title: The evolution of the cell--cell recognition system.
mesh_terms: D000818:Animals; D005075:Biological Evolution; D002449:Cell Aggregation; D002450:Cell Communication; D005796:Genes; D008040:Genetic Linkage; D008285:Major Histocompatibility Complex; D008565:Membrane Proteins / Q000502:physiology; D012723:Sex
chemical_list: D008565:Membrane Proteins