(Left) Selected IgM immunoblot reactivities. Lane 1, serum band locator control showing several bands, including the significant 41-kDa protein, 39-kDa protein, and OspC (arrows). Lane 2, serum sample from a patient with early LB with EM. Lane 3, serum sample from a patient with early disseminated LB with multiple EM lesions. Note the larger number of bands observed in serum of the patient with early disseminated LB. (Right) Selected IgG immunoblot reactivities. Lane 1, serum band locator control showing several immunoreactive bands, including those considered significant in the IgG blot criteria (arrows). Lane 2, serum sample from a patient with early disseminated LB with neurological involvement. Lane 3, serum sample from a patient with Lyme arthritis. Lane 4, serum sample from an individual who received three doses of OspA vaccine. In lane 4, note the strong reactivity with OspA (31 kDa) and other antigens below OspC.