Immune complexes are combinations of antigen and antibody that are capable of activating the complement cascade. Although the activated agent is directed against the immune complex, tissues that are "innocent bystanders" may also be severely damaged, especially when immune complexes are produced too rapidly for adequate clearance by the body. Immune complexes are commonly present in autoimmune disorders and also are found in immune hypersensitivities that do not involve autoimmunity.

Two methods can be used to determine the circulating immune complexes (CIC) in the blood in the diagnosis of autoimmune and infectious diseases. One involves screening for large amounts of precipitate in serum that has been refrigerated. The other is the Raji cell assay, in which these specially prepared cells that bind complement (C3) are combined with the serum sample and then incubated. Further incubation with a radiolabeled antihuman immunoglobulin allows for binding of the CIC on the surface of the Raji cells. This is followed by washing of the cells and measurement of the radioactivity to determine the CIC in the blood.²⁵

• Immune complexes are not normally found in the serum.

• Rough handling of the sample and failure to transport the sample promptly to the laboratory may cause deterioration of any immune complexes present.

• Suspected immune disorders such as SLE, scleroderma, dermatomyositis, polymyositis, glomerulonephritis, and rheumatic fever as indicated by the presence of immune complexes
• Monitoring of the effects of therapy for various immune disorders
• Suspected serum sickness or allergic reactions to drugs as indicated by the presence of immune complexes

Nursing Care Before the Procedure

Client preparation is the same as that for any study involving the collection of a peripheral blood sample (see Appendix I).

A venipuncture is performed and the sample collected in a red-topped tube or other type of blood collection tube, depending on laboratory preference. The sample must be handled gently and transported to the laboratory promptly.

Nursing Care After the Procedure

Care and assessment after the procedure are the same as for any study involving the collection of a peripheral blood sample.

• Complications and precautions: Note and report the presence of complexes in relation to signs and symptoms of an existing or suspected autoimmune disease.