The history and evolutionary pathways of defense reactions among various forms of life are reconstructed. The vertebrates evolved step-by-step from their invertebrate ancestors living in the distant past. The ancestry of vertebrate defense mechanisms must be traceable to them because these functions cannot be considered separately from the common evolutionary schema. The first part of this survey is therefore devoted to the description of major defense reactions and achievements in invertebrates. Particular emphasis is given to the taxa of present-day invertebrates most likely to exhibit some relationship to the chordates and thus to show real traces of vertebrate immune patterns. The second part involves three key assemblages of deuterostomate animals--the echinoderms, the nonvertebrate chordates, and the first vertebrates because these animals are believed to have created the prerequisites for transition from the invertebrate type of defense to the vertebrate type of adaptive immunity.

Czech Academy of Sciences Department of Immunology Prague