Expression of colony-stimulating factors is altered in lungs of Op/Op mice.

Expression of other CSFs potentially able to compensate for the M-CSF deficiency in Op/Op mice was evaluated in lung homogenates from Op/Op mice and age-matched littermate controls (n = 6/group for each assay; age, 127.1 ± 22.4 days). (A) Evaluation of cytokine protein levels. M-CSF was readily detected in lungs of control but not Op/Op mice. GM-CSF levels were similar in Op/Op and control mice (P = .97). G-CSF levels were slightly increased in Op/Op mice compared with controls (P = .05). IL-3 levels were significantly higher in Op/Op mice (P = .04). (B) Evaluation of IL-3 mRNA levels. Total-lung RNA was purified and evaluated by using IL-3–specific and β-actin–specific oligonucleotide primers. IL-3 mRNA was detected in the lungs of 5 of 6 Op/Op mice but in only 1 of 6 control mice. In contrast, β-actin mRNA levels were similar in all mice. (C) IL-3 bioactivity. Levels of functional IL-3 in BAL of Op/Op and control mice (n = 6/group) were assessed by stimulation of growth of the IL-3–sensitive M-NSF-60 cell line. Cell growth detected by tritium-thymidine incorporation was increased in Op/Op mice compared with controls when M-NFS-60 cells were incubated with BAL from the animals (P < .02).