Immunosuppressive activity of tilmicosin on the immune responses in mice

Tilmicosin, a semi-synthetic macrolide antibiotic that is only used in the veterinary clinic, was evaluated for its immunosuppressive activity on the immune responses to ovalbumin (OVA) in mice. Tilmicosin suppressed concanavalin A (Con A)- and lipopolysaccharide (LPS)-stimulated splenocyte proliferation in vitro. BALB/c mice were immunized subcutaneously with OVA on day 1 and 4. Beginning on the day of boosting immunization, the mice were administered intraperitoneally with tilmicosin at a single dose of 10, 30, and 90 mg/kg for 10 consecutive days. On day 14, blood samples were collected for measuring specific total-immunoglobulin G (total-IgG), IgG1, IgG2b, and splenocytes were harvested for determining lymphocyte proliferation and interleukin-2 (IL-2), interferon-γ (IFN-γ), IL-4 production. The results demonstrated that tilmicosin could significantly suppress Con A-induced splenocyte proliferation in a dose-dependent manner, decrease LPS-and OVA-induced splenocyte proliferation only at high concentration, produced less IL-2, IL-4, and IFN-γ as compared to the control in the OVA-immunized mice. Moreover, the OVA-specific IgG, IgG1, and IgG2b levels in the OVA-immunized mice were reduced by tilmicosin. These results suggest that tilmicosin could suppress the cellular and humoral immune response in mice.