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.
el Demellawy
M
M
Research Unit, Institute of Sera and Vaccines, Cairo, Egypt.
el Ridi
R
R
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