IL1B and Sepsis: We used concentrations of 0.5 ng/ml, 5 ng/ml and 50 ng/ml for 3 reasons: first, extreme sepsis in mammals leads to plasma IL-1β concentrations of 0.5 ng/ml; second, concerns over bioavailability of the proteins led us to test very high concentrations and; third, Shu et al. (2007) used these concentrations in their study of the carotid body.