A Th2 immune response is central to allergic airway inflammation, which afflicts millions worldwide. However, the mechanisms that augment GATA3 expression in an antigen-primed developing Th2 cell are not well understood. Here, we describe an unexpected role for Blimp-1, a transcriptional repressor that constrains autoimmunity, as an upstream promoter of GATA3 expression that is critical for Th2 cell development in the lung to inhaled but not systemically delivered allergens but is dispensable for TFH function and IgE production. Mechanistically, Blimp-1 acts through Bcl6, leading to increased GATA3 expression in lung Th2 cells. Surprisingly, the anti-inflammatory cytokine IL-10, but not the pro-inflammatory cytokines IL-6 or IL-21, is required via STAT3 activation to up-regulate Blimp-1 and promote Th2 cell development. These data reveal a hitherto unappreciated role for an IL-10–STAT3–Blimp-1 circuit as an initiator of an inflammatory Th2 response in the lung to allergens. Thus, Blimp-1 in a context-dependent fashion can drive inflammation by promoting rather than terminating effector T cell responses.

STAT3-mediated Blimp-1 induction in T cells antagonizes STAT5’s role in promoting cell cycle and cell survival genes.

The transcriptional repressor Blimp-1 acts via a pro-inflammatory IL-10-17 STAT3 axis as a critical positive regulator of Th2 cells in the lung in response to 18 allergens driving pathophysiology associated with asthma disease. 19 20 Abstract 21 A Th2 immune response is central to allergic airway inflammation, which afflicts millions 22worldwide. However, the mechanisms that augment GATA3 expression in an antigen-23 to allergens. Thus, Blimp-1 in a context-dependent fashion can drive inflammation by 33 promoting rather than terminating effector T cell responses. 34 35 1997). However, the signals that support this process in vivo are still not well death, suggesting Blimp-1 also controls effector responses by limiting effector cell 70 numbers directly (Poholek et al., 2016). 71Our previous studies showed that disrupting Blimp-1 in T cells increased Th2 responses 72 in a worm antigen model. Therefore, we hypothesized that T cell specific deficiency of 73Blimp-1 in an allergic airway inflammation model would lead to increased expansion of 74 effector cells and more severe disease due to increased Th2 responses. Unexpectedly, 75we found that T cell specific Blimp-1 deficiency protected mice from the development of 76 allergic lung inflammation and Th2 cells in the lung were severely reduced. STAT3 via 77 IL-10 was required for Blimp-1 expression and Th2 cell development in this model, 78suggesting IL-10 may play an unexpected role in supporting Th2 cell differentiation. 79Mechanistically, our data supports an intrinsic role for Blimp-1 mediated repression of 80 Bcl6, which in turn can repress GATA3. Thus, Blimp-1 indirectly supports Th2 81 differentiation by promoting GATA3 expression. These data identify a new context-82 dependent role for Blimp-1 in T cells that is essential for the full development of allergic 83 lung disease, highlighting a previously unappreciated pathway with potential therapeutic 84 targets for the treatment of asthma disease. 85 86Results 87 Blimp-1 in T cells promotes allergic airway inflammation 88Blimp-1 controls effector T cell responses and constrains autoimmunity (Crotty et al., 89 2010; Poholek et al., 2016). We reasoned that during a house dust mite (HDM) induced 90 model of allergic lung disease, the absence of Blimp-1 in T cells would drive increased 91 effector T cells and exacerbate disease. To test this, we compared mice in which Blimp-92 the lung and mLN (Fig 1E,F, S1C), suggesting that the absence of Blimp-1 in T cells 130 resulted in a concomitant increase in Bcl6. Together, these data suggest that Blimp-1 131 plays a surprising and critical role in driving the differentiation of Th2 cells in response to 132 inhaled allergens that is necessary for resulting inflammation in the lung tissue. 133 134 IgE responses are Blimp-1 independent 135A hallmark of type2 driven allergic responses is the presence of high levels of circulating 136IgE. In contrast to the decrease in type2 immunity observed in the lungs of Blimp-1 CD4Cre 137 animals (reduced Th2 cells and eosinophils in BAL)...

Asthma is a T cell-mediated chronic inflammatory lung disease that is thought of as a type 2/Th2 disease, yet precisely how Th2 cell development in the lung is initiated is unknown. Blimp-1 is a transcriptional repressor that regulates effector T cell responses to constrain T cell-mediated autoimmunity. We describe Blimp-1 as an unexpected regulator of allergen-induced airway inflammation that is critical to promote Th2 cell development in the lung and subsequent airway inflammation. Using a house dust mite (HDM) antigen model to drive allergic lung disease, we show that the T cell specific absence of Blimp-1 leads to reduced lung inflammation, a significant decrease in eosinophil recruitment to the lung tissue, and a near absence of Th2 cells in the lung. Intriguingly, Th1 and Th17 responses are intact, suggesting Blimp-1 is specifically required for Th2 differentiation in this model. Furthermore, despite a lack of Th2 cells in the lung, IgE responses are intact, dissociating IL-4-mediated antibody driven responses from Th2 cells in the lung. Bcl6 expression is increased in both the draining lymph node and lung and using T cell specific Bcl6 and Blimp-1 double deficient mice, we find that Th2 cells are restored when Bcl6 is deleted in addition to Blimp-1. Bcl6 is a potent repressor of GATA3, suggesting Blimp-1 acts to indirectly promote GATA3 expression by suppression of Bcl6. Furthermore, we show that STAT3 signaling in T cells is responsible to upregulate Blimp-1 and subsequent Th2 development, implicating this pathway as a possible therapeutic target. Taken together, our data suggests Blimp-1 plays an unexpected and context-dependent role in allergic lung inflammation to promote Th2 cell differentiation and subsequent lung disease.

Blimp-1 is a transcription factor known to have critical roles in multiple cell types including B, T and NK cells. However, its expression and function in non-NK innate lymphoid cell populations have not been well studied. To examine the expression and function of Blimp-1 in group 2 innate lymphoid cells, we analyzed several models of type 2 immunity. We found that Blimp-1 is not highly expressed in ILC2s at steady-state, however it is induced under specific stimulation conditions. Especially, Blimp-1 expression is substantially increased in house dust mite (HDM) activated mouse lung over time. In vivo and in vitro ILC2 stimulation with cytokines show that both IL-33 and IL-10 can induce Blimp-1 expression, indicating Blimp-1 is driven by multiple signals. Interestingly, HDM driven Blimp-1 expressing ILC2 have a distinct transcriptional program compared to classically-activated ILC2s treated with IL-25 and IL-33. ILC2 that express Blimp-1 predominantly lack type 2 cytokine expression, suggesting Blimp-1 plays a role independent of cytokine production and may represent a unique functional state of ILC2 cells in settings of chronic antigen including allergic disease. Our findings therefore demonstrate a previously unappreciated Blimp-1 expressing ILC2 population with distinct features that may be important for type 2 mediated disease.