Except for the Vitamines E, D, K and A, Vitamines are takes up in a controlled way so you cant really overdose them. Overdosing VitA can cause blindness So thats no joke either.

Im no expert on supplements but I know that the new chemotherapies for cancer that include an upregulation od the immune system have autoimmune diseases as a side effect. But I guess you would have to apply that harsh measures to unleash autoimmune diseases.