Our decision tree analysis demonstrated that the best clustering variables were the CD103+CD4+/CD4+ ratio and ThNaive percentages in peripheral blood, as well as the CD103+CD4+/CD4+ ratio and Tfh percentages in the alveolar compartment, sustaining the potential role of these immunological findings in the characterisation of sarcoidosis patients. The gene discussed is CD4; the disease is sarcoidosis.