Copycat innate lymphoid cells dampen gut inflammation

Role of rare immune cells in common variable immunodeficiency

Common variable immunodeficiency disorder (CVID) is a heterogeneous disorder and the most common symptomatic antibody deficiency disease characterized with hypogammaglobulinemia and a broad range of clinical manifestations. Multiple genetic, epigenetic, and immunological defects are involved in the pathogenesis of CVID. These immunological defects include abnormalities in the number and/or function of B lymphocytes, T lymphocytes, and other rare immune cells. Although some immune cells have a relatively lower proportion among total immune subsets in the human body, they could have important roles in the pathogenesis of immunological disorders like CVID. To the best of our knowledge, this is the first review that described the role of rare immune cells in the pathogenesis and clinical presentations of CVID.

The Regulatory Function of CCR9+ Dendritic Cells in Inflammation and Autoimmunity

Chemokine receptor CCR9 is a G protein–coupled receptor and expressed on several types of immune cells, including dendritic cells (DCs), CD4⁺ T cells, and B cells. CCR9 drives the migration of immune cells to gradients of its cognate ligand CCL25. The chemokine CCL25 is mostly produced by gut and thymic epithelial cells. Gut- and thymic-homing DCs are known to express CCR9, and these cells are predominantly localized in the gut lining and thymus. CCR9⁺ DCs are implicated in regulating inflammation, food allergy, alloimmunity, and autoimmunity. Differential interaction of CCR9⁺ DCs with lymphoid and myeloid cells in the thymus, secondary lymphoid tissues, and mucosal sites offer crucial insights to immune regulation. In this review, we examine the phenotypes, distributions, and interactions of CCR9⁺ DCs with other immune cells, elucidating their functions and role in inflammation and autoimmunity.

Reduced numbers of circulating group 2 innate lymphoid cells in patients with common variable immunodeficiency

Recent studies identified an emerging role of group 2 and 3 innate lymphoid cells (ILCs) as key players in the generation of T-dependent and T-independent antibody production. In this retrospective case-control study, CD117⁺ ILCs (including the majority of ILC2 and ILC3) were reduced in patients with common variable immunodeficiency (CVID). The reduction in CD117⁺ ILCs was distinctive to CVID and could not be observed in patients with X-linked agammaglobulinemia. Patients with a more pronounced reduction in CD117⁺ ILC numbers showed significantly lower numbers of peripheral MZ-like B cells and an increased prevalence of chronic, non-infectious enteropathy. Subsequent phenotyping of ILC subsets in CVID revealed that the reduction in CD117⁺ ILC numbers is due to a reduction in ILC2 numbers. In vitro expansion of CVID ILC2 in response to IL-2, IL-7, IL-25 and IL-33 was impaired. Furthermore, upregulation of MHCII and IL-2RA in response to IL-2, IL-7, IL-25 and IL-33 was impaired in CVID ILC2. Thus, our results indicate a dysregulation of ILC subsets with a reduction in ILC2 numbers in CVID, however, further studies are needed to explore whether ILC abnormalities are a primary finding or secondary to disease complications encountered in CVID.