Identification of systemically expanded activated T cell clones in MRL/lpr and NZB/W F1 lupus model mice

CD4+ T lymphocytes play an important role in the pathogenesis of systemic lupus erythematosus (SLE). To characterize the clonal expansion of CD4+ T cells in murine lupus models, we analysed the T cell clonality in various organs of young and nephritic MRL/lpr and NZB/W F1 mice using reverse transcription–polymerase chain reaction (RT-PCR) and subsequent single-strand conformation polymorphism (SSCP) analysis. We demonstrated that some identical T cell clonotypes expanded and accumulated in different organs (the bilateral kidneys, brain, lung and intestine) in nephritic diseased mice, and that a number of these identical clonotypes were CD4+ T cells. In contrast, young mice exhibited little accumulation of common clones in different organs. The T cell receptor (TCR) Vβ usage of these identical clonotypes was limited to Vβ2, 6, 8·1, 10, 16 and 18 in MRL/lpr mice and to Vβ6 and 7 in NZB/W F1 mice. Furthermore, some conserved amino acid motifs such as I, D or E and G were observed in CDR3 loops of TCRβ chains from these identical CD4+ clonotypes. The existence of systemically expanding CD4+ T cell clones in the central nervous system (CNS) suggests the involvement of the systemic autoimmunity in CNS lesions of lupus. FACS-sorted CD4+CD69+ cells from the kidney displayed expanded clonotypes identical to those obtained from the whole kidney and other organs from the same individual. These findings suggest that activated and clonally expanded CD4+ T cells accumulate in different tissues of nephritic lupus mice, and these clonotypes might recognize restricted T cell epitopes on autoantigens involved in specific immune responses of SLE, thus playing a pathogenic role in these lupus mice.