Selective depletion of marrow-T cytotoxic lymphocytes (CD8) in the prevention of graft-versus-host disease after allogeneic bone-marrow transplantation

Reversal of CD8 T-cell-mediated mucocutaneous graft-versus-host-like disease by the JAK inhibitor tofacitinib

The utility of allogeneic hematopoietic stem cell transplantation is limited by graft-versus-host disease (GVHD), a significant cause of morbidity and mortality. Patients with GVHD exhibit cutaneous manifestations with histological features of interface dermatitis followed by scleroderma-like changes. JAK inhibitors represent a class of immunomodulatory drugs that inhibit signaling by multiple cytokines. Herein we report the effects of tofacitinib in a murine model of GVHD. Oral administration of tofacitinib prevented GVHD-like disease manifested by weight loss and mucocutaneous lesions. More importantly, tofacitinib was also effective in reversing established disease. Tofacitinib diminished the expansion and activation of murine CD8 T cells in this model, and had similar effects on IL-2-stimulated human CD8 T cells. Tofacitinib also inhibited the expression of IFN-γ-inducible chemoattractants by keratinocytes, and IFN-γ-inducible cell death of keratinocytes. Tofacitinib may be an effective drug for treatment against CD8 T-cell-mediated mucocutaneous diseases in patients with GVHD.

T cell depletion in paediatric stem cell transplantation

Haematopoietic stem cell transplantation (HSCT) can be a curative procedure for a growing number of paediatric diseases, but as the indications for HSCT grow, so does the need to find suitable stem cell donors. When the preferred option of a genoidentical sibling donor is not available alternative donors, including unrelated adult or umbilical cord blood donors, or haploidentical related donors may be considered. Outcome following alternative donor HSCT has improved over the past 20 years but graft-versus-host disease (GvHD) remains a significant obstacle. T cell depletion (TCD) for non-genoidentical grafts aims to reduce the morbidity and mortality associated with GvHD, but this intervention has not led directly to improved survival due to delayed immune reconstitution and increased infections, graft rejection and increased rates of disease relapse. Limited data from the paediatric population, however, suggest some encouraging results for children undergoing haploidentical HSCT: a move from positive selection of CD34(+) haematopoietic stem cells towards negative depletion of specific cell subsets in order to retain useful accessory cells within the graft appears to enhance immune reconstitution and improve disease-free survival. Here we review recent paediatric outcome data for T cell-depleted HSCT, explore the role of serotherapy in conditioning regimens and look at future possibilities to improve outcome, including novel allodepletion techniques, suicide gene therapy and pathogen-specific immunotherapy.

Cytokine profiles in various graft-versus-host disease target organs following hematopoietic stem cell transplantation

Previous studies using genetic-deficient murine models suggest that different T-helper subsets may contribute to different types of tissue damages in graft-versus-host disease (GvHD). However, there is limited information available on the distribution of T-helper cytokines in the various GvHD target tissues. In the current study, an acute GvHD murine model was set up to directly assess the in situ cytokine profiles in various GvHD tissue lesions; in addition, we also studied GvHD tissues from patients who had undergone bone marrow transplantation procedures. We observed that interferon-γ (IFN-γ was dominant in murine liver and gastrointestinal tissue lesions, whereas IFN-γ and interleukin 17 (IL-17) were abundant in murine skin lesions. Furthermore, in human GvHD tissues, interleukin 4 (IL-4) and IFN-γ were predominant in liver lesions and colon lesions, respectively, while no specific cytokine was prevalent in human GvHD skin lesions. In addition, a low ratio of CD4(+) T helper (Th) versus CD8(+) T cytotoxic (Tc) cells in human GvHD tissue lesions, especially in the liver, was detected, and this contrasts with the situation in murine GvHD tissues where CD4(+) Th cells were predominant. Dual staining for CD markers and cytokine expression showed that IFN-γ-secreting T cells were enriched in all murine GvHD target tissue lesions, and Tc1 and Tc2 cells were predominant in human GvHD colon and liver sections, respectively. However, IFN-γ(+) Th1, IL-17(+) Th17, IFN-γ(+) Tc1, and IL-17(+) Tc17 cells were slightly more frequent in human skin lesions compared to IL-4(+) Th2 and IL-4(+) Tc2 cells. To sum up, these results suggest that differences in cytokine imbalances may significantly contribute to tissue-specific pathogenesis in GvHD target organs, and CD8(+) Tc cells may play an important role in human GvHD induction.

Human minor histocompatibility antigens: new concepts for marrow transplantation and adoptive immunotherapy

Bone marrow transplantation (BMT) is the present treatment for hematological malignancies. Two major drawbacks of allogeneic BMT are graft-versus-host disease (GVHD) and leukemia relapse. The use of HLA-matched siblings as marrow donors results in the best transplant outcome. Nonetheless, the results of clinical BMT reveal that the selection of MHC-identical donors' bone marrow (BM) is no guarantee for avoiding GVHD or ensuring disease-free survival even when donor and recipient are closely related. It is believed that non-MHC-encoded so-called minor histocompatibility antigens (mHag) are involved in both graft-versus-host and graft-versus-leukemia activities. The recent new insights into the chemical nature of mHag not only reveal their physiological function but, more importantly, provide insights into their role in BMT. Together with the information on the human mHag genetics and tissue distribution gathered in the past, we may now apply this knowledge to the benefit of human BMT. Directly relevant is the utility of mHag molecular typing for diagnostics in BM donor selection. Most promising is the use of mHag-specific cytotoxic T cells for adoptive immunotherapy of leukemia.

The combined use of soybean agglutinin and immunomagnetic beads for T lymphocyte subset depletion of bone marrow allografts: a laboratory analysis

The prevention of graft-versus-host disease by T-lymphocyte depletion of allografts prior to bone marrow transplantation has resulted in an increase in graft failure/rejection and relapse of disease. Evidence for the selective roles of specific T-lymphocyte subsets in each of the engraftment, graft-versus-host disease, and disease relapse processes has been presented, but sufficient clinical verification to support any hypothesis in this regard is lacking. In this paper we describe a convenient and highly flexible clinical laboratory method for depletion of specific T-lymphocytes in controllable quantities by the use of select monoclonal antibodies. Almost 3 log10 removal of CD2+ and CD8+ cells without significant loss of hematopoietic progenitors (CFU-GM, BFU-E, and CD34+ cells) can be reproducibly achieved. This method, employing soybean agglutination and immunomagnetic beads, is potentially adaptable to depletion of any cell subset or any tumor cell for which unique cell-surface antigen characteristics have been defined. In addition, our protocol is equally suited to the positive selection of stem cells and hematopoietic progenitors bearing the CD34 surface antigen.

Minor histocompatibility antigens, defined by graft-vs.-host disease-derived cytotoxic T lymphocytes, show variable expression on human skin cells

Little is known on the effector mechanisms inducing the cutaneous lesions observed during acute graft-vs.-host disease (aGvHD) after allogeneic bone marrow transplantation (BMT). Histological findings have indicated that infiltrating CD8+ lymphocytes probably play a role. We addressed the question of whether host minor histocompatibility (mH) antigen-reactive cytotoxic T lymphocytes (CTL) could account for this phenomenon via direct lysis of the epidermal cell layer. Six CTL clones, obtained from peripheral blood lymphocytes of patients suffering from aGvHD, each recognizing a well-characterized MHC class I-restricted mH antigen epitope, were tested on cultured keratinocytes of nine MHC and mH antigen-typed donors. Four of six mH antigen-specific CTL clones lysed unstimulated MHC class I-expressing, as well as recombinant interferon-gamma (rIFN-gamma)-activated, ICAM-1, MHC class I- and II-expressing keratinocytes. Two strongly cytolytic CTL clones showed no recognition of keratinocytes of donors whose phytohemagglutinin-activated T cell lines were readily lysed. With respect to a GvHD, the results imply that some class I-restricted CTL obtained from peripheral blood lymphocytes of a GvHD patients have the in vitro potential to destroy resting as well as IFN-gamma-activated epidermal cells, whereas others do not. In other words, CTL-defined human mH antigens vary with respect to their expression in the skin. It is intriguing that those minor H antigens which cannot be detected on human keratinocytes in vitro are those known to be associated with the occurrence of GvHD.