Mouse targets undergo double-strand DNA fragmentation when exposed to syngeneic or xenogeneic LAK cells whereas human targets undergo single-strand breaks.
A number of recent studies have shown that mouse target cells (TC) of hematopoietic origin, when exposed to cytotoxic lymphocytes, undergo double-stranded DNA fragmentation. The cause and relevance of the fragmentation remain controversial. In this study we generated a number of mouse (M-LAK) and human LAK (H-LAK) cells and exposed them to a variety of mouse and human TC. YAC and SP/2, 2 mouse TC underwent rapid and extensive fragmentation when lysed by either human or mouse LAK whereas K562 and Daudi, 2 human TC, under the same conditions did not. All 4 TC, however, were killed quite efficiently. Next we labeled TC with 125I-deoxyuridine, exposed them to LAK cells for up to 18 h and loaded the LAK:TC mixtures over an alkaline linear sucrose gradient. After lysing the cells with a lysis buffer containing Triton X-100 we showed that K562 that had been in contact with LAK cells for more than 1 h exhibited single-strand nicks. However, whereas double-strand fragmentation preceded chromium release (lytic activity), the appearance of single-strand nicks did not. Finally, protein synthesis was not required for either type of fragmentation. In summary, we have demonstrated that: (1) the ability to undergo DNA fragmentation is a property of the TC rather than the effector cells that mediated their death, and (2) K562 and Daudi, 2 human TC, undergo single-strand nicks when lysed by LAK cells whereas SP/2 and YAC, 2 mouse TC undergo double-strand fragmentation when exposed to the same syngeneic or xenogeneic effector cells.
Brahmi
Z
Z
Department of Medicine, Indiana University School of Medicine, Indianapolis.
Tomita
A
A
Hommel-Berrey
G
G
Woodard
G
G
Morse
P
P
D000818:Animals; D002499:Centrifugation, Density Gradient; D004249:DNA Damage / Q000276:immunology; D004277:DNA, Single-Stranded / Q000276:immunology; D004587:Electrophoresis, Agar Gel; D006801:Humans; D015979:Killer Cells, Lymphokine-Activated / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology; D014407:Tumor Cells, Cultured
D004277:DNA, Single-Stranded