Biological Analyses-Derived Translational Findings in the T Cell Receptor Alpha Chain Knockout Mouse as an Experimental Model for Ulcerative Colitis

Inflammatory bowel disease (IBD) is a group of chronic inflammatory disorders that affects many individuals throughout their lives. Ulcerative colitis (UC) and Crohn’s disease (CD) are two major forms of IBD. Until the early 1990s, a murine model of spontaneous chronic colitis was unavailable. As a major breakthrough in the basic research field of IBD, three genetically manipulated murine chronic colitis models, including interleukin (IL)-2 knockout (KO), IL-10 KO, and T cell receptor alpha chain (TCRα) KO models, were established in 1993. Since then, complicated immunobiological mechanisms during the development of UC have been gradually discovered by utilizing a wide variety of murine models of IBD, including the TCRα KO mouse model. In particular, it has been recognized that four major factors, including enteric, environmental, and immunological factors as well as enteric microbiota are highly and mutually involved in the pathogenesis of UC. As a pioneer of the TCRα KO murine model of UC, our group has identified that the interactions between the unique TCRα-β+ T cell population and antigen-presenting cells, including dendritic cells and B cells, play a key role for the development and regulation of UC-like chronic colitis, respectively. Here we have summarized clinically proven pathogenic and regulatory factors which have been identified by this novel TCRα KO murine model of UC in the past nearly three decades.

A novel case of homozygous IFNAR1 deficiency with haemophagocytic lymphohistiocytosis

We present a case of complete deficiency of the Interferon alpha/beta receptor alpha chain (IFNAR1) in a child with fatal systemic hyperinflammation, apparently provoked by live-attenuated viral vaccination. Such pathologic hyperinflammation, fulfilling criteria for haemophagocytic lymphohistiocytosis, is an emerging phenotype accompanying inborn errors of type I interferon immunity.

Interleukin-2 Receptor Alpha Chain, Also Called CD25, Is a Potential Target in Acute Lymphoblastic Leukemia

Background: Acute lymphoblastic leukemia (ALL) is a molecularly heterogeneous disease originating from clonal proliferation of precursor B-lineage cells. In adults, ALL diagnosis is still associated with a dismal prognosis due to the lack of specific targeted therapies. This study was designed to investigate the expression of interleukin-2 receptor alpha chain CD25 in B-ALL and its biological significance, especially following the availability of specific CD25 targeting compounds. Methods:The expression of IL2RA (CD25 gene) was detected by flow cytometry (FC), immunohistochemistry and Western blot analysis, in 25 newly diagnosed ALL patients, both Philadelphia positive (12 patients) and Philadelphia negative (13 patients). Similarly, CD25 expression was assessed in four B-ALL commercially available cell lines. Infection with shRNA specifically directed against CD25 was used to evaluate apoptosis induction and cell cycle arrest in primary B-ALL cells established from two patients. Results:Our data suggest that ALL, and in particular Ph-positive ALL, aberrantly expresses the interleukin-2 receptor alpha chain, CD25. Whereas normal B cells display low amounts of CD25, primary ALL cells and ALL cell lines (over)-express CD25. While the high frequency of CD25 on the surface of many different hematological tumor cells has been established and confirmed in our study, there is little investigation focusing on the significance of CD25 expression. Indeed, CD25 may be present on ALL cells and enable oncogenic signaling pathways. In such respect, we observed that CD25 silencing in primary cells promotes cell cycle arrest and apoptosis induction. While these data support the rational to target CD25, ALL cells did not appear to be in-vitro sensitive to basiliximab, an antibody able to target the Il2RA, but in-vivo investigations are needed to better assess the effects of this therapeutic approach in ALL context. Conclusions:We concluded that CD25 expression is elevated in patients with B-ALL. Our results also demonstrate that CD25 silencing induces cell cycle arrest and apoptosis. The latter result has important implications from a therapeutic point of view. Targeting CD25 receptor with anti-CD25 antibodies or peptide mimetics could be an effective strategy for targeting leukemic cells. Additionally, high CD25 expression could be exploited for the development of CAR-T therapy Disclosures Saglio: Roche:Research Funding;Pfizer:Research Funding;Incyte:Research Funding;Novartis:Research Funding;Ariad:Research Funding;Bristol-Myers Squibb:Research Funding.

Membrane-associated RING-CH (MARCH) proteins down-regulate cell surface expression of the interleukin-6 receptor alpha chain (IL6Rα)

Interleukin 6 (IL6) is a cytokine that regulates a number of important immune and inflammatory pathways. We used the ability of IL6 to inhibit the clonal proliferation of the mouse M1 myeloid leukemia cell line in agar to positively screen a cDNA expression library for proteins that inhibited IL6 activity. We found three clones completely resistant to IL6 that contained the cDNA for the Membrane-Associated RING-CH E3 ubiquitin ligase MARCH2. MARCH2 is a member of a family of membrane-bound E3 ubiquitin ligases that target cell surface receptors for degradation. MARCH2 overexpressing M1 clones retained responsiveness to the related cytokines leukemia inhibitory factor and oncostatin M and we showed that its inhibitory effect was a result of selective down-regulation of the IL6 receptor alpha chain and not the shared receptor subunit, gp130 or other signalling molecules. This activity of MARCH2 was also shared with related proteins MARCH4, MARCH9 and an isoform of MARCH3. The transmembrane domains and C-terminal domains, as well as a functional RING domain, of MARCH proteins were all required for substrate recognition and down-regulation. Genetic deletion of individual MARCH proteins in mice had no or little effect on IL6Rα levels but combined deletions of MARCH2,3 and 4 displayed elevated steady-state levels of IL6Rα in selected haemopoietic cell subsets including CD8+ and CD4+ T cells. These studies extend the potential immunosuppressive roles of MARCH proteins to include down-regulation of IL6 inflammatory responses.