CTLA4 and idiopathic pulmonary fibrosis: To determine the expression of CTLA4 at single-cell resolution in CD8+ T cells, we quantitated transcript levels of CTLA4 in this cell population and compared relative levels of expression in fibrotic regions (enriched for COL5A2) compared with less fibrotic regions (enriched for AGER); this analysis showed significantly higher CTLA4 levels in CD8+ T cells localized to fibroblastic foci than in regions of the IPF lung without distinct foci (Figure 3D; bar graph representing fibrotic regions and minimally fibrotic regions, 5 regions each from 3 different IPF lungs; n = 15 per group).