Differential Type 2 cytokine responses and group 2 innate lymphoid cell (ILC2) activation among 44 strains of mice in the Collaborative Cross following Alternaria extract challenge

Allergic diseases are caused by genetic and environmental factors. We evaluated the allergic phenotype mediated by group 2 innate lymphoid cell (ILC2) using Collaborative Cross (CC) mouse strains. CC strains and founder strains were challenged intratracheally with Alternaria extract (Alt-ext) using two protocols. In the first protocol, lungs were harvested 6 hours after a single Alt-ext challenge for cytokine detection by ELISA in 44 CC strains and 6 founder strains. In the second protocol, lung ILC2 were detected by flow cytometry in 42 CC strains and 6 founder strains 24 hours after 4 consecutive days of Alt-ext challenge. In the first protocol, amongst the CC strains, there were statistically significant differences in lung IL-5, IL-13, and TSLP protein expression and there were correlations between IL-5 and IL-13 (r2=0.7215, p<0.0001), but no correlation between TSLP and IL-5 (r2=0.0063, p=0.58) or between TSLP and IL-13 (r2=0.0002, p=0.92). In the second protocol, there was a correlation between lung ILC2 number after 4 consecutive days of Alt-ext challenge and both IL-13 (r2=0.2553, p=0.0004) or IL-33 (r2=0.1069, p=0.03), but there was no correlation between the lung ILC2 number and IL-5 (r2=0.0585, p=0.11). We found that there were significant differences in cytokine responses amongst the CC strains that provide the opportunity to define the genetic determinants of the innate allergic immune response. Further, host TSLP production does not seem to be the primary factor in type 2 cytokine responses to Alt-ext challenge.