What type of immune complexes are formed at the zone of equivalence?

The zone of equivalence is the stage in antigen-antibody reactions where the proportions of antigen and antibody are optimal for the formation of stable immune complexes. In this zone, the concentrations of both the antigen and antibody are such that they can form complexes that can be observed and measured.

Intermediate immune complexes are formed in this zone because they consist of a balanced ratio of antigen and antibody. At this point, multiple antibodies can bind to multiple antigens, creating large complexes that are visible and can precipitate out of solution. These intermediate complexes have an ideal size that allows them to effectively engage the immune cells and elicit a robust immune response.

Small complexes are less effective in activating immune processes and might be cleared rapidly by phagocytic cells, while large complexes can be too bulky and may lead to immune complex diseases by depositing in tissues. Soluble immune complexes can also exist, but in the case of the zone of equivalence, the reference specifically points toward the stable and observable intermediate complexes that characterize this phase of the immune reaction.