CD4 and Arthritis: Concomitant depletion of IL-17 and CD4+CD25+ T lymphocytes from these Borrelia-vaccinated and -infected mice resulted in massive edema of the hind paws, extensive erosion of cartilage, bone, and synovial tissue of the tibiotarsal joints, and pannus formation into the joint space, indicating that these cells played a significant role in the protection from Borrelia-induced arthritis mediated by neutralization of IL-17 [53].