title: Evidence for major alterations in the thymocyte subpopulations in murine models of autoimmune diseases.
abstract: Thymocytes can be divided into four major subpopulations: CD4+CD8+ (double-positive), CD4-CD8- (double-negative), CD4+CD8- (CD4+) and CD4-CD8+ (CD8+) cells. Recent studies have shown that T-cell development in the thymus progresses as: CD4-CD8(-)----CD4+CD8(+)----CD4+ or CD8+ cells. In the present study we investigated these and other subpopulations of thymocytes in autoimmune MRL(-)+/+, MRL-lpr/lpr, C57BL/6-lpr/lpr, BXSB and NZB mice before (1-month old) and after (4-6-months old) the onset of lymphadenopathy and autoimmune disease. All the autoimmune strains at one month of age and other H-2, sex and age-matched controls (C3H, DBA/2, and C57BL/6) demonstrated normal proportions of thymocyte subsets with approximately 75% double-positive cells, 5-7% double-negative cells, 11-15% CD4+ cells and 3-5% CD8+ cells. By 4-6 months of age, MRL(-)+/+ mice demonstrated a moderate increase in double-negative cells (approximately 13%) and a decrease in double-positive cells (approximately 46%). Interestingly, in the presence of the lpr gene, as seen in MRL-lpr/lpr mice, the double-negative cells increased to approximately 47% and the double-positive cells decreased to approximately 16%. In contrast, 4-6-month-old C57BL/6-lpr/lpr mice failed to demonstrate any alterations in the thymocyte subsets thereby suggesting that background genes, in addition to the lpr gene, played a role in the thymocyte differentiation. BXSB male mice with severe lymphadenopathy behaved very similarly to MRL-lpr/lpr mice, inasmuch as their thymus contained approximately 48% double-negative cells and only approximately 8% double-positive cells. In contrast to MRL-lpr/lpr and BXSB strains, NZB mice at 6 or 10 months of age had normal composition of thymocyte subsets. In MRL and BXSB animals, although there was a significant increase in CD4+ cells (approximately 23-33%), due to a consequent increase in CD8+ cells (approximately 11%), the ratio of CD4+:CD8+ cells remained 2-3:1, similar to that seen in normal mice. Furthermore, using the J11d marker expressed by the majority of the double-negative and all double-positive thymocytes but not by mature functional T cells, we confirmed the above findings and demonstrated further that MRL-lpr/lpr mice at 4-6 months of age had an increased percentage of J11d- double-negative cells and a decrease in J11d+ double-negative cells.(ABSTRACT TRUNCATED AT 400 WORDS)
authors.affiliation: Department of Biology, Virginia Polytechnic Institute and State University, Blacksburg 24061.
authors.forename: V N
authors.initials: VN
authors.lastname: Kakkanaiah
authors.forename: R H
authors.initials: RH
authors.lastname: Pyle
authors.forename: M
authors.initials: M
authors.lastname: Nagarkatti
authors.forename: P S
authors.initials: PS
authors.lastname: Nagarkatti
mesh_terms: D000818:Animals; D000943:Antigens, Differentiation / Q000096:biosynthesis; D000945:Antigens, Differentiation, T-Lymphocyte / Q000096:biosynthesis; D001323:Autoantibodies / Q000276:immunology; D001327:Autoimmune Diseases / Q000276:immunology*; D015704:CD4 Antigens / Q000096:biosynthesis; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D016827:CD8 Antigens; D002469:Cell Separation; D004195:Disease Models, Animal; D005260:Female; D005434:Flow Cytometry; D006825:Hybridomas / Q000276:immunology; D008198:Lymph Nodes / Q000276:immunology; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D013601:T-Lymphocytes / Q000276:immunology*; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology; D013950:Thymus Gland / Q000276:immunology*
chemical_list: D000943:Antigens, Differentiation; D000945:Antigens, Differentiation, T-Lymphocyte; D001323:Autoantibodies; D015704:CD4 Antigens; D016827:CD8 Antigens