IgA

**Semantic type:** Amino Acid, Peptide, or Protein|Immunologic Factor

**Definition:** IgA is the immunoglobulin subclass that is associated with antibody-mediated mucosal immunity. It is secreted as dimers into the mucosa and is the most effective isotype at fixing complement by the alternative pathway, even though it lacks the ability to fix complement by the classical pathway. There are two subtypes in the human - IgA1 and IgA2.

**Synonyms:** - Immunoglobulin A