Representative IgM line immunoblots of patient and control sera. Strains belong to the following species: B31 and PKa2 to B. burgdorferi sensu stricto, PKo to B. afzelii, PBr to B. garinii OspA type 3, PBi to B. garinii OspA type 4, and 20047 to B. garinii unknown OspA type. Sera were obtained from patients with EM, early neuroborreliosis (NB), acrodermatitis chronica atrophicans or Lyme arthritis (late LB), and controls. [p100], not included in the valuation of the IgM blot results (note p100 reactivity of control sera); *, additional antigen on the IgM line blot.