Suppression of co-stimulatory molecule expressions on splenic B lymphocytes by a macrolide antibiotic, roxithromycin in vitro.

The influence of a macrolide antibiotic, roxithromycin (RXM), on co-stimulatory molecule expression was examined using in vitro cell culture technique. Spleen cells obtained from BALB/c mice 10 days after immunization with 8.0 micrograms of haemocyanin absorbed to 4.0 mg aluminum hydroxide were cultured in the presence of 100.0 micrograms/ml haemocyanin and various concentrations of RXM for 72 h. Low concentrations (1.0 and 2.5 micrograms/ml) of RXM did not influence cell activation induced by antigenic stimulation, whereas RXM showed a suppressive effect on blastic activity of the cells when the agent was added to the cultures at more than 5.0 micrograms/ml. RXM did not affect blastic activity of splenic T cells by anti-CD3 monoclonal antibody stimulation even when the cells were cultured in the presence of 10.0 micrograms/ml RXM. Addition of anti-CD80 and anti-CD86 monoclonal antibody to cell cultures caused significant suppression of cell activation by antigenic stimulation. We next examined the influence of RXM on co-stimulatory molecule expressions on splenic B cells in response to antigenic stimulation. Addition of RXM at a concentration of 5.0 micrograms/ml into cell cultures remarkably suppressed co-stimulatory molecule, CD40, CD80 and CD86, expressions, which enhanced by antigenic stimulation in vitro.