Cross-reactions

Cross-reactions play an important role in the PHM hypothesis. Trost et al[100] found that “no human protein is exempt from bacterial motifs.” The extensive cross-reactivity they found between only 40 bacterial species and human self-tissue is significant. It also may have implications for agricultural products. It seems plausible that the plant-associated microbiota would have a similar high level of cross-reactivity with plant proteins. The PHM hypothesis proposes that food hypersensitivity might be at least partly related to plant-associated microbial antigens cross-reacting with known food allergens.
Plant microbes that increase after harvest and reach elevated levels in stored food might be a source of PHMs that colonize humans. PHMs would also likely be present in animal products, due to the animals’ microbiotas including PHMs they acquired from their food and other sources. Cooking eliminates most of the microbes but is likely insufficient to eliminate all PHMs.
Cross-reactions are a potentially significant factor in CIDs as suggested by two recent examples. Bacher et al[101] provided evidence that a cross-reaction between two fungi, intestinal C. albicans and lung A. fumigatus, could lead to the inflammatory lung disease, allergic bronchopulmonary aspergillosis. Both fungi might be considered to be PHMs. High A. fumigatus exposures can occur in farming[102] or in damp or water-damaged buildings[103,104]. C. albicans overgrowth might be related to westernization-associated factors, such as diet[105] and medication[106].
Another example is a study[107] that found that Pseudomonas fluorescens cross-reacts with gliadin and might be linked to celiac disease. P. fluorescens can survive in refrigerated food and is found in moldy buildings, on walls and shower fixtures[108] and thus might be a PHM.