CD161+ TH2 plays a role in driving eosinophilic inflammation in
AR
In order to identify other atopy and AR-related subsets within lymphoid
and myeloid populations, a flow cytometry panel was specifically
designed for the detection of allergy-related PBMC subsets.
[13] In contrast to whole blood
analysis, PBMC clusters demonstrated non-significant associations with
atopy and AR (Supplementary Figure 2 ). Given that TH2 was
earlier identified as a disease-driving subset by transcriptomic
sequencing, we gated for chemoattractant receptor homologue on TH2
(CRTH2+) positive cells to further enrich for key PBMC subsets with
roles in disease progression of AR. CRTH2 is expressed by a small
fraction (approximately 1.6%) of the PBMC population (Figure
2A ) and is typically expressed on TH2-associated immune cells such as
TH2 and ILC2. [19] In line with
transcriptomic analysis, PTGDR2 (gene encoding CRTH2) was also
differentially expressed between non-AR and AR individuals
(Table 1 ).
UMAP analysis segregated the entire CRTH2+ population into five distinct
clusters representing basophils, TH2, ILC2, TC2 and non-classical
monocytes (Figure 2B ). PhenoGraph clustering subdivided these
five main clusters into 28 distinct subpopulations (K1-K28;Supplementary Figure 3 ). While all CRTH2+ subsets are
reportedly involved in allergy and allergic diseases, cluster ‘K9’ is
highlighted here as the sole subset directly associated with atopy
(Figure 2C ). Cluster ‘K9’ (CD161+ TH2) is a TH2A-like subset
[13] located within the TH2 cluster
(Figure 2D and Supplementary Figure 3 ). Next, we
interrogated CD161+ TH2 for associations with AR. Similar to
eosinophils, frequency of CD161+ TH2 is significantly associated with
both atopy and AR (Supplementary Figure 1B and Figure
2E ). Furthermore, we observed a positive correlation between the
frequencies of CD161+ TH2 and eosinophils (Figure 2F ).
Likewise, frequency of CD161+ TH2 is also positively correlated to
titres of total IgE (Figure 2G ). Taken together, CD161+ TH2
cells may represent a key cellular subset driving atopy and airway
inflammation in AR.