Age-associated decrease in proportion and antigen expression of CD8+/CD4+ thymocytes in BALB/c mice.
We studied the distribution of Thy-1.2+, CD8+ and CD4+ thymocytes in 3-, 6.5-, 12- and 18-month-old inbred BALB/c mice by staining cells with specific monoclonal antibodies (mAb) using indirect membrane immunofluorescence. The percentages of Thy-1.2+, CD8+, and CD4+ thymocytes did not vary with age until 12 months, but they exhibited at 18 months a highly significant decline. Staining thymocytes with mAb CD8 and CD4 alone or in a mixture allowed us to show that the age-related decline in proportions of CD8+ and CD4+ thymic cells is associated with the double positive (CD8+/CD4+, immature) subset. Most importantly, we observed a progressive age-related decrease in ratio of bright/dull Thy-1.2+, CD8+ and CD4+ thymocytes. The CD8+ and CD4+ thymocytes that did not adhere to peanut agglutinin (PNA-, which is supposed to represent the mature single positive subset) did not show any age-related change in the proportion of bright and dull cells. Therefore, we concluded that the double positive (CD8+/CD4+, immature, PNA+) thymocytes display reduced expression of CD8 and CD4 antigens with aging. The implications of these findings to the fundamental mechanisms of immunosenescence are discussed.
Research Unit, Institute of Sera and Vaccines, Cairo, Egypt.
M
M
el Demellawy
R
R
el Ridi
D000375:Aging / Q000276:immunology*; D000818:Animals; D000954:Antigens, Surface; D015704:CD4 Antigens; D016516:CD4-CD8 Ratio; D016827:CD8 Antigens; D005260:Female; D037102:Lectins; D008297:Male; D008562:Membrane Glycoproteins; D051379:Mice; D008807:Mice, Inbred BALB C; D019887:Peanut Agglutinin; D016176:T-Lymphocyte Subsets / Q000166:cytology / Q000276:immunology*; D018800:Thy-1 Antigens
D000954:Antigens, Surface; D015704:CD4 Antigens; D016827:CD8 Antigens; D037102:Lectins; D008562:Membrane Glycoproteins; D019887:Peanut Agglutinin; D018800:Thy-1 Antigens