Artificial passive immunity usually involves administration of antiserum, and occasionally B and T cells. Antibodies are collected from donors (human or otherwise) and injected into persons who need protection immediately. Examples include ISG (immune serum globulin) and SIG (specific immune globulin).

Artificial active agents are vaccines that provoke a protective immune response in the recipient but do not cause the actual disease. Vaccination is the process of challenging the immune system with a specially-selected antigen. Examples are: 1. killed or inactivated microbes, 2. live, attenuated microbes, 3. subunits of microbes, and 4. genetically engineered microbes or microbial parts.

Vaccination programs seek to protect the individual directly through raising the antibody titer and indirectly through the development of herd immunity.

Serological tests can test for either antigens or antibodies. Most are in vitro assessments of antigen-antibody reactivity from a variety of body fluids. The basis of these tests is an antigen-antibody reaction made visible through the processes of agglutination, precipitation, immunodiffusion, complement fixation, fluorescent antibody, and immunoassay techniques.

One measurement is the titer, described as the concentration of antibody in serum. It is the highest dilution of serum that gives a visible antigen-antibody reaction. The higher the titer, the greater the level of antibody present.

Agglutination reactions occur between antibody and antigens bound to cells. This results in visible clumps caused by large antibody-antigen complexes. In viral hemagglutination testing, the antibody reacts with the antigen, and inhibits it from agglutinating red blood cells.

In precipitation reactions, soluble antigen and antibody react to form insoluble, visible precipitates. Precipitation reactions can also be visualized by adding radioactive or enzyme markers to the antigen-antibody complex.

In immunoelectrophoresis techniques such as the Western blot, proteins that have been separated by electric current are identified by labeled antibodies. HIV infections are verified with this method.

Complement fixation involves a two part procedure in which complement fixes to a specific antibody if present, or to red blood cell antigens, if antibody is absent. Lack of RBC hemolysis is indicative of a positive test.

Serological tests can measure the degree to which host antibody binds directly to disease agents or toxins. This is the principle behind tests for syphilis and rheumatic fever.

Direct fluorescent antibody tests indicate presence of an antigen and are useful in identifying infectious agents. Indirect fluorescent tests indicate the presence of a particular antibody and can diagnose infection.

Immunoassays can detect very small quantities of antigen, antibody, or other substances. Radioimmunoassay uses radioisotopes to detect trace amounts of biological substances.

The ELISA test uses enzymes and dyes to detect antigen-antibody complexes. It is widely used to detect viruses, bacteria, and antibodies in HIV infection.

Technicians use precise assays to differentiate between B and T cells, and to identify subgroups of these cells for disease diagnosis.