Sexual dimorphism of lung immune-regulatory units imprint biased pulmonary fibrosis.

Pulmonary fibrosis (PF) is sexually dimorphic, with a relatively high prevalence and severity in males; however, the mechanism remains unclear. Our study revealed pronounced sexual dimorphism of immune cell genes in the lung, among which grancalcin (GCA) showed profound sex differences. GCA was produced by lung-infiltrating bone marrow macrophages triggered by heightened inflammation in the lung. However, a unique HTR2C⁺ alveolar macrophage population enriched in female lungs metabolically reprogramed bone marrow-derived macrophages and constrained local GCA amplification. As a novel chemokine, GCA bound to protein tyrosine phosphatase receptor type T (PTPRT) in Th17 cells and facilitated pathogenic lung infiltration by activating the ROCK1-MLC pathway, thus aggravating lung fibrosis. Notably, both GCA and Th17 cells abundantly accumulated in lung biopsies from male PF patients but not in those from female patients. GCA-neutralizing antibodies in combination with pirfenidone, a prescribed medication for treating fibrosis, provided superior effectiveness and survival rates against PF compared with treatment with pirfenidone alone. Overall, our findings reveal that sex-biased lung fibrosis is shaped by lung immune-regulatory units, which could be targeted to limit lung fibrosis.