Immunohistochemistry of cutaneous graft-versus-host disease after allogeneic bone marrow transplantation

Graft-versus-host disease (GVHD) is an immunologically mediated disease occurring most frequently after allogeneic bone marrow transplantation. The aim of this study was to evaluate the contribution of immunohistochemistry in the diagnosis of cutaneous GVHD. Patients transplanted for either leukemia or beta-thalassemia were included in the study. Skin lesions of acute and chronic GVHD were examined both by direct immunofluorescence to detect immunoglobulin deposits and by an avidin-biotin-peroxidase complex technique to evaluate the inflammatory cell infiltrate. Epidermal and dermal fluorescent bodies (IgG and IgM) were frequently found in both acute and chronic GVHD. Most of the infiltrating cells were CD3+ T lymphocytes, with CD8+ cells representing the major cell population invading the epidermis both in acute GVHD and in chronic lichenoid GVHD. A small proportion of the dermal cells were CD14+ macrophages; no B cells were detected. HLA-DR, but not HLA-DQ antigens, were variably expressed by keratinocytes in all cases of acute GVHD and in chronic lichenoid GVHD. KL-1, a monoclonal antikeratin antibody specific for the 56.5 KD acidic polypeptide usually present in suprabasal keratinocytes, stained all epidermal layers, including the basal layer. Langerhans cells were dramatically reduced in number in the epidermis of both acute and chronic lichenoid GVHD. It is concluded that immunohistologic analysis may be supportive in the diagnosis of acute and early chronic lichenoid cutaneous GVHD.     

Comparison of the distribution and numbers of antigen-presenting cells among T-lymphocyte-mediated dermatoses: CD1a+, factor XIIIa+, and CD68+ cells in eczematous dermatitis,psoriasis, lichen planus and graft-versus-host disease

Antigen-presenting cells (APCs) participate in the initiation of the inflammatory process in various immune-mediated dermatoses through the activation of antigen-specific T lymphocytes. The skin contains several different subsets of APCs. To investigate the role of these APCs in T-cell immune-mediated inflammation, we examined the distribution and numbers of epidermal and dermal CD1a(+) dendritic cells (DCs), factor XIIIa(+) dermal DCs, and CD68(+) macrophages in five T-cell-mediated inflammatory skin diseases. Immunohistochemistry of CD1a, factor XIIIa, and CD68 was performed using paraffin-embedded tissue obtained from a total of 51 patients with eczematous dermatitis (histologically spongiotic dermatitis), psoriasis, lichen planus, acute graft-versus-host disease (GVHD), and chronic GVHD. The numbers of positive cells for each staining were compared with those in site-matched normal skin control specimens from aged-matched subjects. In spongiotic dermatitis and lichen planus, the numbers of epidermal and dermal CD1a(+) cells and factor XIIIa(+) cells were significantly greater than in normal control skin, while in psoriasis only factor XIIIa(+) cells were significantly increased in number. Acute and chronic GVHD showed a reduced number of dermal CD1a(+) cells. Interestingly, factor XIIIa(+) cells were decreased in acute GVHD while they were increased in chronic GVHD. There was a significant reduction in epidermal CD1a(+) cells in acute GVHD, but not in chronic GVHD. The differences in the numbers of APCs in lesional skin appeared to reflect differences in the pathophysiology of these inflammatory skin diseases.     

Skin CD4+ T cells produce interferon-gamma in vitro in response to streptococcal antigens in chronic plaque psoriasis

Recently, we have demonstrated that group A streptococcal antigen reactive T cells are present in the skin lesions of chronic plaque psoriasis. To determine the cytokine profile (interferon-gamma, interleukin-4 and interleukin-10) of these T cells in response to streptococcal antigens, T cell lines were cultured from untreated lesional skin of 13 patients with chronic plaque psoriasis and 12 patients with other inflammatory skin diseases. T cell lines were incubated with or without a sonicated heat-killed mixture of group A streptococcal isolates for 18 h in the presence of a transport inhibitor, stained for surface CD4 or CD8 and intracellular cytokine expression, and analyzed by flow cytometry. Psoriatic T cell lines were grown from 10 of 13 patients and were predominately CD4+ (64%-85%) with 10%-32% CD8+ T cells. Variable numbers of CD4+ T cells produced interferon-gamma (0.8%-35%, median 13.9) in eight of 10 T cell lines (p < 0.02). In contrast, CD4+ T cells in five of 12 T cell lines obtained from disease controls did not produce or produced minimal interferon-gamma in response to group A streptococcal isolates; this was significantly different from the psoriatic T cell lines (p < 0.05). Small numbers of interleukin-10 positive (0.8%-1.3%) and interleukin-4 positive (2.1%-2.5%) CD4+ T cells induced by group A streptococcal isolates were also present in two out of five and three out of five psoriatic T cell lines, respectively. This was significantly less in each case than the numbers of CD4+/interferon-gamma+ T cells (p < 0.05). Cytokine-positive CD8+ T cells were rarely observed. These findings demonstrate that a subpopulation of CD4+ T cells in chronic plaque psoriasis skin lesions produces interferon-gamma in response to streptococcal antigens and may be relevant to the pathogenesis of psoriasis.     

Immunohistochemical Study of Graft-versus-Host Reaction (GVHR)-Type Drug Eruptions

Skin biopsies of graft-versus-host reaction (GVHR)-type drug eruptions in the acute phase were compared immunohistochemically with those in the chronic phase and also with non-GVHR type drug eruptions in the acute phase. Predominance of CD8⁺ T cells in the epidermal infiltrates, reduction in the number of epidermal OKT6⁺ dendritic cells (Langerhans cells), and increased expression of HLA-DR and ICAM-1 on keratinocytes were observed in the acute phase of GVHR-type, but not in either the chronic phase of GVHR-type or the acute non-GVHR type. These findings were similar to those of previous reports on skin lesions of acute GVH disease (GVHD) seen after bone marrow transplantation. Therefore, immunohistochemistry is not useful for differential diagnosis between acute GVHR-type drug eruptions and acute cutaneous GVHD. These findings also indicate that similar immunomechanisms may be involved in the pathogenesis of both GVHR-type drug eruptions and cutaneous GVHD.     

Distribution of natural killer cells and lymphocyte subclasses in Jessner's lymphocytic infiltration of the skin and in cutaneous lesions of discoid and systemic lupus erythematosus

We studied the cell infiltrates in biopsies from lymphocytic infiltration of the skin (LIS), with six monoclonal T cell antigen-specific antibodies and compared the reactivity pattern with those in biopsies from discoid and systemic lupus erythematosus skin lesions and allergic contact skin reactions. A newly described antibody (NK₉) recognizing natural killer (NK) cells and activated cytotoxic T lymphocytes was included, and the numbers and activity of circulating NK cells was determined. Immunohistochemical staining revealed that the numbers of NK₉-positive cells were highest in LIS. The distribution of T lymphocytes (OKTii + ve), helper T cells (OKT₄+ ve), suppressor T celts (OKT8 + ve), Langerhans cells (OKT6 + ve) and activated T cells (anti-Tac + ve) in LIS differed from those in DLE, SLE and allergic contact reactions. However, the number of circulating NK cells (large granular lymphocytes) and the NK activity in peripheral blood were normal in LIS. We conclude that in LIS a distinct type of T cell activation occurs; the cause of this remains to be determined.     

Immunoregulation of allergic contact dermatitis

Allergic contact dermatitis (ACD) to haptens can serve as a valuable paradigm for understanding the physiopathology of T cell mediated immune responses. In sensitized individuals, exposure to the relevant hapten initiates clinical expression of ACD, which depends on the rapid activation of specific T cells. Mechanisms of tissue damage include direct cytotoxicity against keratinocytes, mostly mediated by CD8+ T cells, and T cell release of cytokines, which amplify the inflammatory response by targeting resident skin cells. The expression of ACD is actively regulated by specialized subsets of T lymphocytes with suppressive functions. In particular, T regulatory cells producing high levels of IL-10 suppress ACD by blocking the functions of dendritic cells. In contrast CD4+CD25+ regulatory T cells prevent immunopathological reactions and maintain peripheral tolerance to haptens by acting via a cell-to-cell contact mechanism. Understanding the role of suppressor T cells and the requirements for their in vivo and in vitro expansion are critical steps for the development of specific desensitization protocols in hapten-allergic individuals. This information may also provide the basis for novel interventions in other immune-mediated diseases.     

Development and characterization of a monoclonal antibody specific for fucosyltransferase VII (Fuc-TVII): discordant expression of CLA and Fuc-TVII in peripheral CD4+ and CD8+ T cells

Although cutaneous lymphocyte-associated antigen (CLA) is thought to be specifically expressed on skin "homing" T cells, it has become clear that CLA is not directly involved in binding to E-selectin but represents an excellent marker for high levels of fucosyltransferase VII (Fuc-TVII): Fuc-TVII can regulate the ability of T cells to migrate into the skin by generating a binding site for E-selectin. In this study, by using a novel monoclonal antibody for Fuc-TVII, we investigated whether expression of Fuc-TVII could be selectively detected in various CLA+ cell lines and peripheral blood T cells. Fuc-TVII was readily detected in the cytoplasm, but not in the membrane, of CLA+ cell lines. Cytoplasmic Fuc-TVII expression was also detectable in both CD4+ and CD8+ T cells purified from peripheral blood mononuclear cells. Nevertheless, there were significant numbers of CLA-expressing CD4+ or CD8+ T cells that did not coexpress Fuc-TVII, and vice versa: either the CD4+ or the CD8+ T cell population consisted of a variable ratio of CLA+ Fuc-TVII+, CLA+ Fuc-TVII-, and CLA- Fuc-TVII+ cells; and CLA+ Fuc-TVII- cells were the most abundantly identifiable phenotype in peripheral blood CD4+ and CD8+ T cells. Thus, according to their expression pattern, skin "homing" T cells can be subdivided into at least three populations, CLA+ Fuc-TVII+, CLA+ Fuc-TVII-, and CLA- Fuc-TVII+ cells. Our study provides convincing evidence that skin "homing" T cells are phenotypically heterogenous and that Fuc-TVII expression, in combination with CLA expression, is a useful phenotypic marker for identifying skin "homing" T cells in mixed cell populations.     

Depletion of CD4+ cells exacerbates the cutaneous response to acute and chronic UVB exposure

Solid organ transplant recipients have a 60-250-fold increased likelihood of developing sunlight-induced squamous cell carcinoma (SCC) compared with the general population. This increased risk is linked to the immunosuppressive drugs taken by these patients to modulate T cell function, thus preventing organ rejection. To determine the importance of T cells in the development of cutaneous SCC, we examined the effects of selectively depleting Skh-1 mice of systemic CD4+ or CD8+ T cells, using monoclonal antibodies, on ultraviolet B (UVB) radiation-induced inflammation and tumor development. Decreases in systemic CD4+ but not CD8+ T cells significantly increased and prolonged the acute UVB-induced cutaneous inflammatory response, as measured by neutrophil influx, myeloperoxidase activity, and prostaglandin E2 levels. Significantly more p53+ keratinocytes were observed in UVB-exposed CD4-depleted than in CD4-replete mice, and this difference was abrogated in mice depleted of neutrophils before UVB exposure. Increased acute inflammation was associated with significantly increased tumor numbers in CD4-depleted mice chronically exposed to UVB. Furthermore, topical treatment with the anti-inflammatory drug celecoxib significantly decreased tumor numbers in both CD4-replete and CD4-depleted mice. Our findings suggest that CD4+ T cells play an important role in modulating both the acute inflammatory and the chronic carcinogenic response of the skin to UVB.     

Proliferative activity of CD8(+) T cells as an important clue to analyze T cell-mediated inflammatory dermatoses

Abstract To elucidate the pathogenesis of T cell-mediated inflammatory skin diseases, we examined the exact sites where CD8(+) T cells proliferate, correlating them with the localization of antigen-presenting dendritic cells. We performed CD8/Ki-67 double immunohistochemical staining and single staining for CD1a, CD68, and factor XIIIa on sections of paraffin-embedded tissue samples of inflammatory dermatoses in which T lymphocytes are thought to play a crucial role. The dermatoses were lichen planus (12 samples), acute graft-versus host disease (GVHD) (12 samples), chronic GVHD (10 samples), spongiotic dermatitis (8 samples) and psoriasis (7 samples). Labelling for Ki-67 among CD8(+) T cells was predominantly observed in the subepidermal lymphoid infiltrate, and was scanty in the epidermis. This suggested that proliferation of CD8(+) T cells occurred preferentially in the dermis. The labelling index for Ki-67 among dermal and epidermal CD8(+) cells was quite different among the different diseases studied (P < 0.05). They were rich in the subepidermal portion of the dermis of spongiotic dermatitis, acute GVHD and chronic GVHD, but rare in the dermis of psoriasis and lichen planus. A moderate infiltrate was also observed in lesional epidermis of spongiotic dermatitis, acute GVHD and chronic GVHD, whereas they was almost none in the epidermis of psoriasis and lichen planus. CD1a(+) dermal dendritic cells were densely distributed within the lymphoid infiltrate in the affected dermis of spongiotic dermatitis, psoriasis and lichen planus, whereas they were minimal in GVHD. These dermal dendritic cells are candidates as stimulators on T cells in the dermis. In conclusion, the proliferative status of T cells could be an important clue in the elucidation of the pathophysiology of T cell-mediated inflammatory dermatoses. Received: 13 December 2000 / Revised: 24 April 2001 / Accepted: 11 July 2001     

The HECA-452 epitope is highly expressed on lymph cells derived from human skin

The cutaneous lymphocyte-associated antigen (CLA), recognized by the monoclonal antibody HECA-452, is a cell surface glycoprotein that binds specifically to E-selectin. CLA is present on most T cells at sites of cutaneous immune response and has been shown to be important in lymphocyte homing to the skin. It is expressed only by a minor subset of peripheral T cells and is absent on thymocytes. We have analysed (using a FACScan flow cytometer) the expression of CLA on human lymph cells derived from normal skin, from ultraviolet (UV)-irradiated skin and from allergic contact dermatitis. Whereas in the peripheral blood CLA was expressed on < 20% of CD4 +, CD8 + and CD56 + cells (natural killer cells), > 60% of CD4 +, CD8 + and CD56 + cells isolated from skin-derived lymph expressed CLA. Furthermore, > 90% of CD1a + dendritic lymph cells were positive for CLA. UV irradiation of the skin and induction of an allergic contact dermatitis did not change CLA expression on lymph cells, although lymph flow and cell output increased. These results provide further evidence for an important role of CLA in cell homing to the skin.     

Cellular and molecular pathophysiology of cutaneous drug reactions

Hypersensitivity reactions to drugs can cause a variety of skin diseases like maculopapular, bullous and pustular eruptions. In recent years increasing evidence indicates the important role of T cells in these drug-induced skin diseases. Analysis of such drug-specific T cell clones has revealed that drugs can be recognized by alpha beta-T cell receptors, not only if bound covalently to peptides, but also if the drug binds in a rather labile way to the presenting major histocompatibility complex (MHC)-peptide. This presentation is sufficient to stimulate T cells. In maculopapular exanthema (MPE), histopathological analysis typically shows a dominant T cell infiltration together with a vacuolar interface dermatitis. Immunohistochemical studies demonstrate the presence of cytotoxic CD4+ and to a lesser degree of CD8+ T cells, which contain perforin and granzyme B. They are close to keratinocytes that show signs of cell destruction. Expression of Fas ligand is barely detectable, suggesting that cytotoxic granule exocytosis may be the dominant pathway leading to keratinocyte cell damage. While in MPE, the killing of cells seems to be predominantly mediated by CD4+ T cells, patients with bullous skin disease show a strong CD8+ T cell migration to the epidermis. This is probably due to a preferential presentation of the drug by MHC class I molecules, and a more extensive killing of cells that present drugs on MHC class I molecules. This might lead to bullous skin diseases. In addition to the presence of cytotoxic T cells, drug-specific T cells also orchestrate the inflammatory skin reaction through the release and induction of various cytokines [i.e. interleukin (IL)-5, IL-6, tumor necrosis factor-alpha and interferon-gamma] and chemokines (RANTES, eotaxin or IL-8). The increased expression of these mediators seems to contribute to the generation of tissue and blood eosinophilia, a hallmark of many drug-induced allergic reactions. However, in acute generalized exanthematous pustulosis (a peculiar form of drug allergy), neutrophils represent the predominant cell type within pustules, probably due to their recruitment by IL-8 secreting drug specific T cells and keratinocytes.     

The role of cutaneous dendritic cells in the immunopathogenesis of atopic dermatitis

We review the immunology of atopic dermatitis (AD) and focus attention on the role of cutaneous dendritic cells. AD is a complex immune-mediated skin disorder characterized by the recruitment of both CD4+ and CD8+ T cells into the skin. T-helper (Th) 2-type cytokines are dominant in acute AD skin, while both Th1- and Th2-type cytokines are present in chronic AD. Cutaneous dendritic cells, which are present in increased numbers within AD skin, are believed to play a key part in the activation of T cells in the skin. They may also help to determine the pattern of cytokines produced by activated effector T cells.     

Absence of cutaneous TNFalpha-producing CD4+ T cells and TNFalpha may allow for fibrosis rather than epithelial cytotoxicity in murine sclerodermatous graft-versus-host disease, a model for human scleroderma

Graft-versus-host disease (GVHD) is a complication of hematopoietic cell transplantation and is a major source of morbidity and mortality. Two main forms of GVHD occur: cytotoxic GVHD (Cyt GVHD), in which TNFalpha is a critical cytokine in epithelial injury, and sclerodermatous GVHD (Scl GVHD), in which TGFbeta plays a major role in fibrosis. To understand the critical early events in GVHD and scleroderma, we are studying a murine model that uses differences in minor histocompatibility antigens to generate Scl GVHD. We asked the question: what is the immune environment in this model that promotes fibrosis rather than the epithelial injury of Cyt GVHD? We found that in Scl GVHD, cutaneous CD4+ T cells produced IFNgamma and IL-2 but not TNFalpha, also absent by gene array analysis. The role of cutaneous CD4+ T cells in Scl GVHD may not be an active process through production of TGFbeta, but may rather be a passive one due to lack of antigen-presenting cell (APC) support for CD4+ T cells and failure to produce TNFalpha, a potent inhibitor of TGFbeta-induced fibrosis as well as inducer of keratinocyte apoptosis. These APC-T cell interactions and the cytokine environment promote fibrosis rather than cytotoxic epithelial injury in skin in Scl GVHD.     

Antigen presenting cells and T lymphocytes in the induction phase of contact hypersensitivity

When a sensitizing substance that induces contact hypersensitivity, fluorescein isothiocyanate (FITC), was painted on abdominal skin of mice, FITC+ cells appeared in the inguinal lymph node after 24 hours. The FITC+ cell in the lymph node was relatively large in size, and it did not appear to be a T lymphocyte. When FITC was painted on either murine tail skin or skin pre-treated by tape stripping, the number of FITC+ cells in the inguinal lymph node was significantly less than that in the positive control. In the mesenteric lymph nodes, which have a different lymph flow from that of the skin regional lymph node, FITC+ cells did not increase in number, and the few FITC+ cells were not significantly different in number among above-mentioned experimental systems. In the inguinal lymph nodes on the 4th day after painting of picryl chloride (PCl) on the abdominal skin of mice, L3T4+ cells, which expressed an interleukin 2 receptor (IL-2R), increased in number. On the other hand, when PCl was painted on either tail skin or skin treated by tape stripping, L3T4+ IL-2R+ cells did not increase in the skin regional lymph nodes. The number of L3T4+ IL-2R+ cells in the mesenteric lymph nodes did not increase in any of the experimental systems mentioned above. These results suggest some relationship between antigen presenting cells and T lymphocytes, as well as one between the skin and the regional lymph nodes, in an induction phase of sensitization in contact hypersensitivity.     

Transfusion-associated graft-versus-host disease: an in situ hybridization analysis of the infiltrating donor-derived cells in the cutaneous lesion.

BACKGROUND: Acute graft-versus-host disease (GVHD) can occur after a blood transfusion. OBJECTIVE: In order to elucidate the pathomechanisms responsible for transfusion-associated GVHD, infiltrating donor-derived cells in a cutaneous lesion were analyzed. METHODS: A skin sample obtained from a 69-year-old woman who developed fatal GVHD after blood transfusions from male donors was studied by performing in situ hybridization (ISH) with a Y-chromosome-specific probe. RESULTS: The cell infiltrates comprised mainly CD3+ T lymphocytes. Immunohistochemistry and ISH in combination demonstrated that 99% (182/184) of the Y-body-positive cells were CD3+. Y bodies were observed in 80% of the CD8+ cells in the epidermis and dermoepidermal junction and in 77 and 45% of the CD8+ and CD4+ cells, respectively, in the dermis. CONCLUSION: These findings suggest that both CD4+ and CD8+ cells of donor origin were involved in the development of cutaneous GVHD.     

Peptide immunization indicates that CD8+ T cells are the dominant effector cells in trinitrophenyl-specific contact hypersensitivity

The identity of the effector T cell population involved in contact hypersensitivity is still questionable with evidence promoting both CD4+ or CD8+ T cells. Previous experimental studies have relied on the in vivo depletion of T cell subsets using antibody, or the use of knock-out mice with deficiencies in either CD4+ or CD8+ T cell-mediated immunity. To address the role of the class I- and class II-mediated pathways of T cell activation in contact hypersensitivity responses in mice with an intact immune system, we utilized various trinitrophenyl-derivatized peptides, which bind specifically with H-2Kb (major histocompatibility complex class I) or H-2I-Ab (major histocompatibility complex class II). The subcutaneous injection of major histocompatibility complex class II-specific, but not of class I-binding, hapten-derivatized peptides in incomplete Freund's adjuvant induced specific, albeit low, contact hypersensitivity responsiveness to trinitrochlorobenzene. When bone-marrow-derived dendritic cells, however, were pulsed with the same peptides and administered intradermally, the opposite result was observed, namely that the class I binding peptides induced contact hypersensitivity responses similar to that observed after epicutaneous trinitrochlorobenzene application. In contrast, dendritic cells pulsed with major histocompatibility complex class II binding peptides did not reproducibly sensitize for contact hypersensitivity responses. Surprisingly, both immunization protocols efficiently induced CD8+ effector T cells. These results support the notion that CD8+ T cells are the dominant effector population mediating contact hypersensitivity responsiveness and that the CD4+ T cell subset only contributes little if at all.     

MHC class II-KO mice are resistant to the immunosuppressive effects of UV light.

Ultraviolet B light is responsible for the development of skin cancer through inhibition of cellular immune responses in the skin. Here, we addressed the question of the mechanisms involved in UVB-induced immune suppression. We used a model of antigen-specific skin inflammation, the contact hypersensitivity (CHS) reaction to DNFB, which is mediated by CD8+ effector T cells and down-regulated by CD4+ T cells. We show that UVB have opposite effects on CD4+ and CD8+ T cells. UVB irradiation reduced the number of activated CD8+ T cells in the lymphoid organs and impaired their functional activity. This resulted in deficient infiltration of IFN-gamma producing CD8+ T cells at challenged site and consequently in the inability to develop an antigen-specific CHS reaction. This effect is mediated by CD4+ suppressor cells, since in the absence of CD4+ T cells (MHC class II-KO mice and CD4+ T cell-depleted mice), UVB have no immunosuppressive effects. Indeed, UVB-irradiated CD4+ T cell-deficient mice have a normal frequency of IFN-gamma-producing hapten-specific CD8+ T cells in the lymphoid organs and develop a normal CHS reaction to DNFB. Thus, in the absence of CD4+ T cells, UVB do not alter the priming of MHC class I-restricted CD8+ effector T cells. Collectively, these data show that UVB-induced immune suppression is secondary to preferential activation of CD4+ suppressor T cells and not to deficient priming and expansion of the effector CD8+ T cell population. This may have important implications for the prevention of UV-induced skin cancers.     

Numbers of murine dermal mast cells remain unchanged during chronic ultraviolet B irradiation

Dermal mast cell numbers reportedly increase in response to chronic ultraviolet irradiation in both humans and in the HRS/Skh-1 mouse model of human photoaging. It has been hypothesized that these increased numbers of mast cells are responsible, at least in part, for the damage in this chronically irradiated or photoaged skin. However, few actual quantitative data have been reported to support this claim of increased dermal mast cell numbers caused by chronic ultraviolet irradiation. We sought to quantify the numbers of dermal mast cells in the skin of chronic ultraviolet-irradiated and control HRS/Skh-1 hairless mice. Dermal mast cells from irradiated and age-matched control mice were quantified by digital image analysis during a 20-week period of exposure to ultraviolet B (UVB) radiation. During the entire course of irradiation, there was no difference in the numbers of dermal mast cells between the irradiated and nonirradiated age-matched control mice. Visible physical evidence of the effects of chronic UVB irradiation, i.e., skin wrinkling, was evident after 6 weeks of treatment. The numbers of dermal mast cells in unirradiated age-matched NSA (CF-1) haired mice were three- to four-fold lower than those in either ultraviolet-exposed or unexposed HRS/Skh-1 mice. These findings indicate that dermal mast cell numbers in HRS/Skh-1 mice are not increased by chronic exposure to UVB radiation.     

Identification of natural killer (NK) cells in lesions of human cutaneous graft-versus-host disease: expression of a novel NK-associated surface antigen (Kp43) in mononuclear infiltrates.

We performed an immunohistochemical analysis of skin biopsies from 13 allogeneic bone marrow transplant (BMT) recipients, undergoing either acute graft-versus-host-disease (aGVHD, n = 8) or chronic GVHD (cGVHD, n = 5). A panel of different monoclonal antibodies (MoAb) was employed including anti-CD2, -CD3, -CD4, -CD8, -CD11b, -CD16, -CD56, and -CD57, as well as a recently described reagent (HP-3B1) specific for a novel natural killer (NK)-associated cell-surface antigen (Kp43). Our data indicate that in aGVHD lesions the proportions of CD2+ cells often exceeded those detected with anti-CD3 MoAb. Double labeling confirmed the presence of CD2+ CD3- lymphocytes and suggested the coexpression in some cells of CD2 and CD11b. When MoAb specific for non-lineage-restricted NK-associated markers were employed, anti-CD56 and -CD57 occasionally stained variable numbers of lymphocytes (means = 14.6% of mononuclear cells in 0.05 mm2, range less than 1-48% and means = 10.3%, range 2-25%, respectively), whereas no CD16+ lymphocytes were observed. In contrast, most samples consistently displayed substantial proportions of Kp43+ cells (means = 32.8%, range 12-63%), which appeared CD3- and were mainly located at the dermoepidermal junction. On the other hand, sections from most (four of five) cGVHD lichenoid lesions analyzed displayed lower proportions of Kp43+ and CD56+ cells. Our data point out the interest of the anti-Kp43 MoAb to identify NK cells in aGVHD lesions, suggesting their pathogenetic participation.