Soluble immune complexes are formed under what condition?

Soluble immune complexes are formed when there is an antigen excess, which is the correct choice in this scenario. This occurs when there is a higher concentration of antigens compared to the available antibodies. In such situations, the antibodies bind to the excess antigens, resulting in the formation of large, soluble complexes. These complexes can circulate in the bloodstream without precipitating out and are critical in various immune responses.

When antigens are present in large amounts, the likelihood of forming these soluble immune complexes increases, as there are more antigen particles available to bind to the antibodies. This phenomenon is important in understanding various immunological diseases and the dynamics of immune responses, particularly in conditions where antigen levels might be abnormally high, such as in certain infections or autoimmune diseases.

The condition of antigen deficit would lead to a lack of complex formation, and antibody deficit would mean there aren't enough antibodies to form complexes regardless of antigen levels. The equivalence condition describes the optimal balance between antigens and antibodies where complex formation occurs but typically results in precipitates rather than soluble complexes. Therefore, the formation of soluble immune complexes is primarily associated with the presence of an excess of antigens in relation to antibodies.