MCL1 and infection: This response was recently shown to be prevented by macrophage over-expression of the antiapoptotic protein MCL-1 (myeloid cell leukemia 1) which impaired the clearance of S. pneumoniae and Haemophilus influenzae. Importantly, macrophage apoptosis was not shown to occur following infection with S. aureus, indicating important pathogen-specific differences in cellular response to infection [140].