Secretory IgA

Causes of elevated fecal sIgA:

- Any defective epithelial barrier

- A defective epithelial barrier allows bacterial and microbial penetration, which is the strongest stimulator of sIgA production.

- Celiac disease

- Colon cancer

- Infections

- IBS (especially the diarrhea subtype)

Therapeutic considerations for elevated fecal sIgA:

Assess for and treat root causes of immune upregulation /inflammation:

- Infection (bacterial, parasitic, and/or viral pathogen, potential pathogen)

- Compromised intestinal barrier function (i.e., intestinal permeability)

- Heightened response to noninfectious stimuli (i.e., food sensitivity/allergy, etc.)

Consider Food Antibody testing – If positive, consider elimination diet

Considerations for low fecal sIgA:

Because of the lack of clinical evidence, there is no clear cut-off value for low fecal sIgA. People with systemic IgA deficiency can have low levels of fecal secretory IgA. There is a demonstrated link between IgA deficiency and several GI diseases, including:

- celiac disease,

- giardiasis,

- nodular lymphoid hyperplasia,

- ulcerative colitis,

- Crohn’s disease,

- pernicious anemia,

- and gastric and colonic adenocarcinoma.

Low sIgA may reflect a loss of GI immune response resiliency. Fecal sIgA may be low in severe/prolonged IBD patients due to a switch from intestinal IgA to IgG production as well as a deficiency in producing IgA dimers and polymers.

Secretory IgA demonstrates an array of activities integral to the maintenance of intestinal homeostasis. It influences the composition of intestinal microbiota, down-regulates pro-inflammatory responses normally associated with the uptake of highly pathogenic bacteria and potentially allergenic antigens, and promotes the retro-transport of antigens across the intestinal epithelium to gut-associated lymphoid tissue (GALT). Therefore, a low sIgA is clinically significant.

The test result should be considered together with any other medical condition, other biomarkers, and microbiome profiles when interpreting the data.

As the most abundant class of antibody found in the human intestinal lumen, secretory IgA (sIgA) is recognized as a first line of defense in protecting the intestinal epithelium from enteric pathogens and toxins. It is used to assess gastrointestinal barrier function.