Immunofluorescence labeling of left lung tissue for evidence of complement protein 3 (C3), complement protein 4 (C4), and fatty acid binding protein-4 (FABP4). SU/hyp lung tissue labeled for C3 (A, B), C4 (C), and FABP4 (G). Control lung tissue labeled for C3 (D), C4 (E), and FABP4 (H). F, C3 and C4 immunoglobulin G (IgG) 1 isotype control; I, FABP IgG isotype control. C3/C4: red; autofluorescence: green; FABP4: purple. A, C–I, original magnification ×10; B, original magnification ×20.