Are you certain? The immune system detects molecules partly due to their shape, i.e. where binding points are on the proteins. I can imagine it being the case where the immune system's proteins no longer match up with the invader's because of the mirroring.

If you 3d print a mirrored house key, the bitting may line up with the original, but the warding wouldn't fit anymore. I think that's a reasonable analogy to the way proteins match up.