Ann-Kathrin Weier

Cellular polarization plays a crucial role in regulating immunological processes and is often associated with reorientation of the centrosome. During immune synapse formation, centrosome repositioning in lymphocytes assists in T cell activation. While a single centrosome, consisting of two centrioles, is present in T cells, antigen-presenting cells such as dendritic cells amplify centrioles during maturation and immune activation. How centriole amplification in antigen-presenting cells affects immune synapse formation and T cell activation is unclear. In this study, we combine experimental data with mathematical and computational modelling to provide evidence that extra centrioles in dendritic cells form over-active microtubule organizing centers, which cluster during dendritic cell-T cell interactions and, unlike in T cells, localize close to the cell center. Perturbing either centrosome integrity or centriole numbers and configuration in dendritic cells results in impaired T cell activation. Collectively, our results highlight a crucial role for centriole amplification and optimal centrosome positioning in antigen-presenting cells for controlling T cell responses.

Centrosomes play a crucial role during immune cell interactions and initiation of the immune response. In proliferating cells, centrosome numbers are tightly controlled and generally limited to one in G1 and two prior to mitosis. Defects in regulating centrosome numbers have been associated with cell transformation and tumorigenesis. Here, we report the emergence of extra centrosomes in leukocytes during immune activation. Upon antigen encounter, dendritic cells pass through incomplete mitosis and arrest in the subsequent G1 phase leading to tetraploid cells with accumulated centrosomes. In addition, cell stimulation increases expression of polo-like kinase 2, resulting in diploid cells with two centrosomes in G1-arrested cells. During cell migration, centrosomes tightly cluster and act as functional microtubule-organizing centers allowing for increased persistent locomotion along gradients of chemotactic cues. Moreover, dendritic cells with extra centrosomes display enhanced secretion of inflammatory cytokines and optimized T cell responses. Together, these results demonstrate a previously unappreciated role of extra centrosomes for regular cell and tissue homeostasis.