It has been shown that human gamma delta T cells expressing the V delta 1 T cell receptor (TCR) respond to the spirochete Borrelia burgdorferi. Lysates of 3 Borrelia genospecies triggered the proliferation of peripheral-blood mononuclear cells not only from patients with skin manifestations of Borrelia infection and from patients with Lyme arthritis but also from healthy donors. However, with the exception of 1 patient with Lyme arthritis, no selective expansion of V delta 1-expressing gamma delta T cells was induced. In contrast, synovial-fluid mononuclear cells (SFMC) from 3 of 5 patients with Lyme arthritis responded with a selective outgrowth of V delta 1 gamma delta T cells. V delta 1 gamma delta T cell lines established from SFMC coexpressed various TCR V gamma chains, although V gamma 8 was preferentially used. Thus, the responsiveness to Borrelia antigens is not a general property of V delta 1-expressing gamma delta T cells but is largely restricted to V delta 1 gamma delta T cells recruited into the inflamed tissue.