MRC1 and retinitis pigmentosa: Recent studies have shown that the synthetic progesterone analogue norgestrel reduces the CD68+ M1 phenotype in the rd10 model of retinitis pigmentosa through the presence of progesterone receptors on microglia cells and causes the expression of CD206/MRC1, arginase, etc. [62] Thus, it transforms into an M2 phenotype, ultimately preserving the activity and visual function of retinal photoreceptor cells.