The administration of interleukin-12 (IL-12) antibodies to Borrelia burgdorferi-infected C3H/HeN-scid mice increased the severity of acute
Lyme arthritis. These results contrasted with the reduction of
Lyme arthritis by IL-12 antibodies in immunocompetent animals. These data suggest that downregulation of innate immunity in SCID mice in the absence of B- and T-cell responses leads to an exacerbation of joint inflammation.