Sustained CD28 Expression Delays Multiple Features of Replicative Senescence in Human CD8 T Lymphocytes

CD28 costimulatory signal transduction in T lymphocytes is essential for optimal telomerase activity, stabilization of cytokine mRNAs, and glucose metabolism. During aging and chronic infection with HIV-1, there are increased proportions of CD8 T lymphocytes that lack CD28 expression and show additional features of replicative senescence. Moreover, the abundance of these cells correlates with decreased vaccine responsiveness, early mortality in the very old, and accelerated HIV disease progression. Here, we show that sustained expression of CD28, via gene transduction, retards the process of replicative senescence, as evidenced by enhanced telomerase activity, increased overall proliferative potential, and reduced secretion of pro-inflammatory cytokines. Nevertheless, the transduced cultures eventually do reach senescence, which is associated with increased CTLA-4 gene expression and a loss of CD28 cell surface expression. These findings further elucidate the central role of CD28 in the replicative senescence program, and may ultimately lead to novel therapies for diseases associated with replicative senescence

Topical treatment of mild to moderate plaque psoriasis with 0.3% tacrolimus gel and 0.5% tacrolimus cream: the effect on SUM score, epidermal proliferation, keratinization, T-cell subsets and HLA-DR expression.

Contains fulltext : 70573.pdf (publisher's version ) (Closed access)BACKGROUND: Tacrolimus gel 0.3% and tacrolimus cream 0.5% were studied and compared with calcipotriol ointment 0.005%, as topical treatment for mild to moderate plaque psoriasis. Tacrolimus is able to inhibit several cellular processes thought to be important in the pathogenesis of psoriasis, e.g. the transcription of proinflammatory cytokines, keratinocyte hyperproliferation and the expression of HLA-DR in lesional psoriatic skin. METHOD: In the present study we investigated the effects of preparations of tacrolimus and calcipotriol ointment on SUM score, hyperproliferation (Ki67-positive keratinocytes), keratinization (percentage keratin 10 (K10)-positive epidermal surface), T-cell subsets (CD4, CD8, CD45RO, CD45RA, CD2, CD25), cells expressing natural killer receptors and HLA-DR expression. The following three topical treatments were studied in chronic plaque psoriasis over a 12-week treatment period: calcipotriol ointment 0.005% twice daily, tacrolimus gel 0.3% twice daily and tacrolimus cream 0.5% twice daily. RESULTS: The mean reductions in SUM score between day 0 and week 12 for calcipotriol ointment, tacrolimus gel and cream were significant. Calcipotriol ointment, and tacrolimus gel and cream had a comparable effect on epidermal proliferation (Ki67-positive cells), but calcipotriol is significantly more effective in normalizing differentiation (K10-positive epidermal surface). Calcipotriol and tacrolimus gel both reduced several lesional T-cell subsets significantly, whereas the effect induced by tacrolimus cream was modest. CONCLUSIONS: Calcipotriol and tacrolimus gel are comparable in reducing the SUM score, the number of Ki67-positive cells and T-cell subsets and HLA-DR expression, although calcipotriol induces a more substantial improvement of keratinization