EVIDENCE FOR ANTIMUSCARINIC ACETYLCHOLINE RECEPTOR ANTIBODY–MEDIATED SECRETORY DYSFUNCTION IN NOD MICE (1)
In Sjogren’s syndrome (SS), autoantibodies recognize the intracellular nuclear proteins SSA/Ro and SSB/La, as well as the cell surface muscarinic cholinergic receptor (M3). Monoclonal antibodies and polyclonal antibodies against M3 were injected in NOD-scid mice and C57BL/6-scid mice to evaluate the potential roles against the loss of secretory function of exocrine tissues. The monoclonal antibodies induced loss of salivary gland function.
SS is a human autoimmune disease characterized by the loss of exocrine function of salivary and lacrimal glands. With several autoantigens, cell surface proteins have been detected as targets of autoantibodies in connective tissues. Several types of neurotransmitters or regulatory factors play a role in the control of exocrine gland secretion, such as acetylcholine and neuropeptide.
Recombinant rat M3 protein expressed by COS-7 cells was used to generate monoclonal antibodies. 28-week old male NOD.B10.H2b mice were immunized with 50 ug of urea-enriched M3 protein at 2-week intervals over 6 weeks, then used for cell fusion.
Two monoclonal IgM (2G12 and 5H9) recognize the extracellular surface domains of the receptor expressed in M3 expressing COS-7 cells.
12-14 week-old NOD-scid mice received 100 ug of anti-M3 monoclonal antibody cocktail by IP injection. The mAb cocktail reduced salivary secretion in the mice.
Similar effects were obtained in C57BL/6-scid received each monoclonal antibody. The saliva flow rates decreased 41 and 53% for 2G12 and 5H9, respectively. This result suggested NOD genetic background is not required.
This study used mice lacking the adaptive immune response (scid mutation) however, the last question is whether 2G12 and 5H9 antibodies work with C57BL/6 mice, or not.
1. K. H. Nguyen, J. Brayer, S. Cha, S. Diggs, U. Yasunari, G. Hilal, A. B. Peck, M. G. Humphreys-Beher, Evidence for antimuscarinic acetylcholine receptor antibody-mediated secretory dysfunction in nod mice. Arthritis Rheum. 43, 2297–2306 (2000).