B cell recognition of membrane-bound antigen: an exquisite way of sensing ligands.

B cell recognition of membrane-bound antigens leads to the formation of an immunological synapse and efficient B cell activation. Ongoing research has been directed towards identifying the parameters that regulate this process. Furthermore, considerable attention has also been focused on the cell types that mediate presentation of intact antigens to B cells, as well as on the mechanisms that underlie it. Whilst there are still many unanswered questions, recent developments in these areas begin to shed light on an emerging field.