Takashi Agui

Inheritance of T helper immunodeficiency (thid) in LEC mutant rats

LEC rat was originally established at the Center for Experimental Plants and Animals, Hokkaido University, as a mutant strain that spontaneously develops hepatic injury and hepatocarcinoma. The gene responsible for these hepatic effects was designated as hts (Masuda et al. 1988). Thereafter, it was reported that LEC rats have another recessive mutational gene, Igsr-1, which causes decrease in serum IgG level but not in Igm or IgA level (Matsumoto et al. 1989). Most recently, we found a deficiency in CD4 + T-cells in LEC rats and demonstrated it is caused by an arrest of the maturation from CD4+8 + to CD4+8 cells in the thymus (Agui et al. 1990). In this study, we report the genetic characterization of CD4 + Tcells deficiency and its linkage relationship with Igsr-1 locus or other loci reorted already. LEC/Tj (RT1.A) and WKAH/Tj (RT1.A k) inbred rats have been bred in our laboratory under specific pathogen free conditions. BN/Kyo (RT1.A n) rats were kindly supplied by Dr. J. Yamada, University of Kyoto, Japan. LEC mutant rats used in this experiment were highly inbred (over 48 generations of brother and sister mating). LEC, WKAH, (WKAH x LEC)F 1 hybrids, and (WKAH x LEC)F 1 x LEC and (BN x LEC)F1 x LEC backcrosses animals were used in genetic analyses. CD4 + T-cells from thymuses and peripheral organs of 1-12 months old rats were analyzed by either singleor two-color flow cytometry (FACScan, Becton Dickinson, Mountain View, California) using fluorescein isothiocyanate (FITC)-conjugated W3/25 monoclonal antibody (mAb) or FITC-conjugated W3/25 and phycoerythrin (PE)-conjugated OX8 mAbs, respectively. Serum IgG levels of (WKAH x LEC)F1 x LEC one-month-old rats

Chromosomal assignments of genes for rat glutathione S-transferase Ya (GSTA1) and Yc summits (GSTA2)

Chromosomal assignments of genes for rat glutathione S-transferase Ya (GSTA1) and Yc subunits (GSTA2) were performed by Southern blot analyses of somatic cell hybrid DNAs.GSTA1 and GSTA2 were assigned to rat chromosomes 8 and 9, respectively.

Elevation of metallothionein gene expression associated with hepatic copper accumulation in Long-Evans Cinnamon mutant rat.

The mechanism of the metallothionein (MT) gene expression was investigated in a mutant rat, LEC, which exhibits an abnormal accumulation of copper in hepatocytes. The levels of MT mRNA were extremely high and correlated with the hepatic copper concentrations in LEC rat liver. Gel retardation assays in nuclear extracts from LEC rat liver showed an increase in the copper-dependent binding proteins, which bind to the metal responsive element (MRE) of the MT gene. These results suggest that the high intracellular copper accumulation results in the elevation of the MT gene expression through increasing a putative trans-activating factor in LEC rat.

Chromosome assignments of genes for rat ceruloplasmin (CP) and metallothionein (MT)

Chromosome assignments of the genes for rat ceruloplasmin (CP) and metallothionein (MT) were performed by analyzing somatic cell hybrid DNAs with the polymerase chain reaction (PCR), using primers specific for rat genes. The genes for CP and MT were assigned to rat chromosomes 2 and 19, respectively.

Arrest of Maturation of Helper T Cells in LEC Rats

T-cell maturation and its acquisition of the repertory reactive to foreign antigens in the thymus is one of the important topics in recent immunology. T cells are mainly categorized into two subtypes, helper and killer cells. Most of the helper T cells express CD4 antigens on their cellular surface, while killer T cells express CD8 antigens. These two surface antigens play an important role for the adherence to the target cells in helping the T-cell receptor for antigens (TCR) recognize major histocompatibility complex (MHC) antigens. Recently, differentiation of T cells within the thymus has been clarified by using these two surface marker antigens. Bone marrow-derived pre-T cells do not express either CD4 nor CD8 antigen. They express CD8 antigen first, but at this time they still do not express TCR/CD3 antigen complex and are regarded as an immature type. Immature CD8+ cells next express CD4 antigen and the TCR/CD3 antigen complex. This population of the thymocytes (CD4+8+) are thought to receive both negative and positive selections. CD4+8+ cells, which escaped from the clonal deletion, differentiate into mature single-positive cells (either CD4+8- or CD4-8+ cells). This sequential maturation of T cells requires the aid of thymic stromal cells.