The relationship between the defect in the syngeneic mixed lymphocyte reaction and thymic abnormality in New Zealand mice.

Whether a defect the syngeneic mixed lymphocyte reaction (SMLR) is caused by an abnormality in the recognition of autoantigen (Ia antigen) by T cells or by an abnormality in macrophages (Mø) which provides the Ia antigen was examined using New Zealand black (NZB) mice, a model animal for human autoimmune diseases. The level of activation of T cells by Ia antigen was lower in NZB mice than in normal mice, despite the fact that the quantity of Ia antigen expressed on the surface of Mø was much the same in the NZB mice. Furthermore, less Ia antigen was expressed on thymic reticuloepithelial cells (TRC) in NZB mice than in normal mice. These findings suggest that the defect in the SMLR in NZB mice is mainly due to T cells, namely, to abnormality in the activation of the Ia antigen receptors on the T cells, which occurs as a result of the contact between T cells and TRC in the process of T cell maturation and differentiation.