Inhibition of mitogen-induced human lymphocyte proliferative responses by tetracycline analogues.

The effect of tetracyclines on mitogen-induced proliferative responses of human lymphocytes was examined. The results showed that of the three tetracycline analogues studied, doxycycline possessed the most potent inhibiting effects. This occurred at drug concentrations (1--10 micrograms/ml) easily attainable in serum during conventional dosage schedules. Other investigations have shown that tetracyclines also interfere with neutrophil function. Taken together, these findings may have clinical significance. Recovery from serious infections generally requires some minimal host immune responses, and the immunosuppressive side-effects of tetracyclines may have detrimental effects on patients with debilitating illnesses or impaired immunological defence mechanisms. Furthermore, tetracyclines may share some common properties of conventional immunosuppressive drugs, such as cytotoxicity, teratogenicity and cancerogenicity. The long-term use of tetracyclines for conditions such as chronic bronchitis, bronchiectasis and acne vulgaris needs to be re-examined.