CD4+T Helper 1 Cells Facilitate Regression of Murine Lyme Carditis

Abstract

Murine Lyme borreliosis, caused by infection with the spirocheteBorrelia burgdorferi, results in acute arthritis and carditis that regress as a result ofB. burgdorferi-specific immune responses.B. burgdorferi-specific antibodies can attenuate arthritis in mice deficient in both B cells and T cells but have no effect on carditis. Because macrophages comprise the principal immune cell in carditis, T-cell responses that augment cell-mediated immunity may be important for carditis regression. To investigate this hypothesis, we examined the course of Lyme carditis in mice selectively deficient in B cells or αβ T cells. Our results show that carditis regresses in B-cell-deficient B10.A^kmice but not in αβ T-cell-deficient mice, independently of the mouse strain background. Despite prominent macrophage infiltrates, hearts fromB. burgdorferi-infected αβ T-cell-deficient mice had less mRNA for tumor necrosis factor alpha as measured by reverse transcription-PCR compared to infected control mice. Anti-inflammatory cytokine mRNA levels were equivalent. Adoptive transfer of gamma interferon-secreting CD4⁺T cells into infected αβ T-cell-deficient mice promoted carditis resolution. These results show that αβ T cells can promote resolution of murine Lyme carditis and are the first demonstration of a beneficial role for CD4⁺T helper 1 cells in this disease.