资源环境科技发展态势分析平台

Following its flyby and first imaging of the Pluto-Charon binary, the New Horizons spacecraft visited the Kuiper belt object (KBO) 2014 MU69 (also known as (486958) Arrokoth). The imaging showed MU69 to be a contact binary that rotates at a low spin period (15.92 hours), is made of two individual lobes connected by a narrow neck and has a high obliquity (about 98 degrees)(1), properties that are similar to those of other KBO contact binaries inferred through photometric observations(2). However, all scenarios suggested so far for the origins of such configurations(3-5) have failed to reproduce these properties and their probable frequent occurrence in the Kuiper belt. Here we show that semi-secular perturbations(6,7) operating on only ultrawide KBO binaries close to their stability limit can robustly lead to gentle, slow binary mergers at arbitrarily high obliquities but low rotational velocities, reproducing the characteristics of MU69 and other similar oblique contact binaries. Using N-body simulations, we find that approximately 15 per cent of all ultrawide binaries with a cosine-uniform inclination distribution(5,9) are likely to merge through this process. Moreover, we find that such mergers are sufficiently gentle to deform the shape of the KBO only slightly. The semi-secular contact binary formation channel not only explains the observed properties of MU69, but may also apply to other Kuiper belt or asteroid belt binaries and in the Solar System and extra-solar moon systems.

The high obliquity and low rotation period of the Kuiper belt object (2014) MU69 and other similar contact binaries is successfully reproduced from the collision and post-collision characteristics of initially wide binaries.

Checkpoint blockade therapies that reactivate tumour-associated T cells can induce durable tumour control and result in the long-term survival of patients with advanced cancers(1). Current predictive biomarkers for therapy response include high levels of intratumour immunological activity, a high tumour mutational burden and specific characteristics of the gut microbiota(2,3). Although the role of T cells in antitumour responses has thoroughly been studied, other immune cells remain insufficiently explored. Here we use clinical samples of metastatic melanomas to investigate the role of B cells in antitumour responses, and find that the co-occurrence of tumour-associated CD8(+) T cells and CD20(+) B cells is associated with improved survival, independently of other clinical variables. Immunofluorescence staining of CXCR5 and CXCL13 in combination with CD20 reveals the formation of tertiary lymphoid structures in these CD8(+)CD20(+) tumours. We derived a gene signature associated with tertiary lymphoid structures, which predicted clinical outcomes in cohorts of patients treated with immune checkpoint blockade. Furthermore, B-cell-rich tumours were accompanied by increased levels of TCF7(+) naive and/or memory T cells. This was corroborated by digital spatial-profiling data, in which T cells in tumours without tertiary lymphoid structures had a dysfunctional molecular phenotype. Our results indicate that tertiary lymphoid structures have a key role in the immune microenvironment in melanoma, by conferring distinct T cell phenotypes. Therapeutic strategies to induce the formation of tertiary lymphoid structures should be explored to improve responses to cancer immunotherapy.

The co-occurrence of tumour-associated CD8(+) T cells and CD20(+) B cells, and the formation of tertiary lymphoid structures, are linked with improved survival in cohorts of patients with metastatic melanoma.