The general immunopharmacology of levamisole

The need for treatments to correct an immunological defect, or to restore an impaired immune response asociated with disease or ageing, has led to the development of nonspecific immunoactive agents. Levamisole, a synthetic low molecular weight compound, is the first member of a new class of drugs which can increase the functions of cellular immunity in normal, healthy laboratory animals. The properties of levamisole have contributed to improved understanding of the molecular events which mediate or trigger immune responses. Levamisole can act either as an immunostimulant agent or an immunosuppressive agent. These apparently paradoxical effects depend upon the dose administered, the timing of its administration, the experimental assay used to measure effects, and the host genetic background. Levamisole's potential for opposite effects explains certain apparent inconsistencies observed in experimental or clinical assays. The drug's actions are modulated by the interaction between the T-cell recruiting efficacy of the sulphur moiety and the cholinergic effects of the imidazole ring. The clinical implications resulting from the immunopharmacological properties of levamisole are obvious: one should avoid its use in diseases without known association with an immune defect, and always attempt to correlate clinical data with modifications of immune parameters, since the therapeutic usefulness of correctly administered levamisole parallels improvement in tests of cellular immunity. Immunomodulators act by modifying the functions of the host cells involved in defences against invaders, and the effectiveness of an immunotherapeutic drug is dependent upon characteristics of the individual host. Thus, therapy with such drugs must be individualised; the appropriate agent and dosage should be chosen according to the immune capabilities of individual patients.