According to the World Health Organization, over 360 million people worldwide suffer from some form of hearing loss. Loss of hair cells is the most common cause of sensorineural hearing loss. Spiral ganglion neurons (SGNs), which transmit acoustic signals from hair cells to the brain, gradually die after hair cell death. Surrounding these neurons are satellite glial cells, which is known to myelinate the neuronal cell body in many animals including rodents. The loss of SGNs can significantly limit the effectiveness of cochlear implants and other types of hearing aids.  Microarray and qPCR results done in our lab showed that there is a significant upregulation of genes associated with cellular immunity when spiral ganglia are dying (39% of genes associated with cellular immunity double in expression in deaf vs. hearing mice).  We hypothesized that there was infiltration of immune cells after deafening. To label immune cells, we used antibody against CD45 antigen (aka Leukocyte common antigen), which is expressed in all immune cells. In both hearing and deaf animals, CD45 was expressed in the cells adjacent to the neurons and formed a halo around the neurons (which was labeled with NF200). CD45 labeling co-localized with Connexin29 and S100 labeling which implies that these are satellite glial cells. Our results suggest that satellite glial cells in spiral ganglia might be immune competent cells and could play a role in the immune activation that we observe after deafening.