Immunological aspects of new quinolones.

The effects of new quinolones on the immune system have been mainly studied in vitro. Despite some conflicting results due to variations in study methodologies, certain conclusions can be drawn. Clinically relevant concentrations of most quinolones seem to have no direct effect on isolated immune parameters such as phagocytic cell functions, lymphocyte proliferation, immunoglobulin production, gamma-interferon secretion and bone-marrow progenitor cell proliferation. In contrast, the production of certain cytokines (IL-1, IL-2) and colony stimulating factors by stimulated lymphocytes and splenocytes is enhanced in the presence of clinically achievable concentrations of the drugs. IL-2 production is also enhanced when higher concentrations of quinolones are added to stimulated lymphocytes. However, most other functions such as IL-1 and TNF production, and proliferation of lymphocytes and bone marrow progenitor cells are inhibited in vitro by concentrations of quinolones exceeding 50 micrograms/ml. In vivo studies on immunomodulatory effects of new quinolones are few and are generally in agreement with the in vitro findings. Only very high dosages administered to experimental animals cause suppressive effects, while therapeutic doses are usually not associated with measurable alterations in immune functions. Recent reports on stimulatory effects of therapeutic doses of ciprofloxacin on bone marrow myeloid progenitor cells in irradiated, neutropenic mice, warrant further investigations in experimental animals as well as in neutropenic and bone marrow transplant patients treated with the new quinolones.