Which hypersensitivity reaction involves immune complex deposition?

The correct response is that Type III hypersensitivity reactions involve immune complex deposition. This type of hypersensitivity occurs when antibodies bind to soluble antigens, forming immune complexes. These immune complexes can deposit in various tissues, leading to an inflammatory response that can cause damage to those tissues.

In contrast to Type I hypersensitivity, which is mediated by IgE and involves immediate reactions often related to allergens, Type II hypersensitivity is characterized by the direct antibody-mediated destruction of cells. Meanwhile, Type IV hypersensitivity is delayed and primarily mediated by T cells rather than antibodies. This distinction is important in understanding the different mechanisms and consequences of each type of hypersensitivity reaction. Type III's mechanism is well noted for its role in conditions such as systemic lupus erythematosus and rheumatoid arthritis, where immune complexes play a pivotal role in disease pathology.