**1. Introduction**

Asthma was a chronic inflammatory airway disease which characterized by complex pathogenesis, various clinical manifestations and severity. With an increasing prevalence, asthma affecting an estimated 358 million people worldwide [1]. According to the recent epidemiological data in China, there were 45.7 million adult patients with asthma and the total prevalence rate was 4.2% [2]. The cumulative prevalence among children under 14 years of age was 3.02% [3]. The high prevalence and different clinical manifestations lead to various treatment of asthma. Therefore, it was very important to determine the classification and specific markers for the management of asthma.

Francisaca et al. have proposed to classify asthma phenotypes into allergic asthma, eosinophilic asthma, obese asthma, persistent asthma, symptomatic asthma, positive bronchial provocation test with asthma symptoms, positive bronchial provocation test with no asthma symptoms, and negative bronchial provocation test with asthma symptoms [4]. This classification method mainly focuses on the presentation of symptoms and does not guide the precise treatment of asthma patients. Identifying the phenotype of asthma according to the molecular mechanism can solve this problem to a certain extent.

Asthma can be classified into T2 and nonT2 asthma according to the molecular mechanism of airway inflammation. The former was mainly composed of eosinophils (EOS), mast cell (MC), dendritic cells (DC), and Type 2 innate lymphoid cells (ILC2), which secrete immunoglobulin E (IgE), Interleukin4 (IL4), IL5, IL13, IL33, prostaglandin D2, thymic stromal lymphopoietin (TSLP) and other antibodies and inflammatory factors. NonT2 asthma was involved in the secretion of cytokines

such as IL1, IL6, IL17, CXCL1 and 8, interferonγ (IFNγ), and tumor necrosis factor (TNF)α by inflammatory cells such as neutrophils (NEU) [5]. A number of biomarkers have been identified in broncho alveolar lavage (BAL), peripheral blood, induced sputum, and bronchial biopsy tissue and etc. According to the pathogenesis of different asthma phenotypes, among these samples, peripheral blood can be easily obtained in clinic practice. Thus, we investigate potential biomarkers in peripheral blood for asthma patients, in order to enhance the management and treatment of asthma.
