IL23A and obesity due to melanocortin 4 receptor deficiency: Obesity and asthma, independently, increase serum IL-23 in human subjects [123, 124], BAL IL-23 is increased to a greater extent in obese as compared to lean mice following exposure to O3 [100], and inhibition of IL-17A, whose expression can be induced by IL-23, reduces increases in airway responsiveness and BAL KC and neutrophils induced by acute exposure to O3 [100, 125].