Immune complexes formed as a result of immunologic reactions and increased serum immunoglobulins, such as immunoglobulin A (IgA), circulate in the bloodstream and are deposited on the glomerular membranes. Components of the immune system, including complement, neutrophils, lymphocytes, monocytes, and cytokines, are then attracted to the area, producing changes and damage to the membranes. Depending on the immune system mediators involved, damage may consist of cellular infiltration or proliferation resulting in thickening of the glomerular basement membrane, and complement-mediated damage to the capillaries and basement membrane.