Sociability as a personality trait in animals: methods, causes and consequences.

Within animal populations there is variation among individuals in their tendency to be social, where more sociable individuals associate more with other individuals. Consistent inter-individual variation in 'sociability' is considered one of the major axes of personality variation in animals along with aggressiveness, activity, exploration and boldness. Not only is variation in sociability important in terms of animal personalities, but it holds particular significance for, and can be informed by, two other topics of major interest: social networks and collective behaviour.

Antibody responses of variable lymphocyte receptors in the lamprey.

Lamprey and hagfish, the living representatives of jawless vertebrates, use genomic leucine-rich-repeat cassettes for the combinatorial assembly of diverse antigen receptor genes encoding variable lymphocyte receptors of two types: VLRA and VLRB. We describe here the VLRB-bearing lineage of lymphocytes in sea lamprey. These cells responded to repetitive carbohydrate or protein determinants on bacteria or mammalian cells with lymphoblastoid transformation, proliferation and differentiation into plasmacytes that secreted multimeric antigen-specific VLRB antibodies.

Expression of the immunoregulatory molecule FcRH4 defines a distinctive tissue-based population of memory B cells.

The FcRH4 transmembrane molecule, a member of the Fc receptor homologue family, can potently inhibit B cell receptor (BCR) signaling. We show that cell surface expression of this immunoregulatory molecule is restricted to a subpopulation of memory B cells, most of which lack the classical CD27 marker for memory B cells in humans. The FcRH4+ and FcRH4- memory B cells have undergone comparable levels of immunoglobulin isotype switching and somatic hypermutation, while neither subpopulation expresses the transcription factors involved in plasma cell differentiation.

FcRH1: an activation coreceptor on human B cells.

B-cell activation and differentiation is regulated through the coordinated function of a dynamic array of cell surface receptors. At different stages in their differentiation, human B cells may express one or more members of a large family of immunoglobulin Fc receptor homologs (FcRH) with regulatory potential. Among these newly identified transmembrane molecules, FcRH1 is unique in having 2 immunoreceptor tyrosine-based activation motif (ITAM)-like motifs in its intracellular domain.