CD19(+) cells produce IFN-gamma in mice infected with Borrelia burgdorferi.

We have recently shown that production of IFN-gamma and IL-10, but not IL-4 is specifically induced in the lymph nodes of C3H/HeJ (disease susceptible) and C57BL/6J (disease resistant) mice 1 week after infection with Borrelia burgdorferi spirochetes. The present study was conducted to determine the phenotypes of ex vivo lymph node cells obtained from infected mice of both strains at this time point. The percentages of CD3(+), CD4(+), CD8(+), TCRalpha/beta (+) and TCRgamma/delta (+) cells decreased in both strains of mice compared to LN from naive mice. In contrast, there was a threefold increase in the proportion of CD19(+) cells. In view of this expansion of the B cell proportion, we examined the ability of purified CD19(+) cells and CD43(+) cells to produce both IL-10 and IFN-gamma when the cells were restimulated in vitro with B. burgdorferi freeze-thawed spirochetes. As expected, CD43(+) cells were able to produce both cytokines, but not IL-4. Surprisingly, CD19(+) (B) cells also were able to produce IFN-gamma in comparable amounts, in addition to IL-10. Intracellular staining of CD19(+) cells with anti-IFN-gamma antibody confirmed this finding. We discuss this novel phenomenon in terms of its possible underlying mechanisms and its relevance, both in the context of the immunology of Lyme disease and that of other infectious diseases.