CXCL9 and erythema multiforme: Paradoxically, in response to B. burgdorferi infection, this SNP is associated with excessive immune responses with marked levels of IFN-γ and IFN-γ–inducible chemokines CXCL9 and CXCL10 in serum of patients with EM and even higher levels in joint fluid of those with postantibiotic (postinfectious) Lyme arthritis.