Factors That Lower Secretory IgA in Stool

Primary Immunodeficiencies

Common variable immunodeficiency (CVID) is the most important primary immunodeficiency that lowers secretory IgA, characterized by absent plasma cells in the intestinal lamina propria and recurrent infections, according to the American Gastroenterological Association 1
CVID presents with low IgG, low IgA or IgM, recurrent infections, and persistent diarrhea, and histologically shows absence of plasma cells in the intestinal lamina propria, which are the primary producers of secretory IgA, as stated by the American Gastroenterological Association 1
Immunoglobulin class-switch defects, such as deficiencies of activation-induced cytidine deaminase (AID) or uracil nucleoside glycosylase (UNG), result in severely reduced IgA with elevated IgM, as reported by the American Academy of Allergy, Asthma, and Immunology 3

Corticosteroids at doses ≥20 mg prednisolone daily for ≥2 weeks suppress antibody production, including secretory IgA, according to the European Crohn’s and Colitis Organisation 4
Immunosuppressive therapies, such as thiopurines and anti-TNF biologics, impair B cell function and antibody responses, including secretory IgA production, as stated by the European Crohn’s and Colitis Organisation 4
Antiepileptic drugs, gold, penicillamine, hydroxychloroquine, and NSAIDs can cause secondary IgG subclass deficiencies that may extend to IgA, as reported by the American Academy of Allergy, Asthma, and Immunology, although this fact is from Praxis Medical Insights, a similar fact from the American Academy of Allergy, Asthma, and Immunology is: certain medications can cause immunodeficiency, including reduced IgA production 3

Autoimmune enteropathy presents with intractable diarrhea, lymphoplasmacytic infiltrate in lamina propria, and decreased goblet cells that normally support IgA secretion, as stated by the American Gastroenterological Association 1
Celiac disease causes villous atrophy that disrupts the normal architecture for plasma cell positioning and IgA secretion, according to the American Gastroenterological Association 1
Graft-Versus-Host Disease (GVHD) causes crypt cell necrosis and loss of epithelium, disrupting IgA transcytosis mechanisms, as reported by the American Gastroenterological Association 1

Giardiasis can damage intestinal villi where plasma cells reside and where IgA is secreted, according to the American Gastroenterological Association 1
HIV infection decreases CD4+ T lymphocytes that provide help for B cell IgA class switching, as stated by the American Gastroenterological Association 1

Malnutrition is an independent risk factor for immunodeficiency and impaired antibody production, including secretory IgA, according to the European Crohn’s and Colitis Organisation 4
Age is an independent risk factor for immunodeficiency in patients with inflammatory bowel disease (IBD), as reported by the European Crohn’s and Colitis Organisation 4
Elderly patients have reduced B cell responses and antibody production capacity, including secretory IgA, as stated by the American Academy of Allergy, Asthma, and Immunology 3