Investigation of PD-1 expression in sarcoidosis and healthy control cohorts revealed an average of 4.2% PD-1+CD4+ sarcoidosis T cells while the average percentage of PD-1+CD4+ T cells in the healthy control cohort was approximately 1.6% (Figures 4(a) and 4(b); p < 0.0001). This evidence concerns the gene CD4 and sarcoidosis.