In a mouse model of pneumococcal pneumonia, addition of azithromycin to ceftriaxone induced specific changes in immune-checkpoint ligands (e.g., up-regulation of CD86 and MHC II in neutrophils and CD11b+CD11c+ macrophages) and receptors (e.g., down-regulation of CTLA-4) in bronchoalveolar lavage fluid, which may have contributed to the observed increased survival (31). The gene discussed is CTLA4; the disease is pneumococcal pneumonia.