Since B. abortus resides in all of these cell types, trophoblasts, macrophages, and neutrophils, during infection (27), it is likely that reciprocal interactions between multiple cell types in the placenta drive TNF-α production, which may explain the striking reduction in placental inflammation observed after TNF-α neutralization in B. abortus-infected mice (Fig. 3). Here, TNF is linked to infection.