CD28 knockout mice as a useful clue to examine the pathogenesis of chronic graft-versus-host reaction

Injection of BALB/c or DBA/2 spleen cells into F1 C57BL/6 (B6) hybrids induces a graft-versus-host reaction (GVHR) of a chronic stimulatory type that results in clinical and pathologic manifestations that resemble the human systemic lupus erythematosus (SLE). The aim of the present study was to examine the role of a major T-cell costimulatory signal receptor, CD28, in the production of autoantibody and the development of an immune complex glomerulonephritis, which are common in SLE pathology.

For this purpose, CD28-deficient (CD28KO) mice were used for the source of donor lymphocytes. Chronic GVHR was induced by an injection of BALB/c or BALB. CD28KO donor cells into normal BCF1 mice. Serum titers of anti-dsDNA antibodies were assessed by enzyme-linked immunosorbent assay (ELISA) and major histocompatibility complex (MHC) class II antigen expression on B cells were tested by flow cytometry. In addition, depositions of immunoglobulin (Ig) were examined by direct immunofluorescence staining on frozen kidney sections.

When (BALB/c x B6)F1 mice were injected with parental BALB/c lymphocytes, serum anti-dsDNA titer was significantly increased in association with nonspecific B-cell activation and IgG deposition in the glomerular basement membrane. In sharp contrast, none of these signs were observed in F1 mice, which were injected with CD28KO spleen cells.

The CD28-mediated T-cell costimulatory pathway plays a pivotal role in the development of polyclonal B-cell activation, autoantibody production, and an immune complex glomerulonephritis. We propose that CD28KO mice are useful clues in examining the pathogenesis of experimental lupus nephritis.