Abstract Introduction Clinical differences in individuals with asthma compared to those without may be the result of differences in the immune response. Current biomarkers such as circulating eosinophil counts are inadequate at identifying the presence of asthma or asthma severity. We utilized the 40-color fluorescent full-spectrum flow cytometry OMIP-069 panel for in-depth immunophenotyping of asthma. Methods Patients were recruited from the Asthma Center at Cleveland Clinic. Blood samples underwent Ficoll separation, cryopreservation, and were then batch-labeled for flow cytometry according to OMIP-069. Clinical data from asthma patients were collected from their medical records. Statistical analyses were conducted with R (version 3.5.3) and PRISM. Results We recruited 18 asthmatics (11 severe; 7 non-severe asthma) and 7 healthy individuals. People with asthma and those without asthma had similar age mean (standard deviation): asthma 51.6 (15.85); healthy control 49.86 (7.43), p 0.05. Severe asthmatics had lower baseline % predicted pre-bronchodilator forced expiratory volume in one second (FEV1) asthma 66% (17%) vs. healthy 92% (8%), p = 0.001. Healthy individuals had higher mature natural killer (NK) cells compared to asthmatics healthy controls 10.57% (5.14%); asthma 6.20% (4.02%) in asthma, p = 0.034. In people with asthma, increasing FEV1% is associated with increasing % of innate lymphoid cells (ILCs; R = 0.55, p = 0.0182), % of naïve T cells (CD4+CD45RA+CCR7+) (R = 0.53, p = 0.024), and % of naïve CD4 cells (R = 0.53, p = 0.023). % of non-classical monocytes decreased with increasing post-bronchodilator FEV1% (R = -0.55, p = 0.019) in asthma. The % of natural killer T cells (NKT: CD3+ TCRγδ-CD56+CD2+CD8-) increased with %FEV1 reversibility (R = 0.63, p = 0.0045). Discussion People with severe asthma, defined by low FEV1%, have fewer circulating ILCs, naïve CD4 cells, and naïve T cells. Fewer ILCs in asthma reflect increased lung homing of these cells, where they drive inflammation. Similarly, there are fewer naïve CD4 cells in the blood as they migrate to the lung in asthma. The low % of naïve T cells reflect chronic inflammation. While NKT cells are involved in asthma, the exact mechanism is unknown. The novel subset (CD3+TCRγδ-CD56+CD2+CD8-) is associated with %FEV1 reversibility. Conclusion Circulating immune subsets predict lung function. These subsets could serve as biomarkers for predicting inflammation and airway constriction. This abstract is funded by: RPC - Cleveland Clinic Internal Funding
Solanki et al. (Fri,) studied this question.