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1 The cyclic AMP phosphodiesterases (PDE) expressed by CD4+ and CD8+ T-lymphocytes purified from the peripheral blood of normal adult subjects were identified and characterized, and their role in modulating proliferation and the biosynthesis of interleukin (IL)-2 and interferon (IFN)-y evaluated. 2 In lysates prepared from both subsets, SK&F 95654 (PDE3 inhibitor) and rolipram (PDE4 inhibitor) suppressed cyclic AMP hydrolysis indicating the presence of PDE3 and PDE4 isoenzymes in these cells. Differential centrifugation and subsequent inhibitor and kinetic studies revealed that the particulate fraction contained, predominantly, a PDE3 isoenzyme. In contrast, the soluble fraction contained a PDE4 (-65% of total activity) and, in addition, a novel enzyme that had the kinetic characteristics of the recently identified PDE7. 3 Reverse transcription-polymerase chain reaction (RT-PCR) studies with primer pairs designed to recognise unique sequences in the human PDE4 and PDE7 genes amplified cDNA fragments that corresponded to the predicted sizes of HSPDE4A, HSPDE4B, HSPDE54D and HSPDE7. No message was detected for HSPDE4C after 35 cycles of amplification. 4 Functionally, rolipram inhibited phytohaemagglutinin-(PHA) and anti-CD3-induced proliferation of CD4+ and CD8+ T-lymphocytes, and the elaboration of IL-2, which was associated with a three to four fold increase in cyclic AMP mass. In all experiments, however, rolipram was approximately 60 fold more potent at suppressing IL-2 synthesis than at inhibiting mitogenesis. In contrast, SK&F 95654 failed to suppress proliferation and cytokine generation, and did not elevate the cyclic AMP content in T-cells. Although inactive alone, SK&F 95654 potentiated the ability of rolipram to suppress PHA-and anti-CD3-induced T-cell proliferation, and PHA-induced IL-2 release. 5 When a combination of phorbol myristate acetate (PMA) and ionomycin were used as a co-mitogen, rolipram did not affect proliferation but, paradoxically, suppressed IL-2 release indicating that cyclic AMP can inhibit mitogenesis by acting at, or proximal to, the level of inositol phospholipid hydrolysis. 6 Collectively, these data suggest that PDE3 and PDE4 isoenzymes regulate the cyclic AMP content, IL-2 biosynthesis and proliferation in human CD4+ and CD8+ T-lymphocytes. However, the ability of rolipram to suppress markedly mitogen-induced IL-2 generation without affecting T-cell proliferation suggests that growth and division of T-lymphocytes may be governed by mediators in addition to IL-2. Finally, T-cells have the potential to express PDE7, although elucidating the functional role of this enzyme must await the development of selective inhibitors. Keywords: CD4+ T-lymphocytes; CD8+ T-lymphocytes; phosphodiesterase inhibitors; proliferation; interleukin-2 generation; phosphodiesterase 3; phosphodiesterase 4; phosphodiesterase 7 IntroductionAlthough glucocorticosteroids are considered the most effective agents currently available for the treatment of asthmatic inflammation, they are not without adverse effe...

The grass pollen allergoid was shown to be safe and clinically efficacious in the management of hay fever with or without asthma (GINA I or II).

No abstract

Inhibition of T-lymphocyte activation may provide a useful approach to the treatment of chronic severe asthma. We compared rapamycin, a novel immunosuppressive drug, with cyclosporine and dexamethasone for its effects in inhibiting proliferation of T lymphocytes from patients with glucocorticoid-resistant and glucocorticoid-sensitive asthma.Phytohemagglutinin-stimulated peripheral blood T lymphocytes from 11 patients with clinically glucocotiicoid-resistant and 8 patients with glucocorticoid-sensitive chronic asthma were tested for sensitivity to these drugs in a highly reproducible proliferation assay. All drugs inhibited proliferation in a dose-dependent manner (10e6 to 10-l' mol/L). T lymphocytes from the patients with glucocorticoid-resistant asthma were significantly less sensitive (p < 0.01) to dexamethasone than those of patients with glucocorticoid-sensitive asthma over a wide concentration range. In contrast, cyclosporine and rapamycin inhibited cells from both patient groups to an equivalent extent. The presence of exogenous interleukin-2 abrogated the inhibitory effect of dexamethasone but not that of cyclosporine or rapamycin, suggesting that dexamethasone may act principally by inhibition of interleukin-2 production, whereas the latter drugs exert distinct or additional inhibitory effects. Stimulation of peripheral blood T lymphocytes with phytohemagglutinin for 24 hours before addition of the drugs abolished the inhibitory effect of dexamethasone and significantly reduced that of cyclosporine. The inhibitory effect of rapamycin was, however, unaltered. These data suggest that dtzcamethasone and cyclosporine exert their effects only at an early stage of T-lymphocyte activation, whereas rapamycin is able to inhibit lymphoblasts. The fact that the inhibitory mechanisms of these drugs are different might explain why cyclosporine and rapamycin are effective in inhibiting T lymphocytes from both patients with glucocorticoid-sensitive and those with glucocotiicoid-resistant asthma. The data further suggest that cyclosporine and rapamycin may be effective for the therapy of glucocotiicoid-resistant asthma. {J ALLERGY CLIN IMMUNOL 1994;93:510-19.)