Confocal images showing SphK1 immunoexpression in OX-42 positive amoeboid microglial cells in different age groups. Coronal sections through the forebrain of rats aged 1, 3, 5, 7 and 14 d, showing OX-42 (Aa-Ea) and SphK1 (Ab-Eb) expression in amoeboid microglial cells (AMC) in the corpus callosum. SphK1 immunofluorescence is detected in AMC (Ab, Bb, Cb, Db) as confirmed by OX-42 labeling (Aa, Ba, Ca, Da). Co-expression of OX-42 and SphK1 is seen in merged images in Ac, Bc, Cc and Dc (yellow, white arrows). SphK1 immunofluorescence is evident in AMC in rats aged 1, 3 and 5 d but appears to be weaker at age 7 d; it is absent in 14-d-old rats (Ea-c). Nuclei are stained with DAPI. Scale bar = 50 μm.