Susceptibility of interleukin-2-deficient mice to Toxoplasma gondii is associated with a defect in the production of gamma interferon.
Costimulation through the B7-CD28 interaction is an important second signal for T-cell activation, and previous studies have shown that CD28(-/-) mice infected with Toxoplasma gondii generate suboptimal CD4(+) T-cell responses, associated with a defect in production of the T-cell growth factor interleukin-2 (IL-2). To address the role of IL-2 in the expansion of T cells during toxoplasmosis, IL-2(-/-) mice were infected with T. gondii and their ability to generate a protective T-cell response was assessed. Although IL-2(-/-) mice produced normal levels of IL-12p40, they had reduced levels of gamma interferon (IFN-gamma) in serum, had an increased parasite burden, and succumbed to infection with T. gondii within 20 days. Fluorescence-activated cell sorter analysis revealed that, although uninfected IL-2(-/-) mice had an increased number of activated T cells compared with uninfected IL-2(+/+) mice, following infection they were unable to further upregulate this population. Examination of the ability of splenocytes from uninfected and infected mice to produce IFN-gamma revealed that IL-2(-/-) mice were hyporesponsive to stimulation with anti-CD3 or parasite antigen compared with wild-type mice, and the addition of IL-2 alone or in combination with IL-12 or stimulation with phorbol myristate acetate and ionomycin did not restore the production of IFN-gamma. Together, these studies reveal that IL-2(-/-) mice are unable to generate a protective IFN-gamma response following infection with T. gondii and suggest that IL-2(-/-) mice have an intrinsic defect in their ability to activate and expand IFN-gamma-producing T cells required for resistance to T. gondii.
Villegas
Eric N
EN
Department of Pathobiology, University of Pennsylvania, School of Veterinary Medicine, Philadelphia 19104-6050, USA.
Lieberman
Linda A
LA
Carding
Simon R
SR
Hunter
Christopher A
CA
D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000187:drug effects / Q000276:immunology; D005260:Female; D007371:Interferon-gamma / Q000096:biosynthesis*; D018664:Interleukin-12 / Q000494:pharmacology; D053762:Interleukin-12 Subunit p40; D007376:Interleukin-2 / Q000172:deficiency* / Q000235:genetics / Q000494:pharmacology; D008213:Lymphocyte Activation; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D021122:Protein Subunits; D015398:Signal Transduction; D013154:Spleen / Q000276:immunology; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology; D014122:Toxoplasma / Q000472:pathogenicity; D014124:Toxoplasmosis, Animal / Q000209:etiology* / Q000235:genetics / Q000276:immunology
D053762:Interleukin-12 Subunit p40; D007376:Interleukin-2; D021122:Protein Subunits; D018664:Interleukin-12; D007371:Interferon-gamma