Antibodies to nucleic acid haptens can be made in the laboratory, but they are rarely made in vivo. Antibodies to DNA or RNA do occur in patients with systemic lupus erythematosus, Crohn's disease, or amyotrophic lateral sclerosis. Adjuvants have been derived from vaccinia virus and other poxviruses, BCG, and Salmonella , each transfected with genes for an antigen of interest. Others have come from lipopolysaccharide derivatives, such as monophosphoryl lipid A. Freund's complete adjuvant, which consists of dead mycobacteria in oil emulsified with an antigen in aqueous solution, is now used infrequently because it generally causes a strong local inflammatory reaction. The aluminum salt alum is approved for general use as an adjuvant in humans.
Liposomes can also act as adjuvants.
Membrane proteins, such as viral coat proteins, inserted in liposomes are more antigenic than those solubilized in detergents. In some cases, liposomes have been found to enhance the immune response to small antigens, which suggests that liposomes can be used in vaccines. Clinically, adjuvants are used as adjuncts in certain immunizations, such as tetanus, and are potentially important in antiparasitic and antitumor therapy. The response to antigen exposure is dependent on both the route of administration and the dose. In general, antigens entering the body by intravenous routes travel rapidly to the spleen, and antibody is quickly produced.