Mink cell focus-forming murine leukemia virus infection induces apoptosis of thymic lymphocytes.
In a previous study we identified the subpopulations of thymus cells that were infected by the lymphomagenic MCF13 murine leukemia virus (MLV) (F. K. Yoshimura, T. Wang, and M. Cankovic, J. Virol. 73:4890-4898, 1999) and observed an effect on thymus size by virus infection. In this report we describe our results which demonstrate that MCF13 MLV infection of thymuses reduced the number of T lymphocytes in this organ. Histological examination showed diffuse lymphocyte depletion, which was most striking in the CD4(+) CD8(+) lymphocyte-enriched cortical zone. Consistent with this, flow cytometric analysis showed that the lymphocytes which were depleted were predominantly the immature CD3(-) CD4(+) CD8(+) and CD3(+) CD4(+) CD8(+) cells. A comparison of the percentages of live, apoptotic, and dead cells of the gp70(+) and gp70(-) thymic lymphocytes suggested that this effect on thymus cellularity is a result of virus infection. Studies of the survival of thymic T lymphocytes in culture showed that cells from MCF13 MLV-inoculated mice underwent greater apoptosis and death than cells from control animals. Assays for apoptosis included 7-amino-actinomycin D staining, DNA fragmentation, and cleavage of caspase-3 and poly(ADP-ribose) polymerase proenzymes. Our results suggest that apoptosis of thymic lymphocytes by virus infection is an important step in the early stages of MCF13 MLV tumorigenesis.
Department of Immunology and Microbiology and the Karmanos Cancer Institute, Wayne State University, Detroit, Michigan 48201, USA. fyoshi@med.wayne.edu
F K
FK
Yoshimura
T
T
Wang
F
F
Yu
H R
HR
Kim
J R
JR
Turner
D000818:Animals; D017209:Apoptosis; D015496:CD4-Positive T-Lymphocytes / Q000473:pathology / Q000821:virology; D018414:CD8-Positive T-Lymphocytes / Q000473:pathology / Q000821:virology; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002478:Cells, Cultured; D053938:DNA Fragmentation; D004792:Enzyme Precursors / Q000378:metabolism; D005434:Flow Cytometry; D007942:Leukemia, Experimental / Q000276:immunology / Q000473:pathology* / Q000821:virology; D051379:Mice; D008806:Mice, Inbred AKR; D008908:Mink Cell Focus-Inducing Viruses / Q000276:immunology*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D012192:Retroviridae Infections / Q000276:immunology / Q000473:pathology* / Q000821:virology; D013601:T-Lymphocytes / Q000473:pathology / Q000821:virology*; D013950:Thymus Gland / Q000473:pathology / Q000821:virology; D014412:Tumor Virus Infections / Q000276:immunology / Q000473:pathology* / Q000821:virology
D004792:Enzyme Precursors; D011065:Poly(ADP-ribose) Polymerases; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases