InVivoMAb anti-rat CTLA-4 (CD152)

InVivoMAb anti-rat CTLA-4 (CD152) (CLONE: WKH203)

Takatsuka N, Hasegawa A, Takamori A, Shimizu Y, Kato H, Ohashi T, Amagasa T, Masuda T, Kannagi M (2009). "Induction of IL-10- and IFN-gamma-producing T-cell responses by autoreactive T-cells expressing human T-cell leukemia virus type I Tax" Int Immunol 21(9):1089-100. PubMed

Human T-cell leukemia virus type I (HTLV-I) is associated with adult T-cell leukemia, HTLV-I-associated myelopathy/tropical spastic paraparesis and various autoimmune-like disorders. T-cell immune suppression is also associated with HTLV-I infection. Mechanisms of diverse immune dysregulation in HTLV-I infection are obscure. Here, we investigated a potential link between autoimmunity and immune suppression in HTLV-I infection. G14, an IL-2-dependent HTLV-I-negative CD4(+)CD8(+) T-cell line previously established from an HTLV-I-infected rat, constantly proliferated and produced IFN-gamma. IFN-gamma production by G14 cells was dependent on interactions between CD4 and MHC-II, suggesting that G14 cells recognized self-antigens presented by MHC-II on themselves. To examine immune response to G14 cells, we inoculated G14 cells into syngeneic naive rats. Interestingly, T-cells isolated from these rats vigorously proliferated when stimulated with G14-Tax cells that stably expressed HTLV-I Tax, but not with G14 cells. G14-Tax-mediated T-cell proliferation was abrogated by antibodies to CD80 and CD86 that were up-regulated in G14-Tax cells. T-cells propagated by repetitive G14-Tax cell stimulations in culture with IL-2 expressed CD4, CD25 and cytolytic T lymphocyte-associated antigen 4 (CTLA-4), produced abundant amounts of IL-10 and IFN-gamma in response to G14 cells and suppressed growth of G14 cells mainly through supernatant-mediated mechanisms. Similar IL-10- and IFN-gamma-producing CD4(+)CD25(+)CTLA-4(+) T-cells were predominantly induced in culture of splenocytes from HTLV-I-infected rats following stimulation with G14-Tax cells. These results implied that expression of Tax in the otherwise low immunogenic autoreactive T-cells induced IL-10- and IFN-gamma-producing T-cell responses with regulatory effects against the autoreactive cells. Our findings provide new insights into the complex immune conditions underlying HTLV-I-associated diseases.

Beyersdorf N, Gaupp S, Balbach K, Schmidt J, Toyka KV, Lin CH, Hanke T, Hünig T, Kerkau T, Gold R (2005). "Selective targeting of regulatory T cells with CD28 superagonists allows effective therapy of experimental autoimmune encephalomyelitis" J Exp Med 202(3):445-55. PubMed

CD4+CD25+ regulatory T cells (T reg cells) play a key role in controlling autoimmunity and inflammation. Therefore, therapeutic agents that are capable of elevating numbers or increasing effector functions of this T cell subset are highly desirable. In a previous report we showed that a superagonistic monoclonal antibody specific for rat CD28 (JJ316) expands and activates T reg cells in vivo and upon short-term in vitro culture. Here we demonstrate that application of very low dosages of the CD28 superagonist into normal Lewis rats is sufficient to induce T reg cell expansion in vivo without the generalized lymphocytosis observed with high dosages of JJ316. Single i.v. administration of a low dose of the CD28 superagonist into Dark Agouti (DA) rats or Lewis rats that suffered from experimental autoimmune encephalomyelitis (EAE) proved to be highly and equally efficacious as high-dose treatment. Finally, we show that T reg cells that were isolated from CD28-treated animals displayed enhanced suppressive activity toward myelin basic protein-specific T cells in vitro, and, upon adoptive transfer, protected recipients from EAE. Our data indicate that this class of CD28-specific monoclonal antibodies targets CD4+CD25+ T reg cells and provides a novel means for the effective treatment of multiple sclerosis and other autoimmune diseases.

Lin CH, Hünig T (2003). "Efficient expansion of regulatory T cells in vitro and in vivo with a CD28 superagonist" Eur J Immunol 33(3):626-38. PubMed

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.

Elflein K, Rodriguez-Palmero M, Kerkau T, Hünig T (2003). "Rapid recovery from T lymphopenia by CD28 superagonist therapy" Blood 102(5):1764-70. PubMed

Slow recovery of T-cell numbers and function contributes to the high incidence of life-threatening infections after cytotoxic cancer therapies. We have tested the therapeutic potential of a novel class of superagonistic CD28-specific antibodies that induce polyclonal T-cell proliferation without T-cell receptor engagement in an experimental rat model of T lymphopenia. We show that in lethally irradiated, bone marrow-reconstituted hosts, CD28 superagonist is able to dramatically accelerate repopulation by a small inoculum of mature, allotype-marked T cells. CD28-driven recovery of CD4 cells was superior to that of CD8 T cells. CD28 superagonist- expanded CD4 T cells had maintained repertoire diversity and were functional both in vitro and in vivo, suggesting that treatment with a human CD28-specific superagonist will protect T-lymphopenic patients from opportunistic infections.