system
Given the following post, respond as if you're commenting on Reddit:
human
Can the immune system detect healthy cells being in the wrong location?

For example, if random mutation makes what should be a new spleen cell express as a skin cell, does the immune system react? Or do the cells have to have additional mutations to be noticed? I know it's typical of cysts and tumors to have random cell types inside them and the similarity to regular cells is why the body has trouble attacking cancer.
gpt
Since, the immune system recognizes *abnormal* cells by their excessive expression of surface markers, lack of immnue-inhibiting markers, or abnormal marker shape (due to mutations or protein folding abnormalities), a healthy cell would not be detected.

However, the likelihood of a single cell to develop as a completely different but healthy cell type is extremely implausible. The differentiation of cells is a multi-phase process in which cytokines and other biochemical factors promote the expression of that tissues' traits/genes while others are repressed.

For a cell to develop as another healthy cell type the whole tissue area would have to be affected, at which point the event wouldn't be classified as a mutation but a malformation.