Cross-Linking of CD45 on Suppressive/Regulatory T Cells Leads to the Abrogation of Their Suppressive Activity In Vitro

Abstract

CD4+CD25+ T cells have immunoregulatory and suppressive functions and are responsible for suppressing self-reactive cells and maintaining self-tolerance. In addition to CD4+CD25+ T cells, there is some evidence that a fraction of CD4+CD25− T cells exhibit suppressive activity in vitro or in vivo. We have shown, using aged mice, that aging not only leads to a decline in the ability to mount CD4+CD25− T cell responses, but, at the same time, renders aged CD4+CD25− T cells suppressive. In this study we report two newly established mAbs that could abrogate the suppressive function of aged CD4+CD25− T cells. These mAbs recognized the same protein, the transmembrane phosphatase CD45. Cross-linking of CD45 on aged CD4+CD25− T cells was required for the disruption of their suppressive activity. Surprisingly, these mAbs also abrogated the suppressive action of CD4+CD25+ T cells in vitro. Our results demonstrate an unexpected function of CD45 as a negative regulator neutralizing the suppressive activity of aged CD4+CD25− and young CD4+CD25+ T cells.

Defective Activation of Protein Kinase C and Ras-ERK Pathways Limits IL-2 Production and Proliferation by CD4+CD25+ Regulatory T Cells

“…Additionally, Zhang et al (41) have shown that raft-excluded CD45 results in sustained ERK activation, enhanced synaptic raft clustering, and increased IL-2 production by T cells following activation. That the positioned exclusion of CD45 or other phosphatases away from the immunological synapse during T cell activation may be altered in Tregs is an intriguing possibility which should be closely examined in light of a recent report demonstrating that the cross-linking of CD45 on Tregs with specific mAbs could abrogate their suppressive action (42).…”

In vivo expansion of CD4+Foxp3+ regulatory T cells mediated by GITR molecules

“…S2). In contrast, the other reagents examined, IL-4 [13], DTA1 [10], 59.32 mAb [11], and conditioned medium from DCs treated with LPS [designated LPS-CM [14]], all of which have the ability to abrogate the suppression by Treg cells, had no co-stimulatory effect on the cell-proliferation. The G3c mAb itself had no effect in the absence of anti-CD3 Ab (less than 500 cpm in all experiments).…”

“…Anti-GITR mAb, DTA1 [rat IgG2b [10]], and anti-CD45 mAb, 59.32 [rat IgM [11]], was made from ascites in SCID mice and purified by 50% ammonium sulfate precipitation. The supernatant (SN) from P815 cells transduced with murine IL-4 [12] was used as a source of IL-4.…”

Antigen-independent generation of a unique CD4 T cell-subset with aging and its persistent unresponsiveness

“…We have reported that a novel anti-CD45 Ab (59.32) could break the suppressive activity of Treg cells, and, at the same time, act on non-Treg cells as a strong co-stimulatory Ab [8]. The co-stimulatory effect on non-Treg cells was unique (Fig.…”

“…Mittler. Hybridomas secreting anti-GITR (G3c, rat IgM) or anti-CD45 (59.32, rat IgM) [8] Ab were established in our laboratory. Paraquat dichloride was purchased from Dr. Ehrenstorfbr GmbH (Augsburg, Germany).…”