One important question is how microglia detect and determine which synapses to eliminate and which ones to spare. Emerging data suggest that microglial cell states, including the synapse phagocytosing ones, are influenced not only by changes in neuronal activity but also by surrounding astrocytes and perivascular macrophages. Further, cell-cell crosstalk influencing synaptic fate can also involve adaptive immune signalling along brain borders. I will discuss potential modulators of microglia-synapse interactions with relevance in neurodegenerative diseases.