Detection of human T-lymphocyte receptor for sheep erythrocytes in immunoregulatory alpha-globulin.

Immunoregulatory alpha-globulin (IRA) has been shown to suppress T cell-dependent immune responses including inhibition of E-rosette formation between human peripheral lymphocytes and sheep erythrocytes. The human lymphocyte receptors, responsible for the interaction with E, can be obtained in soluble form. Recent papers have indicated that these soluble E-receptors may play a regulatory role in the thymus-dependent immune response. In the present paper a possible relationship between IRA and soluble E-receptors was investigated. Absorption of IRA with sheep erythrocytes removed its inhibitory effect upon both E-rosette formation and lymphocyte response to phytohemagglutinin. In gel diffusion experiments a pattern of total identity was obtained between a component of IRA and soluble E receptors, revealed by an anti-E-receptor-specific antiserum (obtained by immunizing a sheep with autologous erythrocytes sensitized with human soluble E-receptors). These results indicate that IRA preparations contain soluble E-receptors. The possibility that E-receptors may be related, to some extent, to the inhibitory effects of IRA protein deserves further investigation.