Immune response in the sea urchin Lytechinus pictus.
The sea urchin shows an immune response to grafted tissue similar to that found in vertebrates. Unrelated animals rejected allografts in about 30 days. Acceptance of allografts was observed for tissue exchanged between some F2 and F3 inbred animals. The percentage  of acceptances reflected the degree of inbreeding. Accelerated second set rejection was also found. These grafts were rejected in one-third of the time compared to first sets.
D000818:Animals; D005796:Genes; D006084:Graft Rejection; D007156:Immunologic Memory; D010802:Phylogeny; D012617:Sea Urchins / Q000276:immunology*; D016038:Skin Transplantation; D013997:Time Factors; D014182:Transplantation, Autologous; D014184:Transplantation, Homologous