GM-CSF and IL-2 induce specific cellular immunity and provide protection against Epstein-Barr virus lymphoproliferative disorder.

Epstein-Barr virus-associated lymphoproliferative disease (EBV-LPD) is a potentially life-threatening complication in immune-deficient patients. We have used the severe combined immune deficient (SCID) mouse engrafted with human leukocytes (hu-PBL-SCID) to evaluate the use of human cytokines in the prevention of EBV-LPD in vivo. Daily low-dose IL-2 therapy can prevent EBV-LPD in the hu-PBL-SCID mouse, but protection is lost if murine natural killer (NK) cells are depleted. Here we demonstrate that combined therapy with human GM-CSF and low-dose IL-2 is capable of preventing EBV-LPD in the hu-PBL-SCID mouse in the absence of murine NK cells. Lymphocyte depletion experiments showed that human NK cells, CD8(+) T cells, and monocytes were each required for the protective effects of GM-CSF and IL-2 combination therapy. This treatment resulted in a marked expansion of human CD3(+)CD8(+) lymphocytes in vivo. Using HLA tetramers complexed with EBV immunodominant peptides, a subset of these lymphocytes was found to be EBV-specific. These data establish that combined GM-CSF and low-dose IL-2 therapy can prevent the immune deficiencies that lead to fatal EBV-LPD in the hu-PBL-SCID mouse depleted of murine NK cells, and they point to a critical role for several human cellular subsets in mediating this protective effect.

Trans vivo analysis of human delayed-type hypersensitivity reactivity.

There are clinical situations in which it may be advantageous to monitor delayed type hypersensitivity (DTH) responses, an index of cell-mediated immunity, without exposing patients directly to the challenge antigens. For example, transplant patients may be at risk for becoming sensitized to donor antigens if injected with donor antigen during traditional skin tests. We describe an alternative method for human DTH testing, which involves the transfer of human peripheral blood mononuclear cells plus antigen into the pinnae or footpads of naive mice. This induces a measurable DTH-like swelling response, which we refer to as the "trans vivo DTH response." As proof of principle, we provide data obtained during trans vivo DTH studies with tetanus toxoid, cytomegalovirus (CMV) and alloantigens. In general, human T cells must be co-localized with antigen and human macrophages to produce swelling responses, and such responses are antigen-specific and require prior antigen sensitization. Not only does this assay offer a simple, reliable clinical monitoring device, but it also provides a model with which to study the in vivo mechanisms of human DTH responses.