In addition to the aforementioned TREM2-APOE pathways, microglia in ALS have been shown to exhibit a pro-inflammatory phenotype with the expression of genes such as secreted phosphoprotein 1, Ccl3, and Ccl4, which, like Ccl2, promote the infiltration of peripheral monocytes [105]. Here, APOE is linked to amyotrophic lateral sclerosis.