What do immune complexes precipitate in tissues, leading to inflammation?

Immune complexes consist of antigens bound to antibodies. When these immune complexes accumulate in tissues, they can activate the complementary cascade, which is a critical part of the immune system's response. The complement system consists of a series of proteins that, when activated, can lead to a variety of immune responses, including inflammation.

When immune complexes are deposited in tissues, they facilitate the recruitment and activation of complement proteins, leading to increased vascular permeability, chemotaxis of inflammatory cells, and ultimately tissue damage. This process contributes to the inflammation seen in various autoimmune and inflammatory diseases, such as systemic lupus erythematosus or rheumatoid arthritis. The role of complement proteins in mediating inflammation through immune complex deposition is well-established in immunopathology.

Other options like neutrophils, T-cells, and autoantibodies play important roles in the immune response, but they do not directly precipitate inflammation through the deposition and activation of immune complexes in the same manner as complement proteins do. Neutrophils are recruited to sites of inflammation, T-cells are involved in adaptive immune responses, and autoantibodies may contribute to pathology, but it is the complement system that is directly activated by the immune complexes to trigger the inflammatory response in the tissues