Effects of Regulatory T Cell Depletion in BALB/c Mice Infected with Low Doses of Borrelia burgdorferi

We previously demonstrated that a depletion of regulatory T (Treg) cells in Lyme arthritis-resistant C57BL/6 mice leads to pathological changes in the tibiotarsal joints following infection with Borrelia burgdorferi. Here, we assessed the effects of Treg cells on the response to B. burgdorferi infection in BALB/c mice, which exhibit infection-dose-dependent disease and a different sequence of immune events than C57BL/6 mice. The depletion of Treg cells prior to infection with 1 x 10(2), but not 5 x 10(3), organisms led to increased swelling of the tibiotarsal joints. However, Treg cell depletion did not significantly affect the development of histopathology at these low doses of infection. BALB/c mice depleted of Treg cells before infection with 1 x 10(3) spirochetes harbored a higher borrelial load in the hearts and exhibited higher levels of serum interleukin-10 five weeks later. These results indicate that Treg cells regulate certain aspects of the response to B. burgdorferi in a mouse strain that may display a range of disease severities. As the presentation of Lyme disease may vary among humans, it is necessary to consider multiple animal models to obtain a complete picture of the various means by which Treg cells affect the host response to B. burgdorferi.

Automated summary

We investigated the effects of Treg cells on B. burgdorferi infection in BALB/c mice, which have a different immune response compared to C57BL/6 mice. Depletion of Treg cells before infection caused increased joint swelling at low infection doses, but did not significantly affect histopathology. Mice with higher borrelial load in their hearts and higher levels of serum interleukin-10 were observed when Treg cells were depleted before infection with a higher dose. Multiple animal models are necessary to understand the role of Treg cells in the host response to B. burgdorferi due to the variability in Lyme disease presentation in humans.