VLRBexpressing

VLRB-expressing refers to cells that express the variable lymphocyte receptor B (VLRB) in jawless vertebrates, notably lampreys. VLRBs are leucine-rich repeat glycoproteins that function as antigen receptors on the surface of B-like lymphocytes and can also be secreted as soluble antibodies. In lampreys, the adaptive-like immune system comprises three lymphocyte lineages—VLRA, VLRB, and VLRC—with VLRB-expressing cells acting analogously to B cells in jawed vertebrates.

Receptor assembly in VLRB-expressing cells occurs through somatic rearrangement of donor leucine-rich repeat modules, generating immense receptor diversity without immunoglobulin gene rearrangement. This somatic diversification allows VLRB-expressing lymphocytes to recognize a wide range of protein and non-protein antigens. Following antigen exposure, VLRB-expressing cells can proliferate and differentiate, producing cell-surface VLRB receptors and, in many cases, secreted multimeric VLRB molecules that participate in antigen binding and neutralization.

Detection and study of VLRB-expressing cells use molecular and immunological tools such as RT-PCR for VLRB transcripts, in situ hybridization, and immunostaining with anti-VLRB reagents. Functional assessment often includes measuring antigen-specific responses, proliferation, and antigen binding by the secreted or surface-displayed VLRB.

The study of VLRB-expressing cells provides insight into the evolution of adaptive immunity, illustrating an alternative receptor architecture and strategy for antigen recognition in vertebrates. VLRB-expressing lymphocytes exemplify the distinct but functionally parallel approach to immune defense observed in jawless vertebrates.