Borrelia burgdorferi

Borrelia burgdorferi, defined by the NIH, "is a tick-borne obligate parasite whose normal reservoir is a variety of small mammals. Whereas infection of these natural hosts does not lead to disease, infection of humans can result in Lyme disease, as a consequence of the human immunopathological response to B. burgdorferi."

Immune response
It is recognized by toll-like receptors 1 and 2. Mutations in TLR1 are associated with heightened Th1 inflammatory responses and antibiotic-refractory Lyme arthritis