Figure 5.

Inhibition of‘[³H]QNB binding to NOD parotid gland membranes by primary Sjögren’s syndrome IgG (n = 5; open circles) or normal patient IgG (n = 3; solid circles). Increasing concentrations of human IgG were incubated with parotid gland membranes followed by the addition of 0.5 nM radiolabeled ligand agonist (21) (solid lines). Immunoprecipitation of [³H]QNB-labeled muscarinic receptors by normal and patient IgG is represented by the dashed lines. The results are the mean ± SE for Sjögren’s syndrome patients (#36, 71, 77, 93, 97) and normal healthy controls (#4, 5, 6) performed on two separate occasions in duplicate. Control binding of 100% refers to the value of [³H]QNB bound to the membrane without the addition of antibody reagents (20).