antiserum

An antiserum is a serum that contains antibodies against a specific antigen. It is produced by immunizing a donor animal or human with the target antigen to raise a high-titer antibody response, after which the serum is collected and processed for therapeutic use. Antiserum provides passive immunity, delivering ready-made antibodies that can act immediately but offer only temporary protection as the antibodies are eventually cleared from the circulation.

Common applications include treatment or prevention after exposure to pathogens or toxins. Historically important uses include antitoxins and antisera for diphtheria, tetanus, and rabies, as well as antivenoms for snake bites and other envenomations. In many cases, the antiserum is polyclonal, containing a mixture of antibodies that recognize multiple epitopes on the target antigen. Modern medicine increasingly relies on human-derived immunoglobulin preparations and monoclonal antibodies, which can provide more consistent safety and specificity.

Safety considerations are central to antisera. Because the antibodies may originate from non-human sources, reactions such as serum sickness or anaphylaxis can occur. To reduce risk, antisera are screened and treated to inactivate pathogens, and newer products aim to minimize non-antibody components. There is also ongoing use of intravenous immunoglobulin and monoclonal antibodies for various indications, reflecting a shift from traditional antisera toward more targeted therapies.

Antiserum is distinct from antisera-derived products; antitoxin is a term for antibodies that neutralize toxins and is a subset of antiserum.