Do foods contain immunoglobulins?

Probably not... Immunoglobulins (antibodies) are proteins used by the immune system to identify and eliminate unknown cells (like germs). They are found in body fluids like blood, tears, saliva, & breast milk. If foods are consumed raw or barely cooked, there is a chance that you are also consuming immunoglobulins from that animal. In most cases, the cooking or pasteurization process destroys these proteins.
No. The food itself is an antigen that stimulates our own immune system to make antibodies. Most people do not have issues with this, some do have allergic reactions due to the antigen-antibody problem.