Soluble and membrane-bound TNF-alpha are involved in the cytotoxic activity of B cells from tumor-bearing mice against tumor targets.
Splenic B cells from BALB/c mice bearing mammary adenocarcinomas are capable of performing Ab-dependent cellular cytotoxicity. Effector-target conjugation after 18 h results in minimal cytoplasmic damage, whereas extensive nuclear disintegration is observed. To determine whether splenic B cells from tumor-bearing mice can effect direct cytotoxicity against tumor cells, L929 and WEHI 164 cells were used as targets. B lymphocytes from tumor-bearing mice, but not from normal animals, were capable of lysing these two types of tumor cells. However, only a low level of cytotoxicity could be detected when the nontumorigenic 3T3 cells were used as targets. To elucidate the mechanism of cytotoxicity of these killer B cells, RNase protection assays were performed using perforin, granzyme A, TNF-alpha, and lymphotoxin probes. No perforin, granzyme A, or lymphotoxin RNA could be detected in purified preparations of B cells from normal and tumor-bearing mice. B cells from normal mice did not have TNF-alpha RNA. In contrast, B cells from tumor bearers expressed TNF-alpha RNA. TNF-alpha could be detected in supernatants from both unstimulated and stimulated tumor bearers' splenic B cells, as measured by ELISA, and its lytic activity was neutralized by anti-TNF-alpha Ab. Western blots revealed the presence of TNF-alpha on the surface of the killer B cells. Paraformaldehyde-fixed B cells from tumor-bearing mice but not from normal animals were able to lyse TNF-alpha-sensitive tumor targets. This cytotoxicity was neutralized by anti-TNF-alpha Ab. These results suggest that TNF-alpha in soluble and membrane-bound forms may be involved in the mechanism of cytotoxicity exerted by B cells from tumor-bearing mice.
Lopez-Cepero
M
M
Department of Microbiology and Immunology, University of Miami School of Medicine, FL 33136.
Garcia-Sanz
J A
JA
Herbert
L
L
Riley
R
R
Handel
M E
ME
Podack
E R
ER
Lopez
D M
DM
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D003602:Cytotoxicity, Immunologic; D005260:Female; D015870:Gene Expression; D053804:Granzymes; D007694:Killer Cells, Natural / Q000276:immunology*; D008233:Lymphotoxin-alpha / Q000235:genetics; D008297:Male; D008325:Mammary Neoplasms, Experimental / Q000276:immunology*; D008562:Membrane Glycoproteins / Q000235:genetics; D008565:Membrane Proteins / Q000502:physiology; D051379:Mice; D008807:Mice, Inbred BALB C; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D012333:RNA, Messenger / Q000235:genetics; D012697:Serine Endopeptidases / Q000235:genetics; D012995:Solubility; D014409:Tumor Necrosis Factor-alpha / Q000737:chemistry / Q000502:physiology*
D008233:Lymphotoxin-alpha; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D052899:Pore Forming Cytotoxic Proteins; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D054353:Perforin; D053804:Granzymes; D012697:Serine Endopeptidases