Autoimmune disorders (AD)are ignited by the human body due to a unstable immune reaction against its personal tissues. The inflammation & damage of tissues by its own antibodies leads autoimmune disorder. A.D. is mainly of two common types -- systemic autoimmune diseases and localized diseases.
In a A.D., a bacteria or virus generates an immune reaction, and the T-cells or antibodies produced against it target normal cells as they have some fraction of their configuration that bear a resemblance to a part of the arrangement of the contaminating microorganism. All cells carry a genetic marker, the cells of the left side have a different marker, so you may see Parkinsonism, ALS, MS, Fibromyalgia begin on one side of the body. So get rid of the bug and you can stop the immune attack by using IVIg.

You can see above that pale shadows are the areas where Myelin has been lost and if you see the thick round rings below are the myelin sheaths. The thin rings are the places where myelin has been lost.
This is the pathology in CIDP and GBS , polyneuropathy, diabetic neuropathy and in the brain in MS (Mutiple Sclerosis).
Pathology in a disease process is study at cellular level. In nearly all autoimmune diseases one will see inflammation. The inflammatory cells will increase, tissue-infiltrating cells in autoimmune inflammation include multiple different cell types like lymphocytes, nonspecific phagocytes, granulocytes, fibroblasts, and others. Also, the attacked tissue responds to the injury with a series of events counteracting or amplifying tissue destruction.
Generally what is seen in a slide is inflammatory cells with atrophic cells, some cells due to inflammation may enlarge in size. This is the hallmark of autoimmune diseases.