Serum is the clear fluid portion of blood. It does not contain blood cells but does contain many proteins , including antibodies , which are formed as part of the immune response to protect against infection. Antiserum is a preparation of serum that has been removed from a person or animal that has already developed immunity to a particular microorganism. It contains antibodies against that microorganism. Examples include antiserum for tetanus and rabies exposure.
Serum sickness is a hypersensitivity reaction similar to allergy .
The immune complexes are deposited in various tissues, causing inflammation and various other symptoms. Because it takes time for the body to produce antibodies to a new antigen, symptoms do not develop until 7 to 14 days after exposure to the antiserum. The drug molecules probably combine with a protein in the blood before being misidentified as an antigen. Serum sickness is different from anaphylactic shock , which is an immediate reaction with more severe symptoms. There is no known way to prevent the development of serum sickness.