Donor cell persistence and activation-induced unresponsiveness of peripheral CD8+ T cells

Abstract

We studied the impact of the duration of donor cell persistence on CD8+ T cell responsiveness after adoptive transfer of antigen-expressing lymphoid cells. Naive or immunized female mice were treated by adoptive transfer of spleen cells from mice ubiquitously expressing a lymphocytic choriomeningitis virus-derived cytotoxic T lymphocyte (CTL) epitope (gp33-41) either alone or in combination with the male H-Y antigen providing additional antigenic CTL and T helper cell determinants. Low doses of male spleen cells (or sorted B cells) primed CTL, while high doses of the same cells rendered them unresponsive. CTL unresponsiveness induced by high numbers of male spleen cells was dependent upon prolonged persistence of antigen-expressing donor cells. Unresponsive CTL reverted to a state of activation when the duration of donor cell chimerism was limited. Memory CTL could be rendered unresponsive if antigen-expressing donor cells were allowed to persist. These results suggest that, irrespective of the type of antigen-presenting cell and the functional state of the responding T cell, activation and unresponsiveness can represent two different outcomes critically determined by quantitative and kinetic differences of antigen persistence.

Perforin-independent regulation of dendritic cell homeostasis by CD8+ T cells in vivo: implications for adaptive immunotherapy

“…It is possible that the previously observed negative feedback regulation via perforin in vivo is restricted to very strong stimuli, such as superantigen stimulation [29], virus infection [29], or severe graft-versus-host disease [19] and that during the relatively weak and transient CTL activation via DC other molecules compensate for the potential regulatory function of perforin. It is important to note that the absence of perforin, Fas or TNFR alone has also only a marginal effect on the elimination of lymphocytes by CTL in vivo [30], further supporting the notion killing of lymphocytes and myeloid cells is a multifactorial process.…”

Exhaustion of cytotoxic T cells during adoptive immunotherapy of virus carrier mice can be prevented by B cells or CD4+ T cells

“…The T cells were only exhausted, if they were confronted with high systemic virus loads for a prolonged period of several days. In the context of previous studies [21,[48][49][50][51], the duration of antigenic stimulation is therefore one of the key factors in determining the fate of the transferred T cells.…”

“…No neutralizing antibodies to LCMV could be demonstrated in these mice. Virus persistence was not due to CTL epitope escape mutations, since virus isolated from the spleen of these mice was still recognized by in vitro generated TCRtg effector cells when used to infect target cells in a 51 Cr-release assay (data not shown). The same kinetics of virus titers and CD8 + T cell exhaustion was obtained after transfer of naive cells from TCRtg mice crossed to the lpr/lpr background, indicating that the limited persistence of donor T cells was not due to fas mediated apoptosis (data not shown).…”

“…Two months after transfer the mice were sacrificed. Virus titers were then determined in several organs, tracer TCRtg donor CD8 + T cells were counted by flow cytometry and CTL were studied functionally in 51 Cr-release assays after in vitro restimulation.…”

“…For determination of ex vivo cytolytic activity, spleen cell suspensions were prepared and restimulated for 5 days on thioglycolate induced LCMV-WE infected macrophages with addition of 2.5% ConA supernatant. After restimulation the cultured cells were used at various dilutions of the standard culture as effector cells in a standard five hour 51 Cr-release assay [60]. EL-4 target cells were coated with the LCMV gp 33-41 (10 -6 molar for 2 h) or left untreated.…”