Aberrant Th1 responses at the expense of Th2 immunity in Pik3cd ^E1020K/+ lungs following HDM sensitization. (A) Scatter plot comparing gene expression in CD4 T cells from WT and Pik3cd^E1020K/+ HDM-treated mice (cluster 1 from Fig. 1 G). DEGs upregulated in WT CD4 T cells in red, and genes upregulated in Pik3cd^E1020K/+ CD4 T cells in blue. (B) CD4⁺ T cells from scRNAseq of total CD45⁺ lung immune cells (cluster 1 from Fig. 1 G) were re-clustered to identify five unique clusters (0–4) of CD4⁺ T cells. Left: UMAP showing distribution of clusters 0–4; identities of each cluster were assigned based on cluster-specific gene expression. Right: Proportion of cells from each cluster in indicated mice. (C) Seurat heatmap showing expression of cluster-defining genes for indicated populations. (A–C) Cells from three mice were analyzed per genotype and condition. (D) Representative flow cytometry plots of intracellular IFNγ and IL-5 expression in lung CD4⁺ T cells (liveCD45⁺TCRβ⁺CD4⁺CD8⁻) from indicated mice. (E–H) Frequencies of lung CD4⁺ T cells expressing (E) IL-5; (F) IL-4; (G) IFNγ; and (H) IL-2 from indicated groups. (D–H)n = 9–10 for each group, pooled from two independent experiments. (I–L) TCRα-deficient recipient mice were injected with 1 × 10⁶ WT or Pik3cd^E1020K/+ naïve CD4 T cells 14 days prior to HDM sensitization. HDM was administered intranasally as indicated. n = 9–10 for each group, pooled from two independent experiments. (I) Experimental design. (J) Cell counts of lung CD4 T cells (liveCD45⁺TCRβ⁺CD4⁺CD8⁻) from the indicated groups. (K) Frequencies of IFNγ⁺ (left) and IL-4/5/13⁺ (right) lung CD4 T cells from the indicated groups. Frequencies of IL-4/5/13⁺ cells were calculated using Boolean (or) gating. (L) Cell counts of eosinophils (liveCD45⁺CD3⁻NK1.1⁻CD19⁻CD11b⁺Ly6G⁻SiglecF⁺) from lungs of the indicated mice. Statistical comparisons were made using unpaired t tests. *P < 0.05, **P < 0.01, ***P < 0.001.