IgA

Immunoglobulin A (IgA) is a type of antibody in the immune system, which is produced by mucosa associated lymphoid tissues. IgA mainly exists in secretions of tissues such as digestive tract, bronchus, mammary gland, and lacrimal gland, constituting the mucosal immune defense. In clinical practice, IgA can assist in the diagnosis of lymphoma. For example, its positive expression is an important pathological feature of primary malignant lymphoma of thyroid. In addition, some epithelial tumors such as nasopharyngeal cancer, gastric cancer, colorectal cancer, breast cancer, ovarian cancer, and cervical cancer may undergo gene rearrangement and abnormally secrete IgA, and the patients have worse prognosis, speculated that the tumor derived IgA can accelerate cell cycle to promote proliferation, and interfere with immune response to mediate immune escape. Meanwhile, IgA+ B cells in tumors can inhibit cytotoxic T cell (CTL) production, and IgA+ plasma cells can induce CTL depletion. In addition, IgA deposition in glomerulus will cause inflammatory cell aggregation and complement system activation, which may be the key factor in the pathogenesis of IgA nephropathy.