TAC1 and arthritic joint disease: Therefore, it is interesting to note the paradoxical increase in IL-13 in the bronchoalveolar lavage fluid of OVA-sensitized ASIC1a-/- mice despite decreased levels of substance P. A somewhat similar paradox occurs with ASIC3-/- mice in a murine model of arthritis; ASIC3-/- mice display a lack of pain despite having greater IL-6 levels [83].