Richard A. Banas

Immunogenicity and immunomodulatory effects of amnion-derived multipotent progenitor cells

This is the first study on the immunologic properties of a clinically relevant population of cells derived from the amnion of human placenta. Unlike other cells from the amnion, these amnion-derived multipotent progenitor cells (AMP cells), from human amnion, grow in serum-free conditions and have never been cultured in the presence of medium containing animal-derived components. This study reports the immunologic characteristics of AMP cells and their roles as immunomodulators. Characterization of AMP cells revealed the presence of major histocompatibility complex (MHC) class I but the lack of class II antigens and absence of co-stimulatory molecules B7-1 and B7-2. The nonclassical human leukocyte antigen (HLA)-G was expressed at low levels on cultured AMP cells. Expression was significantly increased after interferon-gamma (IFN-gamma) treatment. Cultured peripheral blood mononuclear cells did not respond to irradiated AMP cells, indicated by lack of proliferation as measured by standard mixed lymphocyte reaction. Culturing AMP cells with IFN-gamma did not reverse this result and did not upregulate class II expression. The AMP cells were shown to have immunomodulatory capabilities by inhibiting peripheral blood mononuclear cell proliferative responses to mitogen, alloantigen, and recall antigen, but the AMP cells were unable to inhibit preactivated T-cell blast response to growth factor media. This immunomodulatory effect of AMP cells was found to be dependent on cell-to-cell contact.

Three years of follow-up of bone marrow-augmented organ transplant recipients: The impact on donor-specific immune modulation ☆

The discovery of the presence of previously unsuspected microchimerism in successful longterm liver and kidney transplant recipients prompted us to postulate that these cells are essential for graft acceptance and the induction of donor-specific hyporeactivity.1–3 This observation provided the basis for the initiation of a new therapeutic strategy which involved infusion of donor bone marrow (BM) cells under conventional immunosuppressive treatment with tacrolimus and prednisolone.4 The initial outcome of sequential in vitro immunologic evaluations performed to determine the development of donor-specific hyporeactivity in the first 15 BM-augmented and 16 contemporaneous controls has been described previously.5,6 We report here the immune profile of 102 BM-augmented and 57 control patients who were at least 6 months posttransplantation.

Amnion-derived multipotent progenitor cells inhibit blood monocyte differentiation into mature dendritic cells.

Cells derived from the placenta have become the focus of extensive research concerning their ability to be used for regenerative medicine or cellular therapies. In a previous study, we characterized amnion-derived multipotent progenitor cells, or AMP cells, by in vitro methods and showed they were able to inhibit antigen-specific T-cell proliferation in a cell-to-cell contact-dependent fashion. Here we examine specific mechanisms involved in immunomodulation by AMP cells. We found that AMP cells significantly inhibited monocyte-derived myeloid dendritic cell (DC) maturation when placed in coculture. Cocultured monocytes retained the nondifferentiated macrophage marker CD14 while exhibiting significant reduction in DC maturation markers CD83 and CD1a, indicating an immature DC maturation state that is pivotal in determining its immune stimulatory or regulatory status. This effect was again dependent on cell-to-cell contact interaction. We also found a significant shift in cytokines present in the microenvironment of cocultures, which indicated a regulatory DC function rather than a stimulatory cell type. Here supernatants taken from AMP cell/monocyte cocultures yielded significant levels of regulatory cytokines, such as PGE2, IL-6, IL-10, and MIC-1. The soluble form of HLA-G was also found at higher levels in cocultures. In contrast, supernatants contained significantly less amounts of the T-cell-stimulating factor IL-12, which is normally produced by activated DCs. Interestingly, cocultured monocytes acquired significant expression of HLA-G on their cell surface over time. HLA-G has multifaceted immunological implications and may be a key molecule in influencing these cells to behave as regulatory DCs. Together, the influence of AMP cells on maturing DCs may favor a regulatory pathway that can be useful for therapeutic applications for immune-mediated disorders or transplantation therapies.

Clinical Significance of Cytomegalovirus-Specific T Helper Responses and Cytokine Production in Lung Transplant Recipients

Cytomegalovirus (CMV) disease continues to be a major problem for lung transplant recipients. In CMV-seropositive individuals, we detected two types of CMV-specific responses: a self-restricted response stimulated by soluble CMV antigen (sCMV-Ag) and a non-self-restricted response induced by CMV-infected cells (cCMV-Ag). Lung transplant recipients who develop the CMV-specific self-restricted T helper response have a low risk of recurrent CMV disease. In contrast, during CMV disease, lung transplant recipients exhibit only the non-self-restricted T helper responses. We characterized the T cell activation and the kinetics of cytokine production of sorted CD4+ and CD8+ T cells from PBLs of CMV seropositive donors. The two types of CMV antigens induced cytokine production in both T cell subsets. We also performed competitive RT-PCR for Granzyme B (GB) in BAL cells of lung transplant recipients prior to, during and following CMV disease. CMV disease was associated with increase in GB gene expression when was accompanied by acute cellular rejection while it remained low in patients with CMV disease that did not have a complicated course. In summary, CMV-activated T cells within the allograft may produce inflammatory cytokines and effector molecules that may promote allograft rejection.