Usual interstitial pneumonia/pulmonary fibrosis

This past year I was diagnosed with pulmonary fibrosis following a cold w/bad cough, several tests & finally surgical biopsy. I was also (seperately diagnosed) with lichen planus, and IgA and IgG tests showed several food introlances: gluten, eggs, milk, nuts. Mayo Clinic reviewed PF diagnosis and credit it to a systemic autoimmune disorder. Seems my whole immune system is involved. What could cause all this?