Immunology of invertebrates: Cellular

Circulating blood cells are the primary mediators of immunity in invertebrates, carrying out the phagocytic, pathogen trapping and other inflammatory responses that protect invertebrates against infection without specific immunoglobulin antibodies and immune memory. Different immune cell types are usually specialised for different functions with, in general, immune cell diversity tending to increase with body complexity and life history. However, common to most species are phagocytic and/or granular-type cells thatsynthesise and store bioactive proteins. Cellular immunity is induced by non-self motifs on the surface of pathogens or parasites recognised by cell-derived pattern recognition receptors with diverse binding specificities. Cell death appears to be inherent in immune reactivity of many invertebrates and, in some cases, aids pathogen trapping, which prevents their spread around the body. New immune cells are produced, at least in coelomates, by mesodermal haematopoietic tissues