Fig. 2

Quantitative distribution of C1q immunolabeling in aged macaque dlPFC layer III and labeling in glial profiles. The prevalence of C1q labeling in asymmetric synapses in dlPFC layer III neuropil, expressed as a percentage (a). Ultrastructural localization of C1q within different cellular elements in aged monkey dlPFC layer III. The percentage of immunoperoxidase labeling (mean ± SEM) for C1q across glia, dendritic shafts, dendritic spines, and axon terminals in aged macaque dlPFC layer III, N = 3 aged rhesus macaques (b). Immunolabeling for C1q is present along the plasma membrane and within the intracellular space of glial processes. c–e C1q labeling is observed in glial leaflets ensheathing the axospinous glutamatergic-like asymmetric synapses. c C1q labeling is observed in glial leaflets ensheathing a synaptic triad or dually innervated spine, receiving a glutamatergic-like asymmetric synapse with the axon terminal containing spherical neurotransmitter vesicles and a symmetric synapse (black arrowhead) with the axon terminal containing pleomorphic neurotransmitter vesicles (likely GABA or dopamine). The smooth endoplasmic reticulum (SER) spine apparatus is pseudocolored in pink. f C1q labeling is also seen in glial leaflets ensheathing axodendritic glutamatergic-like synapses. Synapses are between black arrows. Color-coded arrowheads (purple) point to C1q immunoreactivity. The profiles are pseudocolored for clarity. Ax, axon; Sp, spine; Den, dendrite; Mit, mitochondria; G, glia. Scale bars, 200 nm