Receptors for IgA on human thymus cells in myasthenia gravis.

Specific surface receptors for the Fc region of human immunoglobulin A (FcαR) were identified on the thymus cells of all 15 patients affected by myasthenia gravis. A large variation of the percentage of FCαR bearing thymus cells was recorded (9.5 66.0% mean value 279± 17.8) the high values being associated in most cases with the thymus hyperplasia and the low values with a lipomatosis of the organ. Even the lowest percentage of FcαR bearing cells recorded in myasthenia gravis are considerably higher than those found in normal subjects (0.4-4.1; mean value 1.8) demonstrating that the expression of FcαR on the thymus cells is the consequence of the disease. No attempts were made to identify the cell population bearing FCαR bus indirect results indicate that the cells belong to E-rosette forming population. and, in some cases, to a null cell population devoid of the ability to form E and EAC rosettes. EcαR can hind various IgA ligands and the binding is confined to a small fraction of IgA (not more than 5%) considered as cytophilic IgA. [ABSTRACT FROM AUTHOR]