Deficiency in beta(2)-microglobulin, but not CD1, accelerates spontaneous lupus skin disease while inhibiting nephritis in MRL-Fas(lpr) mice: An example of disease regulation at the organ level

When mutations that inactivate molecules that function in the immune system have been crossed to murine lupus strains, the result has generally been a uniform up-regulation or down-regulation of autoimmune disease in the end organs. In the current work we report an interesting dissociation of target organ disease in beta (2)-microglobulin (beta (2)m)-deficient MRL-Fas(lpr) (MRL/lpr) mice: lupus; skin lesions are accelerated, whereas nephritis is ameliorated. beta (2)m deficiency affects the expression of classical and n onclassical MHC molecules and thus prevents the normal development of CD8- as well as CD1-dependent NK1(+) T cells. To further define the mechanism by which beta (2)m deficiency accelerates skin disease, we studied CD1-defici ent MRL/lpr mice. These mice do not have accelerated skin disease, excludin g a CD1 or NK1(+) T cell-dependent mechanism of beta (2)m deficiency. The d ata indicate that the regulation of systemic disease is not solely governed by regulation of initial activation of autoreactive lymphocytes in seconda ry lymphoid tissue, as this is equally relevant to renal and skin diseases. Rather, regulation of autoimmunity can also occur at the target organ leve l, explaining the divergence of disease in skin and kidney in beta (2)m-def icient mice.