Effect of long-term and low-dose administration of erythromycin on proliferation of T lymphocytes stimulated with mitogens.

The aim of the study was to assess the effect of long-term low-dose erythromycin (EM) treatment for chronic airway inflammation on proliferation of T cell subsets when stimulated with concanavalin A (Con A) and phytohemagglutinin (PHA). CD8+ cells are much more responsive to Con A compared to PHA. Ten patients with bronchiectasis were administered EM at 400 mg daily for 6 months. The extent of proliferation was assayed by [(3)H] thymidine incorporation and expressed as a stimulation index (SI). The lymphocyte subsets were analyzed including CD3+, CD4+ and CD8+ cells. The SI stimulated with Con A in the last month of therapy was significantly lower compared with that before the start of therapy (p=0.015) and 3 months after the end of therapy (p=0.002). However, EM therapy did not make a significant difference to the SIs when stimulated with PHA. CD3+, CD4+ and CD8+ cells in absolute numbers and CD4+/CD8+ ratios were not different among those harvested at the three time points. Long-term administration of EM may decrease the transformation response of CD8+ cells in patients.