The cells of human body also carry antigenic determinants, but the immune cells of human body kill those cells that can recognize their own antigenic determinants during development, thus avoiding autoimmunity.
Strictly speaking, before injecting serum, an allergy test must be carried out to ensure that no immune reaction will occur.
Because poisoning must first combine with toxins, antiserum is a specific antibody produced by other animals against toxin proteins, which combines quickly.
If human beings want to be immune to serum, they need to activate a relatively long immune process and produce corresponding antibodies.
Therefore, for the injected immune serum, passive immunization takes effect before active immunization. In other words, before people are immunized with serum antibodies, these antibodies have already played a role, and the antigen-antibody complex formed has been eliminated by the human body, and it is too late to cause the immune response to it.