Is ‘timing’ important for cytokine polarization?

A comparison of the longitudinal cytokine responses of cattle to infection with intracellular Mycobacterium bovis and extracellular Onchocerca ochengi illustrates the development of reciprocal interferon-γ and interleukin-4 responses, which result ultimately in an infection-induced type-1 or type-2 polarization, respectively. These kinetic studies of natural host–pathogen relationships show that the cytokine responses to infection fluctuate over time, resulting in periods of polarization and nonpolarization before the establishment of a chronic infection. Here, we discuss our data from cattle in the light of the current understanding of cytokine polarization towards infection in mouse models and humans.