MPO and intervertebral disk degenerative disorder: Previous histological studies suggested that immune cells such as CD68+ macrophages and neutrophils may infiltrate into the NP during disc degeneration.19 In the single cell analysis, immunocyte-like populations could be found at all degeneration grades, expressing markers for neutrophils (LYZ and HLA-DRA), macrophages (CD163 and CD68), G-MDSC (ITGAM and MPO) and T cells (TRAC and TRBC2) (SI file 1).