Mitogenic lectins bind to the antigen receptor on human lymphocytes

Area of Science:

• Immunology
• Cell Biology
• Biochemistry

Background:

• Cell surface receptors on human lymphocytes play crucial roles in immune responses.
• Lectins are proteins that bind carbohydrates, offering a tool to probe cell surface molecules.
• Disulfide-linked heterodimers are important components of lymphocyte surface receptors.

Purpose of the Study:

• To investigate the binding specificity of mitogenic and non-mitogenic lectins to disulfide-linked cell surface receptors on human lymphocytes.
• To identify and characterize lectin-binding polypeptides on lymphocyte surfaces.
• To explore the interaction of lectins with T cell receptors (TcR) and CD3.

Main Methods:

• Surface radioiodination of human tonsil lymphocytes and T lymphoblastoid cells.
• Absorption of cell lysates with lectin-agarose derivatives and immunoprecipitation with monoclonal antibodies.
• Two-dimensional gel electrophoresis (nonreduced/reduced) of lectin eluates and immunoprecipitates.
• Analysis of radiolabeled polypeptides by autoradiography.

Main Results:

• Pea lectin, concanavalin A, and lentil lectin bound two disulfide-linked heterodimers (II and III) and two homodimers (I and IV) on tonsil lymphocytes.
• Leukoagglutinating (L)- and erythroagglutinating (E)-phytohemagglutinins (PHA) bound heterodimers II, III, and homodimer IV.
• Pokeweed mitogen recognized only heterodimers II and III.
• Heterodimer II likely represents TcR alpha/beta, and heterodimer III may represent TcR gamma.
• Evidence suggests E-PHA interacts with both TcR and CD3.

Conclusions:

• Mitogenic lectins interact with specific disulfide-linked molecules on human lymphocytes, including TcR alpha/beta and potentially TcR gamma.
• Non-mitogenic lectins also recognize these receptors, albeit with lower affinity.
• These findings contribute to understanding lectin-lymphocyte interactions and characterizing cell surface receptors.