Principles of paramunization. Option and limits in veterinary medicine.

The so-called primitive immune system has not changed during evolution. Even in primates it plays the most important role in first line defence against invading microorganisms. Cellular components such as macrophages, granulocytes, Natural Killer cells and gamma delta-T cells and soluble humoral factors--the cytokines--are the representatives of the primitive immune system. An interlocking communicative network regulates flexible response of effector cells towards "non-self" antigens. It also ensures close connection with the repertoire of specific immune response, e.g. antibody formation. Multifactorial diseases, nosocomial infections, tumour diseases and various forms of immuno-suppression initiated alternative methods in immunotherapy. Immunostimulation at the non-specific defense level has first been noticed as "side effects" of vaccination. Today it should be differentiated between substitution of the immune system with cytokines and induction of the non-specific defense repertoire mimicking natural antigen contact that is called paramunization. Advantages and disadvantages of both methods are discussed. In vitro as well as in vivo experiments with poxviruses document safety and efficacy of purified and inactivated virus particles in paramunization protocols. The main stimulative components of the poxvirus particles are located in the envelope of the virions. Poxvirus-induced stimulation of non-specific defense reactions is likely to have remote effects on the quality of further antigen processing. Besides the induction of a high short-term alertness in the primitive immune system paramunization may efficiently influence ongoing specific responses, e.g. immunoglobulin isotype selection. Therefore the term paramunization should not be used to characterize a separate part of the immune system, however, for didactic reasons it will facilitate the understanding of principles of the immune system.