What are lupus patients defficient in?

Deficiency of...: Certain immune proteins, specifically C4 and C2 are associated with increased frequency of sle! also, lupus is female dominant, so estrogen is a factor in both causing and increasing severity of sle!

Immune regulation: Autoimmune disease or allergic disease for that matter arises due to impaired regulation of the immune system wherein the immune system starts to attack one's own tissue. The disease condition is likely partly genetically determined and mostly related to the organ(s) being attacked. Thus the deficiency is in immune regulation. Everything else is just a consequence from it.