Researchers show that immunoglobulin A fine-tunes the body's interactions with microbes

Immunoglobulin A (IgA) deficiency is the most common primary immune deficiency worldwide, but its presentation has puzzled physicians and researchers. Some with the disorder present with symptoms like recurrent infections, autoimmune disease, or allergies, whereas others have no symptoms at all and only become aware of their IgA-deficient status through an incidental finding on a blood test. This variability has raised the question among researchers: Why aren't many of those with IgA deficiency sicker?