Mechanisms of gene therapy for tolerance: B7 signaling is required for peptide-IgG gene-transferred tolerance induction.
LPS-activated B cells, transduced with IgG fusion proteins, are highly tolerogenic APCs. To analyze the mechanisms for this B cell-delivered gene therapy, we first followed the fate of CFSE-labeled B cell blasts. These cells primarily localized to the spleen, where a small population persisted for at least 1 mo after injection. By day 7 after injection, approximately 95% of the transduced cells had divided at least once, presumably an effect of the in vitro LPS activation into the cycle, because resting cells did not divide. B cells from gld donors were not tolerogenic, initially suggesting a role for Fas ligand (FasL) in tolerance. Because transduced normal B cells expressed only low levels of FasL and did not kill Fas-expressing Jurkat or A20 B lymphoma cells in vitro, these data suggest that gld B cells are not tolerogenic due to unique characteristics of these B cells rather than the lack of functional FasL expression. The transduced B cell blasts displayed significant up-regulation of both B7 costimulatory molecules, and B7.2 up-regulation was maintained through day 7 in vivo. When B cells from B7 knockout donors were transduced to express Ig fusion proteins, they were not tolerogenic in two different mouse strains and Ag models. Moreover, anti-B7 Ab blocked tolerance induction in this model, a result consistent with a role for B7 in tolerance induction. We propose that tolerance may be induced in this model by B7-driven negative regulatory signaling, but tolerance is maintained by a lack of signal 2, because expression of B7 is eventually lost in vivo.
Department of Immunology, George Washington University Medical Center, Washington, DC 20037, USA. litzingm@mail.nih.gov
Mary T
MT
Litzinger
Yan
Y
Su
Tie Chi
TC
Lei
Nadejda
N
Soukhareva
David W
DW
Scott
D000818:Animals; D017209:Apoptosis / Q000235:genetics / Q000276:immunology; D016175:B-Lymphocyte Subsets / Q000166:cytology / Q000276:immunology / Q000378:metabolism / Q000637:transplantation; D018122:B7-1 Antigen / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D018920:Coculture Techniques; D015316:Genetic Therapy / Q000379:methods; D006801:Humans; D007108:Immune Tolerance / Q000235:genetics*; D007074:Immunoglobulin G / Q000008:administration & dosage / Q000235:genetics* / Q000502:physiology; D019169:Jurkat Cells; D008070:Lipopolysaccharides / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D041681:NIH 3T3 Cells; D010446:Peptide Fragments / Q000008:administration & dosage / Q000235:genetics* / Q000276:immunology*; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology*; D014161:Transduction, Genetic / Q000379:methods
D018122:B7-1 Antigen; D007074:Immunoglobulin G; D008070:Lipopolysaccharides; D010446:Peptide Fragments