IL1RL1 and asthma: The allele associated with severe asthma at Signal C (rs17027258 [A]) was associated with elevated IL1RL1 mRNA levels of the transcripts encoding transmembrane IL1RL1 but not with those encoding the soluble isoform in HBECs (P < 0.05) (Figure 3, C and D), in agreement with the direction of effect observed in lung tissue.