Abnormal development of the thymus in "nude" mice.

Nude mice bearing grafts of normal thymus reject skin grafts and have low, but higher than usual, lymphocyte counts. Nude bone marrow can successfully repopulate the thymus and thymus-derived areas of lethelly irradiated recipient mice. Attempts to reconstitute nude mice with normal fetal liver failed. The so-called thymic rudiment of nude mice when grafted to normal mice did not develop thymocytes. These experiments show that nude mice suffer from a defect of the epithelial portion of the thymus rather than of the precursors of thymocytes.

Role of amino groups in formation of human lymphocyte-xenogeneic erythrocyte rosettes; a proposed mechanism for antigen recognition.

Formation of coulombic and possible hydrogen bonds between amino groups on human lymphocytes and negatively charged sites on sheep erythrocytes is involved in rosette formation. Supportive evidence includes rosette inhibition by chemical binding of lymphocyte membrane amino groups, and the results of changing the pH, ionic concentration, and temperature of the reaction. Although the possibility has not been excluded that the amino group dependence of this reaction is related to the property of certain proteins attached to the T-cell (thymus processed) surface, it is suggested that this dependence may be related to a charge pattern recognition in the form of "codes" present on the T-cell membrane. It is speculated that this type of recognition may be a contributory mechanism in the initiation of the T-cell-dependent immune response.