Evolution of immunity and pathogens -- A host-pathogen interaction reduced to first principles: Antigenic variation in T. brucei -- Antigenic variation in Plasmodium falciparum -- Polymorphic mucin-like proteins in Schistosoma mansoni, a variable antigen and a key component of the compatibility between the schistosome and its snail host -- Fibrinogen-related proteins (FREP) in mollusks -- Somatic and germline diversification of a putative immunoreceptor within one phylum: Dscam in arthropods -- An immune effector system in the Protochordate gut sheds light on fundamental aspects of vertebrate immunity -- Variable lymphocyte receptors: a current view -- Antibody repertoire in fish -- Unique features of fish immune repertoires: particularities of the adaptive immunity within the largest group of vertebrates -- The evolution and structure of atypical T cell receptors -- Diversification of the primary antibody repertoire by AID-mediated gene conversion -- Antibody isotype switching in vertebrates.