If some vaccine component is similar to a protein produced by the body itself, then once the immune system learns how to react to the vaccine protein, it may also learn to react to its own protein (the one similar to the vaccine protein) in the same way. This is how one gets autoimmune disease. This phenomenon is called molecular mimicry.
This article explains the mechanism of molecular mimicry between tetanus toxoid and IgE receptor, which is probably what leads to an increased risk of allergies in vaccinated people.
Hyper-immunization of mice against tetanus causes antiphospholipid syndrom. This is also a result of molecular mimicry.
It seems that in humans, tetanus, hepatitis B and influenza vaccines also cause this disease., 
It is reported here that the tetanus vaccine can lead to autoimmune diseases.