Cells present in this organ are morphologically very similar to vertebrate lymphocytes, and this similarity prompted the idea that the axial organ could be an ancestral lymphoïd organ. In 1966, Millott proposed that the axial organ of the sea urchin was implicated in defence mechanisms. It has also been shown that tunicates can recognize and react to alloantigenic determinants, and Hildeman et al have presented strong evidence of highly discriminating immunocompetence in echinoderms.
The works of Cooper, have first demonstrated the existence of cell-mediated immune reactions in annelids.
In Vertebrates, immunity is characterized by physiological mechanisms mediated by variuos types of cells and various soluble proteins, whose complex interplay results in a defence response which is specific and anamnesic for each particular immunogen (antigen) and which is greatly amplified in the presence of such antigen.ī-like and T-like lymphocytes, phagocytes and other cells of the reticuloendothelial system, leukines secreted by these cells, complement and humoral antibodies have been studied in great detail in vertebrates, especially in mouse and man, but little information is available on the presence(or absence) of them, especially humoral antibodies, in invertebrates.Īlthough it is largely admitted that the origin of the immune response resides among invertebrates, no definite evidence exists concerning the phylogeny of such response or the evolutionary homologies between the various components of the immune system and the components of the « immune system » of invertebrates.
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