SYNERGY AMONG LYMPHOID CELLS MEDIATING THE GRAFT-VERSUS-HOST RESPONSE : V. DERIVATION BY MIGRATION IN LETHALLY IRRADIATED RECIPIENTS OF TWO INTERACTING SUBPOPULATIONS OF THYMUS-DERIVED CELLS FROM NORMAL SPLEEN

Spleen cells from normal adult mice were injected into lethally irradiated adult syngeneic recipients. 24 h later, cell suspensions were prepared from the recipients' spleens or peripheral lymph nodes and tested either alone or combined for their capacity to elicit graft-versus-host (GVH) reactions in neonatal F1 recipients, using the Simonsen spleen weight assay. Either the lymph node-seeking subpopulation or the spleen-seeking subpopulation alone was markedly deficient in its ability to provide a GVH reaction when compared with the normal population from which it was derived. However, an appropriate mixture of the two had a reactivity characteristic of the parent population. Both subpopulations were sensitive to treatment with anti-θ antibody and complement in vitro. These results provide a convincing demonstration of the functional heterogeneity within the pool of thymus-derived cells present in a single normal lymphoid tissue. They strongly suggest that the normal expression of GVH reactivity of such a tissue involves an interaction among distinct subpopulations of thymus-derived cells

The Intracutaneous Growth of Murine Lymphomas: Epidermal Invasion Is Characteristic of Multiple Tumor Phenotypes

Affinity of lymphoid cells for the epidermis (epidermotropism) is characteristic of the cutaneous T-cell lymphomas, mycosis fungoides and the Sézary syndrome. Consistent with numerous studies indicating that mycosis fungoides is a neoplasm of OKT4+T8- (“helper/inducer”) T lymphocytes is the possibility that epidermotropism is a phenotypic hallmark of this subset of malignant T cells. This proposal was investigated in mice using 8 phenotypically characterized lymphomas of BALB/c origin: 3 histiocytic (phagocytic, lysozyme-positive, FcR+, Ig-, Thy 1-), 1 B-cell (IgM+, FcR+, Thy 1-), and 4 T-cell (Ig-, Thy 1+) lines, including 1 with markers of mouse helper/inducer T cells (Lyt1+23-), 2 with suppressor/cytotoxic markers (Lyt1-23+), and 1 with markers of immature thymocytes (Lyt1+23+). The intracutaneous growth pattern of these lines was studied on hematoxylin and eosin-stained sections through the centers of tumors obtained at times after intradermal injection into parallel groups of syngeneic mice. All of these lymphomas manifested variable epidermotropism that followed a typical sequence. Following dermal growth and spread to the dermal-epidermal junction, tumor cells appeared within the stratum spinosum. Subsequently, collections of cells appeared in spaces within the epidermis (Pautrier-like microabscesses) in tumors >2 cm in diameter, coincident with early epidermal necrosis. Thus, in this animal model it is clear that the intraepidermal invasion/growth does not correlate with the helper/inducer T-cell surface phenotype. These observations are nonetheless consistent with recent studies using monoclonal antibodies to cell surface antigens which have demonstrated a heterogeneity of lymphoid cell subsets within the epidermis in lesions of mycosis fungoides and of other malignant and benign dermatoses

SYNERGY AMONG LYMPHOID CELLS MEDIATING THE GRAFT-VERSUS-HOST RESPONSE : IV. SYNERGY IN THE GVH REACTION QUANTITATED BY A MORTALITY ASSAY IN SUBLETHALLY IRRADIATED RECIPIENTS

A mortality assay was used to quantitate graft-versus-host (GVH) reactions in sublethally irradiated (400 R) neonatal (C57BL/6 x BALB/c)F1 recipients of BALB/c lymphoid cells from various tissues. The probit of the 35 day cumulative per cent of mortality was a linear function of the logarithm of the cell inoculum for any tissue; reactivities of different tissues fell on a series of parallel lines. Peripheral blood leukocytes (PBL), the most active cells, were about 30 times as active as thymocytes, the least active cells studied; femoral lymph node cells and spleen cells were about 23 and 8 times as reactive as thymocytes, respectively. The average survival time of recipients of thymocytes who eventually died was nearly a week longer than that of recipients of comparably lethal numbers of PBL, lymph node, or spleen cells. Mixtures of PBL and thymocytes gave levels of 35 day mortality significantly greater than those expected if the reactivities of the mixture had been merely the sum of the reactivities of the components measured separately, thereby confirming in any assay independent of host splenomegaly the synergistic interaction of thymocytes and PBL in the GVH reaction. Both populations of cells in the mixture had to be allogeneic to the host in order to observe this synergy. The kinetics of cumulative mortality observed for mixtures of PBL and thymocytes were indistinguishable from those seen with thymocytes alone, indicating activation of the latter cell type. Finally, comparison of the relative abilities of different cell populations to cause splenomegaly on the one hand and lethal runting on the other has raised the possibility that expression of different effector functions of cell-mediated immune reactions may in fact be initiated by distinct cells

Origin and Function of Thy-1+ Dendritic Epidermal Cells in Mice

The epidermis of normal mouse skin incorporates a newly-recognized population of dendritic cells which express relatively large amounts of the cell surface glycoprotein, Thy-1 antigen. These cells, termed Thy-1+dEC, are distinct from both epidermal Langerhans cells (LC) and melanocytes, and they populate cutaneous sites in surface densities which range to as high as 580 cells/mm2, approximately two-thirds that of LC. Studies of lethally irradiated mice which were reconstituted with semiallogeneic bone marrow cells and mice which received grafts of semiallogeneic skin have demonstrated that some, if not all, Thy-1+dEC are of bone marrow origin, and that they are capable of migrating into epidermis from a vascular source. Thy-1+dEC expressed both asialo GM1 and a cell surface determinant recognized by the monoclonal antibody 20–10–5S, further suggesting their functions will be included among those normally ascribed to lymphoreticular cells. Isolation of epidermal cells with the Fluorescence Activated Cell Sorter (FACS) was successful in producing relatively pure populations of Thy-1+dEC and LC. Such technological advances as this should facilitate testing several hypotheses concerning the ultimate function of these cells, including the possibilities that they are antigen-presenting cells which selectively activate down-regulating signals, T lymphocytes, natural killer (NK) cells, or natural suppressor (NS) cells

Thy-1 Antigen-Bearing Dendritic Cells Populate Murine Epidermis

Two distinct cell populations, melanocytes and Langerhans cells (LC), have been recognized previously to possess dendritic configuration in normal mammalian epidermis. Employing immunofluorescence microscopy with monoclonal antibodies against Thy-1.2 antigen to identify cells in whole mounts of murine epidermis, we have identified a third dendritic cell population which differs from both LC and melanocytes. Thy-1 antigen- bearing (Thy-1+) epidermal cells are primarily dendritic, although round and angular forms may be found. They are distributed relatively evenly across skin surfaces, although densities vary greatly from site to site and from strain to strain. Densities were highest in ear epidermis from the pigmented strain B10.A (580 cells/ mm2), a value approaching that of epidermal LC, and were lowest in ear epidermis from the albino strain BALB/c (5 cells/mm2). Thy-1+ epidermal cells possess neither Ia antigens nor substantial amounts of melanin, and their surface distributions are disparate from those of both LC and mature melanocytes. We propose that at least some of these cells are T lymphocytes whose malignant counterparts account for cutaneous T-cell lymphomas

Resident Skin-specific γδ T Cells Provide Local, Nonredundant Regulation of Cutaneous Inflammation

The function of the intraepithelial lymphocyte (IEL) network of T cell receptor (TCR) γδ+ (Vγ5+) dendritic epidermal T cells (DETC) was evaluated by examining several mouse strains genetically deficient in γδ T cells (δ−/− mice), and in δ−/− mice reconstituted with DETC or with different γδ cell subpopulations. NOD.δ−/− and FVB.δ−/− mice spontaneously developed localized, chronic dermatitis, whereas interestingly, the commonly used C57BL/6.δ−/− strain did not. Genetic analyses indicated a single autosomal recessive gene controlled the dermatitis susceptibility of NOD.δ−/− mice. Furthermore, allergic and irritant contact dermatitis reactions were exaggerated in FVB.δ−/−, but not in C57BL/6.δ−/− mice. Neither spontaneous nor augmented irritant dermatitis was observed in FVB.β−/− δ−/− mice lacking all T cells, indicating that αβ T cell–mediated inflammation is the target for γδ-mediated down-regulation. Reconstitution studies demonstrated that both spontaneous and augmented irritant dermatitis in FVB.δ−/− mice were down-regulated by Vγ5+ DETC, but not by epidermal T cells expressing other γδ TCRs. This study demonstrates that functional impairment at an epithelial interface can be specifically attributed to absence of the local TCR-γδ+ IEL subset and suggests that systemic inflammatory reactions may more generally be subject to substantial regulation by local IELs

The Distinct Contributions of Murine T Cell Receptor (TCR)γδ+ and TCRαβ+ T Cells to Different Stages of Chemically Induced Skin Cancer

Epithelial tissues in which carcinomas develop often contain systemically derived T cell receptor (TCR)αβ+ cells and resident intraepithelial lymphocytes that are commonly enriched in TCRγδ+ cells. Recent studies have demonstrated that γδ cells protect the host against chemically induced cutaneous malignancy, but the role of αβ T cells has been enigmatic, with both protective and tumor-enhancing contributions being reported in different systems. This study aims to clarify the contributions of each T cell type to the regulation of squamous cell carcinoma induced in FVB mice by a two-stage regimen of 7,12-dimethylbenz[a]anthracene initiation followed by repetitive application of the tumor promoter 12-O-tetradecanoylphorbol 13-acetate. This protocol permits one to monitor the induction of papillomas and the progression of those papillomas to carcinomas. The results show that whereas γδ cells are strongly protective, the nonredundant contributions of αβ T cells to the host's protection against papillomas are more modest. Furthermore, at both high and low doses of carcinogens, αβ T cells can contribute to rather than inhibit the progression of papillomas to carcinomas. As is likely to be the case in humans, this study also shows that the contribution of T cells to tumor immunosurveillance is regulated by modifier genes