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Background: Immunosuppressive therapy with mammalian target of rapamycin inhibitors (mTORi) requires maintenance of an effective inhibition of the alloimmune response, whereas reducing drug-related nephrotoxicity. Therapeutic monitoring is based on mTORi trough levels, which do not necessarily reflect biologic effects on the PI3K-Akt-mTOR pathway and hence may often result in under-immunosuppression or over-immunosuppression., Methods: Phosphorylation of p70S6 kinase was studied by phosphoflow cytometry and by Western blot in both peripheral blood monocyte cells and CD3+ T cells of renal transplant recipients (RTX) receiving tacrolimus (n=34) or cyclosporine A (CsA) (n=24) or an mTORi (n=26). 16 healthy age-matched volunteers served as a control group. To clarify whether p70S6K activity is varying among CD4(+) T-cell subsets, cell sorted CD4(+)CD25(hi) regulatory T cells (Tregs) and CD4(+)CD25- T cells were analyzed for p70S6K phosphorylation., Results: Simultaneous analysis of p70S6K phosphorylation by phosphoflow cytometry and Western blot showed high correlation in peripheral blood mononuclear cells of renal transplant patients (r=0.91, P<0.001). Mammalian target of rapamycin inhibition was associated with marked reduction of p70S6K phosphorylation compared to healthy volunteers or RTX patients receiving calcineurin inhibitors (all P<0.001) but did not correlate with mTORi trough levels. Interleukin-2 production in mitogen-stimulated CD3(+) T cells correlated with the degree of p70S6K phosphorylation in everolimus-treated patients. p70S6K phosphorylation in CD4+CD25(hi) Tregs was significantly lower compared to CD4(+)CD25- T cells (n=3). In mTORi treated RTX recipients, p70S6K phosphorylation was selectively reduced in CD4(+)CD25- T cells leaving CD4(+)CD25(hi) Tregs unimpaired., Conclusion: Phosphoflow cytometric quantification of p70S6K phosphorylation may play an adjunct role to pharmacodynamically guide an individualized mTORi therapy. It may have potential to be used in purity testing of Treg suspensions generated for adoptive tolerogenic therapies.

The peripheral chemokine receptors chemokine receptor 3 (CXCR3) and CC chemokine receptor 5 (CCR5) have been reported to be associated with allograft rejection. The impact of the expression of immunosuppressive drugs on peripherally circulating CD4(+) T cell subsets after renal transplantation is unknown. Expression of CXCR3 and CCR5 was investigated by flow cytometry in 20 renal allograft recipients participating in a prospective, randomized trial (NCT00514514). Initial immunosuppression consisted of basiliximab, cyclosporin A (CsA), mycophenolate sodium and corticosteroids. After 3 months, patients were treated either with CsA, mycophenolate sodium (MPA) plus corticosteroids (n = 6), CsA and everolimus plus corticosteroids (n =8) or CsA-free (CsA(free)) receiving everolimus, MPA and corticosteroids (n = 6). After initial reduction of CD4(+) forkhead box protein 3 (FoxP3)(+) and CD4(+) CD25(hi) FoxP3(+) regulatory T cells (T(regs)) (P < 0.05; P < 0.01), 3-month post-transplant percentages of T(regs) were reconstituted in CsA(free) and CsA(lo) arms compared to CsA(reg) 12 months post transplant. Expression of CCR5 and CXCR3 on CD4(+) FoxP3(+) and CD4(+) FoxP3(-) T cells 12 months post transplant was increased in CsA(free) versus CsA(reg). Increase in CCR5(+) CXCR3(+) co-expressing CD4(+) FoxP3(-) cells between 3 and 12 months correlated negatively with the glomerular filtration rate (GFR) slope/year [modification of diet in renal disease (MDRD); r = -0.59, P < 0.01]. CsA, but not everolimus, inhibits both T(reg) development and expression of CXCR3 and CCR5 on CD4(+) T cell subsets. Increase in CCR5(+) CXCR3(+) co-expressing CD4(+) FoxP3(-) T cells is associated with early loss in allograft function., (© 2012 The Authors;Clinical and Experimental Immunology © 2012 British Society for Immunology.)

Summary The peripheral chemokine receptors chemokine receptor 3 (CXCR3) and CC chemokine receptor 5 (CCR5) have been reported to be associated with allograft rejection. The impact of the expression of immunosuppressive drugs on peripherally circulating CD4+ T cell subsets after renal transplantion is unknown. Expression of CXCR3 and CCR5 was investigated by flow cytometry in 20 renal allograft recipients participating in a prospective, randomized trial (NCT00514514). Initial immunosuppression consisted of basiliximab, cyclosporin A (CsA), mycophenolate sodium and corticosteroids. After 3 months, patients were treated either with CsA, mycophenolate sodium (MPA) plus corticosteroids ( n = 6), CsA and everolimus plus corticosteroids ( n = 8) or CsA-free (CsAfree) receiving everolimus, MPA and corticosteroids ( n = 6). After initial reduction of CD4+forkhead box protein 3 (FoxP3)+ and CD4+CD25hiFoxP3+ regulatory T cells (Tregs) ( P < 0·05; P < 0·01), 3-month post-transplant percentages of Tregs were reconstituted in CsAfree and CsAlo arms compared to CsAreg 12 months post transplant. Expression of CCR5 and CXCR3 on CD4+FoxP3+ and CD4+FoxP3- T cells 12 months post transplant was increased in CsAfree versus CsAreg. Increase in CCR5+CXCR3+ co-expressing CD4+FoxP3- cells between 3 and 12 months correlated negatively with the glomerular filtration rate (GFR) slope/year [modification of diet in renal disease (MDRD); r = −0·59, P < 0·01]. CsA, but not everolimus, inhibits both Treg development and expression of CXCR3 and CCR5 on CD4+ T cell subsets. Increase in CCR5+CXCR3+ co-expressing CD4+FoxP3- T cells is associated with early loss in allograft function. [ABSTRACT FROM AUTHOR]