Abstract: The present invention relates to genetically modified B cells and their uses thereof, for example, for the treatment of a variety of diseases and disorders, including cancer, heart disease, inflammatory disease, muscle wasting disease, neurological disease, and the like. In certain embodiments, the invention relates to an isolated modified B cell (“CAR-B cell), capable of expressing a chimeric receptor (“CAR-B receptor”), wherein said chimeric receptor comprises (a) an extracellular domain; (b) a transmembrane domain; and (c) a cytoplasmic domain that comprises at least one signaling domain. In various embodiments, the invention comprises an isolated modified B cell, wherein said B cell is capable of expressing and secreting a payload, wherein the payload is not naturally expressed in a B cell or is expressed at higher levels than is naturally expressed in a B cell. In various embodiments, the payload is an antibody or fragment thereof.