Lymphocyte transformation test (LTT)

Peripheral blood mononuclear cells (PBMCs) were isolated by density gradient centrifugation from blood that was collected on day 1 before the study drug administration, day 20–22, and day 60. The proliferation of PBMCs (0.15 × 10⁶ cells) in response to amoxicillin (0.25–2 mM), clavulanate (0.0625–0.5 mM), and PHA (5 μg/mL; positive control) was measured using the LTT as previously described.²⁴ The proliferative response was calculated as a stimulation index (SI; cpm in drug‐treated cells/cpm in mock‐treated cells).

PBMCs secreting interferon‐gamma were visualized using ELISpot (MabTech, Nacka Strand, Sweden) by culturing the PBMCs with each drug for 48 h.