what is iga in infants
For the signals intelligence activity, see SIGAD. Selective immunoglobulin A (IgA) deficiency (SIgAD) is a genetic immunodeficiency. People with this deficiency lack immunoglobulin A (IgA), a type of antibody that protects against infections of the mucous membranes lining the mouth, airways, and digestive tract.eople with this deficiency lack immunoglobulin A (IgA), a type of antibody that protects against infections of the mucous membranes lining the mouth, airways, and digestive tract.