliferation of CD4+CD25+ Regulatory T Cells

“…These results indicate that 4-1BB costimulation can increase the production of IFN-␥ and TNF-␣, but not IL-2, in CD4 ϩ CD25 ϩ T cells. This finding is consistent with the general observation that CD4 ϩ CD25 ϩ regulatory T cells, including those expanded under anti-CD28 costimulation (31,32), do not produce IL-2 (reviewed in Ref. 2).…”

An immunomodulatory role for CD4+CD25+ regulatory T lymphocytes in hepatitis C virus infection

“…28 Lin et al found that the response of regulatory T cells to conventional costimulation was ineffective in comparison with conventional T cells, but readily expanded in vitro with "superagonistic" CD28-specific monoclonal antibody without the need for T cell receptor engagement. 29 Therefore, costimulatory receptors CD28 and CD27 expression on CD4 ϩ CD25 ϩ regulatory T cells is probably not a reflection of function as observed on general CD4 ϩ T cells. Most of the CD4 ϩ CD25 ϩ T cells express the CD45RO isoform, which is characteristic of memory T cells, and few express CD45RA, a marker for naïve T cells.…”