Cross-reactions
Cross-reactions play an important role in the PHM hypothesis. Trost et
al[21] found that “no human protein is exempt from bacterial
motifs.” This extensive cross-reactivity may be quite significant. It
might be that plant microbiomes have a similar level of cross-reactivity
with plant proteins. This might mean that food hypersensitivity of
multiple types might be at least partly due to microbial antigens found
in plants cross-reacting with food allergens. Plant microbes that
increase after harvest and thus reach elevated levels in stored food
(both from plants and potentially the animals that consume them) might
be a source of cross-reacting PHM. These cross-reactions could magnify
the effect of low-level microbial colonization.
The level of colonization by a PHM could explain why one person reacts
to a particular substance and another does not. The location that the
microbe has colonized could potentially determine the type and location
of the reaction. For instance, colonization of the skin might lead to
atopic dermatitis, colonization of the intestines might lead to
diarrhea, and colonization of blood vessels might lead to cardiovascular
signs and symptoms.
Cross-reactions might be a significant part of the processes that lead
to chronic inflammatory disease, as suggested by two recent examples.
Bacher et al[22] provided evidence that a cross-reaction between
intestinal C. albicans and lung Aspergillus fumigatus could, under
certain circumstances, lead to the inflammatory lung disease, allergic
bronchopulmonary aspergillosis. These two fungal species could be
considered to be PHM. High A. fumigatus exposures can occur with certain
farming exposures or due to water-damaged buildings. C. albicans
overgrowth might arise from a westernized diet and antibiotics, as
mentioned above.
The second example is a recent study[23] that found that Pseudomonas
fluorescens, an environmental bacteria, cross-reacts with gliadin and
might possibly be linked to celiac disease. P. fluorescens is
cold-tolerant and can survive in refrigerated food, and is found in
moldy buildings and on walls and shower fixtures[24]. Thus, it is
potentially a PHM.