IL-2-deficient mice raised under germfree conditions develop delayed mild focal intestinal inflammation

Interleukin-2 (IL-2) amplifies immune stimuli and influences B cell differe ntiation. IL-2-deficient mice spontaneously develop intestinal inflammation if raised under specific pathogen-free (SPF) conditions. We quantitatively determined the aggressiveness and kinetics of gastrointestinal and hepatic inflammation in the presence or absence of viable bacteria in IL-2-deficie nt mice. Breeding colonies were maintained under SPF and germfree (GF) cond itions. Intestinal tissues, serum, and mesenteric lymph nodes were obtained from mice at different ages for blind histological scoring, immunoglobulin measurements, mucosal T cell infiltration, and cytokine secretion. GF IL-2 -/- mice developed mild, focal, and nonlethal intestinal inflammation with delayed onset, whereas the more aggressive inflammation in SPF IL-2 -/- mi ce led to their death between 28 and 32 wk. Periportal hepatic inflammation was equal in the presence or absence of bacterial colonization. Intestinal immunoglobulin secretion decreased significantly by 13 wk of age in IL-2 - /- mice in both GF and SPF environments. In contrast to other genetically e ngineered rodents, IL-2 -/- mice develop mild focal gastrointestinal and ac tive portal tract inflammation in the absence of viable bacteria.