F1 hybrid offspring of New Zealand Black mothers and New Zealand White fathers [(NZB X NZW)F1] female mice develop antibodies to single-stranded (ss) and native DNA, immune complex glomerulonephritis, massive proteinuria, and premature death with renal failure. By a series of matings, congenic (NZB X NZW)F1 . xid/xid mice were prepared. These mice were different from (NZB X NZW)F1 mice in having the X chromosome-linked immune deficiency gene, xid, in homozygous form. Such congenic (NZB X NZW)F1 . xid/xid females failed to develop antibodies to single-stranded or native DNA. They also failed to develop fatal renal disease as measured by proteinuria, glomerular histology, glomerular immunofluorescence, and survival. To control for unknown genetic factors, studies were performed with littermates that were derived by mating NZB . xid/+ females with NZW . xid/Y males such that the resulting offspring were either (NZB X NZW)F1 . xid/xid (and therefore "defective") or (NZB X NZW)F1 . xid/+ [phenotypically like (NZB X NZW)F1]. In these and in additional studies, mice were housed in the same cages and identified by ear tagging so as to avoid possible environmental variations from cage to cage. In these studies, xid/xid mice failed to develop the characteristic signs of autoimmunity, whereas the controls did. Similar results were also obtained with (NZW X NZB)F1 xid/xid mice compared with (NZW X NZB)F1 xid/+ mice. The effect of xid/xid upon (NZB X NZW)F1 mice was further investigated by assessing responses to immunization and polyclonal B cell activation in vivo. The xid/xid mice failed to produce anti-ssDNA following immunization with ssDNA complexed to a protein carrier in fluid form or even emulsified in adjuvant. Finally, the xid/xid mice failed to produce antiDNA in response to multiple injections of the polyclonal activator, bacterial lipopolysaccharide (LPS), or the polyclonal activator, polyribose inosinic acid . polyribose cytidylic acid. However, the xid/xid mice were neither generally hyporesponsive nor unable to recognize LPS because they made normal antibody responses following immunization with LPS to which multiple trinitrophenyl groups were chemically attached. We conclude from these studies that xid/xid, which is known to cause the deletion of a B cell subset, has a profound affect upon (NZB X NZW)F1 mice, rendering them insusceptible to the naturally occurring autoimmune disease characteristic of (NZB X NZW)F1 mice, and preventing them from producing antibodies to DNA despite purposeful immunization and polyclonal B cell activation. These results force a reevaluation of previous concepts regarding the mechanisms by which xid/xid might interfere with the development of autoimmunity, and a consideration of therapeutic implications.
B J Steinberg, P A Smathers, K Frederiksen, A D Steinberg