Y. Zhang et al., A pivotal role of cell-bound but not soluble CD4 molecules in full development of lupus-like manifestations in MRL-Fas(lprcg)/Fas(lprcg) mice, CLIN EXP IM, 122(1), 2000, pp. 124-132
The role of CD4 molecules in the autoimmune and lymphoproliferative syndrom
e caused by murine Fas mutations was studied using the novel systemic lupus
erythematosus (SLE) model, MRL-Fas(lprcg)/ Fas(lprcg) (MRL-lpr(cg)) mice,
in combination with the novel mutant CD4 gene producing soluble CD4 (sCD4)
instead of membrane-bound CD4 (mCD4). For this purpose, various autoimmune
manifestations were compared among MRL-lpr(cg) mice homozygous (CD4(s)-lpr(
cg)), heterozygous (CD4(s/m)-lpr(cg)), and wild-type (CD4(m)-lpr(cg)) for t
he CD4 mutation. The mortality, glomerulonephritis, proteinuria, and lympha
denopathy were significantly ameliorated in CD4(s)-lpr(cg) compared with CD
4(m)-lpr(cg) and CD4(s/m)- lpr(cg) mice, both being comparable in these cli
nical characteristics. In parallel with the clinical improvement, the serum
levels of immunoglobulin, anti-DNA antibodies, anti-nuclear antibodies and
immune complexes, and the extent of glomerular immune deposition, were sig
nificantly lower in the former. The results indicate that mCD4 is important
and can not he replaced by sCD4 in full development of SLE-like manifestat
ions, and suggest that CD4(+) T cells may aggravate the autoimmune disease
by stimulating autoreactive B cells to produce autoantibodies through their
helper activity in Fas mutant models. The sCD4 levels in the serum and spl
een elevated with the increased accumulation of B210(+)CD4(-)CD8(-) (double
-negative (DN)) T cells in CD4(s)-lpr(cg) mice. This, together with the sig
nificantly milder lymphadenopathy associated with lower DN T cell contents
in CDC-lpr''* than CD4(m)-lpr(cg) mice, implies that some of abnormal DN T
cells may be derived from cells of the CD4 lineage.