BACH2 restricts NK cell maturation and function, limiting immunity to cancer metastasis

Natural killer (NK) cells are critical to immune surveillance against infections and cancer. Their role in immune surveillance requires that NK cells are present within tissues in a quiescent state. Mechanisms by which NK cells remain quiescent in tissues are incompletely elucidated. The transcriptional repressor BACH2 plays a critical role within the adaptive immune system, but its function within innate lymphocytes has been unclear. Here, we show that BACH2 acts as an intrinsic negative regulator of NK cell maturation and function. BACH2 is expressed within developing and mature NK cells and promotes the maintenance of immature NK cells by restricting their maturation in the presence of weak stimulatory signals. Loss of BACH2 within NK cells results in accumulation of activated NK cells with unrestrained cytotoxic function within tissues, which mediate augmented immune surveillance to pulmonary cancer metastasis. These findings establish a critical function of BACH2 as a global negative regulator of innate cytotoxic function and tumor immune surveillance by NK cells.

Context-dependent effects of IL-2 rewire immunity into distinct cellular circuits

Interleukin 2 (IL-2) is a key homeostatic cytokine, with therapeutic applications in both immunogenic and tolerogenic immune modulation. Clinical use has been hampered by pleiotropic functionality and widespread receptor expression, with unexpected adverse events. Here, we developed a novel mouse strain to divert IL-2 production, allowing identification of contextual outcomes. Network analysis identified priority access for Tregs and a competitive fitness cost of IL-2 production among both Tregs and conventional CD4 T cells. CD8 T and NK cells, by contrast, exhibited a preference for autocrine IL-2 production. IL-2 sourced from dendritic cells amplified Tregs, whereas IL-2 produced by B cells induced two context-dependent circuits: dramatic expansion of CD8+ Tregs and ILC2 cells, the latter driving a downstream, IL-5-mediated, eosinophilic circuit. The source-specific effects demonstrate the contextual influence of IL-2 function and potentially explain adverse effects observed during clinical trials. Targeted IL-2 production therefore has the potential to amplify or quench particular circuits in the IL-2 network, based on clinical desirability.

Positive impact of selective outpatient management of high-risk acute myelogenous leukemia on the incidence of septicemia

BACKGROUND

Curative intent chemotherapy for acute myelogenous leukemia (AML) leads to prolonged severe neutropenia, during which patients are highly susceptible to infection. Traditionally these high-risk patients were treated as inpatients. Our center recently implemented a selective ambulatory management policy for AML patients undergoing chemotherapy.

MATERIALS AND METHODS

A retrospective analysis was conducted to assess the occurrence of septicemia in AML patients treated over a 5 years period with curative intent chemotherapy. This review encompasses a change in policy from primarily inpatient care to selective outpatient management coupled with prophylactic antibiotic therapy.

RESULTS

A total of 294 patients, receiving 623 cycles of chemotherapy were identified. A significant decrease in septicemia was observed from the inpatient to outpatient cohort (22% to 13% P < 0.05), which correlated with the shift towards outpatient treatment of consolidation cycles. A shift from Gram-negative to Gram-positive organisms as the cause of septicemia was also detected in the outpatient cohort, likely due to the introduction of ciprofloxacin prophylaxis. No significant emerging resistance and no septicemia-related mortality were noted in the outpatient cohort.

CONCLUSION

The observed decrease in the incidence of septicemia in the ambulatory cohort adds supportive evidence to the feasibility of selective outpatient management of AML patients with respect to infectious complications.