Ketotifen treatment of adverse reactions to foods: clinical and immunological effects

The effect of aging on host defences. Implications for therapy

Immunosenescence is a well known physiological phenomenon resulting from reduced efficiency of the immune system in the elderly. It has been studied both in animal models and in humans. In this review attention is focused on T cell responsiveness, since this cell type is both a marker of the immune response and one of the main targets of several drugs. For this latter reason, most studies of the effect of drugs on the immune system have been performed with reference to the effects on T lymphocytes. In the second part of the article experimental data concerning several drugs and drug classes [steroids, calcium antagonists, theophylline, histamine H1- and H2-receptor antagonists, sodium cromoglycate (cromolyn sodium), pirenzepine, rosaprostol, beta 2-mimetics, antibiotics and antibacterials] and immune responsiveness are reviewed. Lastly, the clinical perspectives of pharmacological treatment in aged subjects in relation to immunosenescence are evaluated.

Antiallergic drugs and the immune response. Interactions and possible clinical relevance

Since the pharmacological treatment of allergic diseases is used in patients with alteration of the immune response due to atopy and possible concomitant infections, we have investigated the possible effects of such drugs as cromolyn, theophylline, ketotifen, oxatomide, astemizole, fenoterol, pirenzepine, and rosaprostol on the in vitro immune response, in order to obtain experimental data and, as a consequence, clinical conclusions. In a series of investigations by our group and other authors the following immunological parameters have been considered: T cell activation induced by different pathways (i.e. autologous stimulation, PHA, anti-CD3, -CD2 and -CD28 monoclonal antibodies), and lymphokine production (i.e. IL-1, IL-2 and gamma-IFN). For a more detailed experimental model the experiments have been performed both in bulk culture and by using T cell clones derived from the peripheral blood. The results show cromolyn to have an enhancing effect, theophylline and ketotifen a suppressing effect, whereas the remainder show no effect on the immune response. These data are considered and discussed from the aspect of their possible clinical relevance and also in light of the in vivo data previously reported.

Theophylline and the immune response: in vitro and in vivo effects

We analyzed the in vitro and in vivo effects of theophylline on various immunological parameters including proliferation of peripheral mononuclear cells (PMNC) in response to phytohemagglutinin (PHA), anti-T3 and anti-T11 monoclonal antibodies (MAb), PHA-induced interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) production by PMNC, interleukin-1 (IL-1) production by accessory cells, PHA-induced IL-2 production by T-cell clones, and PHA- and anti-T3 MAb-induced DNA synthesis by T cell clones. Results showed that theophylline inhibited PHA- and anti-T3-induced proliferation of both PMNC and T-cell clones, whereas the PMNC proliferation induced by MAb anti-T11 was not affected. The inhibition appeared to be dose-dependent and strictly related to the presence of the drug in the culture. Moreover, PHA-induced IL-2 production by both PMNC and T-cell clones also appeared to be reduced by theophylline. IL-1 production by accessory cells was not affected. These data suggest that the immunological inhibition exerted by theophylline is confined to the T-cell compartment, mainly by acting on structure(s) related to the T3/Ti complex, the primary site for T-cell activation. The alternative pathway of T-cell activation (i.e., via T11 site) seems unaffected. In addition, these results suggest possible clinical relations between the inhibition of the immune response and the plasma levels of the drug reached after a "once daily" or "twice daily" oral ingestion of slow-release theophylline products.

Inhibiton of the colony-forming capacity of human T-lymphocytes exerted by theophylline

The effects of theophylline on T-lymphocyte colony formation were investigated both by in vitro studies (adding theophylline in cultures at three different concentrations--5, 15 and 30 micrograms/ml) and by in vivo experiments (after oral ingestion of 10 mg/kg time-released theophylline) in a group of young healthy volunteers. In vitro the drug showed a significant dose-dependent inhibitory effect on both peripheral mononuclear cells (PMNC) and purified T-lymphocyte colony formation. No significant differences in PMNC colony formation before and 12 h after the oral ingestion of theophylline was detected in the in vivo study, even if at the same time the plasma concentration of the drug remained at therapeutic level in every subject. In addition, in vitro experiments mimicking the in vivo conditions suggested that the apparent disagreement between the in vitro and in vivo results was due to experimental procedures (i.e. the inhibitory effect requires the constant presence of the theophylline in the culture medium). The experimental data provided in this study confirm, using different experimental procedures, the results of our recent investigations showing that theophylline exerts an inhibitory effect on T-cell proliferation.

Fenoterol effects on the in vitro immune response

Beta-2-adrenergic agonists are often employed in the treatment of acute bronchostenosis. Following our recent investigations into the influence of some drugs (cromolyn, ketotifen, theophylline) on the immune response, in this study we analyzed the in vitro effects of fenoterol (beta-2-adrenergic agonist) on the immune response. The mitogen-(PHA)-induced proliferation of peripheral mononuclear cells (PMNC), the PMNC proliferation induced by anti-T3 and anti-T11 monoclonal antibodies (MAbs), the PHA-induced lymphokine--interleukin 2 (IL-2) and interferon-gamma (IFN-gamma)--production were studied in ten healthy volunteers. Since the plasmatic peak of fenoterol following a single inhalation of 200 micrograms is about 20 ng/ml, in the experiments herein reported the drug was tested in the cultures at concentrations lower, equal and higher than the plasmatic peak: respectively, 2, 20 and 200 ng/ml. Furthermore, for a more detailed study of T-lymphocyte activities, we also evaluated the effect of fenoterol on T-cell clone proliferation. Our results, which reveal no effects of fenoterol on the studied immunological parameters, acquire relevance when related to our previous reports showing a depression of the immunological response exerted by theophylline and ketotifen.