GM-CSF/IL-3–deficient mice show abnormal glucose tolerance tests. Wild-type (n = 8), GM-CSF–deficient (n = 5), IL-3–deficient (n = 6), and GM-CSF/IL-3–deficient (n = 12) mice were injected intraperitoneally with a glucose challenge, and blood (taken from the mice's tails) were serially analyzed. Nine GM-CSF/IL-3–deficient mice showed significantly greater peak blood sugar levels that remained elevated at the end of the test compared with all other groups (P < .001, Wilcoxon rank sum test).