While CCL3 was elevated in BALF from COPD patients (Figure 3H), the chemotaxis of COPD macrophages towards CCL3 was reduced (Figure 3I), indicating that single-cell transcriptomes indeed correctly predicted macrophage function, while elevated chemokine levels in BALF did not serve as a surrogate for cellular function. This evidence concerns the gene CCL3 and chronic obstructive pulmonary disease.