Johnston is a licensed veterinarian and board certified veterinary surgeon who has been working in the biomedical research field since 2009 as well as being co-owner of equine specialty clinic in mid-Michigan. Johnston's experience includes models of sepsis, acute lung injury/ARDS, ischemia reperfusion injury, acute and chronic kidney failure, diabetes (type 1 and type 2) and intracerebral hemorrhage; all of which exhibit some component of immune system dysregulation.