Deletion of IL-4Ralpha on CD4 T cells renders BALB/c mice resistant to Leishmania major infection

Effector responses induced by polarized CD4⁺ T helper 2 (Th2) cells drive nonhealing responses in BALB/c mice infected with Leishmania major. Th2 cytokines IL-4 and IL-13 are known susceptibility factors for L. major infection in BALB/c mice and induce their biological functions through a common receptor, the IL-4 receptor α chain (IL-4Rα). IL-4Rα–deficient BALB/c mice, however, remain susceptible to L. major infection, indicating that IL-4/IL-13 may induce protective responses. Therefore, the roles of polarized Th2 CD4⁺ T cells and IL-4/IL-13 responsiveness of non-CD4⁺ T cells in inducing nonhealer or healer responses have yet to be elucidated. CD4⁺ T cell–specific IL-4Rα (Lck^creIL-4Rα^−/lox) deficient BALB/c mice were generated and characterized to elucidate the importance of IL-4Rα signaling during cutaneous leishmaniasis in the absence of IL-4–responsive CD4⁺ T cells. Efficient deletion was confirmed by loss of IL-4Rα expression on CD4⁺ T cells and impaired IL-4–induced CD4⁺ T cell proliferation and Th2 differentiation. CD8⁺, γδ⁺, and NK–T cells expressed residual IL-4Rα, and representative non–T cell populations maintained IL-4/IL-13 responsiveness. In contrast to IL-4Rα^−/lox BALB/c mice, which developed ulcerating lesions following infection with L. major, Lck^creIL-4Rα^−/lox mice were resistant and showed protection to rechallenge, similar to healer C57BL/6 mice. Resistance to L. major in Lck^creIL-4Rα^−/lox mice correlated with reduced numbers of IL-10–secreting cells and early IL-12p35 mRNA induction, leading to increased delayed type hypersensitivity responses, interferon-γ production, and elevated ratios of inducible nitric oxide synthase mRNA/parasite, similar to C57BL/6 mice. These data demonstrate that abrogation of IL-4 signaling in CD4⁺ T cells is required to transform nonhealer BALB/c mice to a healer phenotype. Furthermore, a beneficial role for IL-4Rα signaling in L. major infection is revealed in which IL-4/IL-13–responsive non-CD4⁺ T cells induce protective responses.

Leishmaniasis is a disease induced by a protozoan parasite and transmitted by the sandfly. Several forms of infection are identified, and the different diseases have wide-ranging symptoms from localized cutaneous sores to visceral disease affecting many internal organs. Animal models of human cutaneous leishmaniasis have been established in which disease is induced by infecting mice subcutaneously with Leishmania major. Different strains of inbred mice have been found to be susceptible or resistant to L. major infection. “Healer” C57BL/6 mice control infection with transient lesion development. The protective response to infection in this strain is dominated by type 1 cytokines inducing parasite killing by nitric oxide. Conversely, “nonhealer” BALB/c mice are unable to control infection and develop nonhealing lesions associated with a dominant type 2 immune response driven by cytokines IL-4 and IL-13. However, mice deficient in IL-4/IL-13 signaling are not protected against development of cutaneous leishmaniasis. Here we describe a BALB/c mouse where the ability to polarize to a dominant type 2 response is removed by cell-specific deletion of the receptor for IL-4/IL-13 on CD4⁺ T cells. These mice are resistant to L. major infection similar to C57BL/6 mice, which highlights the role of T helper 2 cells in driving susceptibility and the protective role of IL-4/IL-13 signaling in non-CD4⁺ T cells in BALB/c mice.

Polymorphisms in the IL4 and IL4RA genes in Colombian patients with rheumatoid arthritis

OBJECTIVE

Rheumatoid arthritis (RA) is considered a Th1-driven disease. Interleukin 4 (IL-4) binds to its receptor, promoting Th2 differentiation and limiting Th1 responses, but its role in the pathogenesis of RA is conflicting. We analyzed 2 polymorphisms of the IL4 gene and 4 polymorphisms of the IL4RA gene in patients with RA and in a control population, as well as rheumatoid factor (RF) seropositivity, titers of RF, and history of replacement joint surgery among patients with RA.

METHODS

The study population consisted of 102 patients with RA and 102 matched healthy controls. Genotyping of IL4 -590, IL4RA +148, +1124, +1218, and +1902 was determined by restriction fragment length polymorphism-polymerase chain reaction (PCR) and sequence-specific primer-PCR. IL4 variable number tandem repeat polymorphism was determined by direct amplification.

RESULTS

The IL4 -590TT genotype was significantly more frequent in patients with RA than in controls (p = 0.018, OR 3.34, 95% CI 1.08-11.04). The IL4RA +148A allele was significantly associated with the presence of RF (p = 0.0019, OR 2.55, 95% CI 1.55-4.86) and a history of articular joint replacement (p = 0.024, OR 2.08, 95% CI 1.04-4.18). The IL4RA +1902G allele was more frequently seen in patients with RA and high RF titers (p = 0.00067, OR 4, 95% CI 1.64-9.93).

CONCLUSION

Highly complex pathways lead to the development of RA and may not be similar in all patients. Our findings of higher frequency of IL4 and IL4RA genotypes and alleles with RA, presence of RF, RF titers, and history of articular joint replacement support the polygenic expression of RA and the likely role of IL-4 in influencing its initiation and development.

The role of platelet adhesion receptor GPIbalpha far exceeds that of its main ligand, von Willebrand factor, in arterial thrombosis

GPIbalpha binding to von Willebrand factor (VWF) exposed at a site of vascular injury is thought to be the first step in the formation of a hemostatic plug. However, our previous studies in VWF-deficient mice demonstrated delayed but not absent arterial thrombus formation, suggesting that, under these conditions, GPIbalpha may bind other ligands or that a receptor other than GPIbalpha can mediate platelet adhesion. Here, we studied thrombus formation in transgenic mice expressing GPIbalpha in which the extracellular domain was replaced by that of the human IL-4 receptor (IL4Ralpha/GPIbalpha-tg mice). Platelet adhesion to ferric chloride-treated mesenteric arterioles in IL4Ralpha/GPIbalpha-tg mice was virtually absent in contrast to avid adhesion in WT mice. As a consequence, arterial thrombus formation was inhibited completely in the mutant mice. Our studies further show that, when infused into WT recipient mice, IL4Ralpha/GPIbalpha-tg platelets or WT platelets lacking the 45-kDa N-terminal domain of GPIbalpha failed to incorporate into growing arterial thrombi, even if the platelets were activated before infusion. Surprisingly, platelets lacking beta3 integrins, which are unable to form thrombi on their own, incorporated efficiently into WT thrombi. Our studies provide in vivo evidence that GPIbalpha absolutely is required for recruitment of platelets to both exposed subendothelium and thrombi under arterial flow conditions. Thus, GPIbalpha contributes to arterial thrombosis by important adhesion mechanisms independent of the binding to VWF.