What is the visible serological reaction between soluble antigen and its specific antibody called?

The visible serological reaction between soluble antigen and its specific antibody is known as precipitation. This phenomenon occurs when soluble antigens and their corresponding antibodies form larger complexes that can become insoluble and precipitate out of solution.

In precipitation reactions, the interaction between antigens and antibodies can be visualized through a turbid or cloudy solution due to the formation of these immune complexes. This reaction is particularly useful in laboratory settings to identify the presence of specific antigens or antibodies in a sample. The formation of a precipitate typically indicates that the antigen and antibody are present in optimal ratios, leading to efficient cross-linking and aggregation.

The other options represent different immunological reactions that do not pertain to soluble antigens and antibodies forming visible precipitates. Neutralization refers to the process whereby antibodies block the biological activity of an antigen, typically a virus or toxin. Hemagglutination involves the clumping of red blood cells due to the presence of agglutinating antibodies or antigens, while inhibition generally refers to a decrease in a particular immune response or activity, rather than the formation of visible immune complexes. In this context, precipitation is the most direct answer to the question regarding the visible serological reaction.