To evaluate the ability of S1PR1-specific tracer for the assessment of other inflammatory diseases, as well as to further understand the role of S1PR1 in response to pathogen infection, we performed ex vivo biodistribution, microPET, and immunohistochemistry staining studies to investigate S1PR1 expression on S. aureus-infected mice using our recently reported S1PR1-specific radiotracer [ [18]F]TZ4877 [33–35]. Here, S1PR1 is linked to infection.