Identification of CD4+, 2H4+ (T8 gamma +) suppressor-inducer cells in normal human epidermis and superficial dermis

Resident lymphocytes in the dermis of the normal dorsolateral thoracic skin of alpacas

BACKGROUND

Small numbers of resident T lymphocytes are present in the dermis of normal skin of humans, cattle and sheep.

HYPOTHESIS/OBJECTIVES

We wanted to determine the prevalence, numbers and immunophenotype of lymphocytes in the dermis of healthy skin from alpacas.

ANIMALS

Skin biopsy specimens were collected from the dorsolateral thorax of 31 alpacas with normal skin.

METHODS

Skin biopsy specimens were evaluated for the prevalence and numbers of CD3+ and CD79a+ lymphocytes.

RESULTS

Resident CD3+ and CD79a+ lymphocytes were found around the superficial and deep dermal blood vessels. The CD3+ lymphocytes were more numerous than CD79a+ lymphocytes. Both CD3+ and CD79a+ lymphocytes were more numerous around superficial dermal blood vessels.

CONCLUSIONS AND CLINICAL IMPORTANCE

Resident CD3+ and CD79a+ lymphocytes are present around superficial and deep dermal blood vessels in normal skin from alpacas; hence, the presence of lymphocytes in these locations without obvious features of inflammation must be interpreted cautiously when evaluating skin biopsy specimens from alpacas with skin disease.

CD3+ and BLA.36+ cells do not occur in the epidermis and adnexal epithelia of normal skin from the dorsolateral trunk of cats

A small population of resident T-lymphocytes is present in the normal epidermis of humans, mice, and rats. However, resident epidermal lymphocytes have not been reported in the normal skin of the cat. Skin-biopsy specimens from the normal skin of the dorsolateral trunk from 30 cats were examined histologically and immunohistochemically for the presence of lymphocytes, CD3+ cells, and BLA.36+ cells in epidermis and adnexal epithelia. All examinations were negative. It appears that lymphocytes occur rarely, if at all, in the epidermis and adnexal epithelial of normal cat skin. Hence, the presence of lymphocytes in these structures should be considered abnormal.

CD3+ and BLA.36+ cells do not occur in the epidermis and adnexal epithelia of normal equine skin

Summary A small population of resident T lymphocytes is present in the healthy human and murine epidermis. However, resident epidermal lymphocytes have not been reported in normal skin of the horse. Skin biopsy specimens from the normal skin of 27 horses were examined histologically and immunohistochemically for the presence of lymphocytes, CD3+ cells and BLA.36+ cells in epidermis and adnexal epithelia. All examinations were negative. It appears that lymphocytes occur rarely, if at all, in the epidermis and adnexal epithelia of normal horse skin. Hence, the presence of lymphocytes in these structures should be considered abnormal.

Heterogeneity within tissue-specific macrophage and dendritic cell populations during cutaneous inflammation in atopic dermatitis

BACKGROUND

Macrophages and dendritic cells may play a role in chronicity of atopic dermatitis (AD); however, so far only limited data are documented on the distribution of these cells in the skin during cutaneous inflammation.

OBJECTIVES

To gain better insight into the presence and distribution of macrophage and dendritic cell (sub)populations in acutely and chronically inflamed skin of AD patients.

METHODS

Chronic inflammatory reactions were studied in lesional AD skin biopsies; the atopy patch test was used as a model for the initiation of AD lesions, representing acute inflammation. To determine the number and phenotype of different dermal macrophage and dendritic cell populations immunohistochemistry and digital imaging were used.

RESULTS

There was an increase in macrophage numbers in acutely and chronically inflamed AD skin, whereas absolute dendritic cell numbers were unchanged, compared with non-lesional AD skin. Furthermore, phenotypically heterogeneous and overlapping macrophage and dendritic cell populations were present in inflamed AD skin. The classic macrophage marker CD68 and prototypic dendritic cell marker CD1a could bind to the same cell subpopulation in the dermis of inflamed AD skin. Mannose receptors were expressed mainly by macrophages in inflamed AD skin.

CONCLUSIONS

In this study we observed changes in macrophage number and phenotype during cutaneous inflammation in AD. Dendritic cell numbers did not change; however, phenotypically dendritic cell and macrophage subpopulations showed increasing overlap during inflammation in AD skin. We show for the first time that within tissue-specific macrophage populations further subpopulations are present, and that monocyte-derived cells may express markers for both dendritic cells and macrophages. Our results point to the existence of a heterogeneous pool of macrophage/dendritic cell-like cells, from which subpopulations of dermal macrophages and dendritic cells arise.

Immunohistochemical analysis of late local skin reactions during rush venom immunotherapy

During rush venom immunotherapy (VIT), about 65% of patients develop large local reactions (LLR) at the application site that last for at least 24 h. However, LLR subside during long-term treatment. To learn more about the provenance of infiltrating cells in late, local skin reactions during VIT, we analyzed the skin infiltrates of 23 Hymenoptera venom (HV)-allergic patients. Punch biopsies were obtained 24 h after s.c. injection of HV allergens from 23 HV-allergic patients and five nonallergic controls. Seven patients did not show LLR at the beginning of VIT. Ten patients had LLR when the dose of HV allergens was increased. Six patients showed reduced LLR after long-term treatment. Immunoenzymatic labeling of the cryostal sections with a panel of monoclonal antibodies was performed by the APAAP method. S.c. application of HV allergens induced a perivascular and periadnexial cutaneous mononuclear cell infiltrate consisting mainly of CD4+, CD45RO+; and HLA-DR+ cells in patients without clinically apparent LLR. In contrast, LLR were associated with a significant increase in total cells, CD4+ cells, CD8+ cells, CD11c+ cells, EG2+ cells, NP57+ cells, HLA-DR+ cells, CD45RO+ cells, CD45RA+ cells, CD23+ cells and CD25+ cells (P < 0.001). Decreased LLR after long-term VIT was correlated with a significantly reduced recruitment of CD4+ cells, EG2+ cells, and CD23+ cells as compared to LLR in the course of dose increases (P < 0.05), whereas the number of CD8+ cells, CD11c+ cells, NP57+ cells, and CD25+ cells remained high. Our data suggest that s.c. injections of HV allergens attract CD4+ helper T cells, of both the naive (CD45RA+) and memory (CD45RO+) phenotypes, to the allergen application site. LLR represent delayed allergic rather than toxic reactions to HV components and might be relevant to the development of clinical protection during VIT.

Macrophages, but not Langerhans cell-like cells of dendritic lineage, express the CD36 molecule in normal human dermis: relevance to downregulatory cutaneous immune responses?

The CD36 molecule has been shown to be associated with subsets of peripheral blood monocyte/macrophages and, in cells isolated from either ultraviolet (UV)-irradiated or diseased skin, to induce downregulatory immune responses. Although macrophages are certainly present within normal human dermis, whether they normally express CD36 is still a matter of debate. In this study, we investigated dermal CD36-expressing macrophages in situ using the gold immunoelectron microscopic technique on tissue ultracryosections. This is a very sensitive and specific method, and its results clearly reflect the in vivo immunophenotypic constitutive situation. Macrophages in normal human dermis were variously shaped from round to dendritic and were localized either immediately beneath the epidermis, in perivascular areas, or in intervascular zones. Macrophages showed consistent gold-positive staining on their cell surface. In contrast, other dermal cells, including fibroblasts, lymphocytes, and mast cells, as well as dermal fibers, were not decorated with gold; dermal Langerhans cell-like dendritic cells (LC/DC), though they did show gold labeling in some intracytoplasmic organelles, did not show any gold particles along their plasma membranes. Therefore, although macrophages in normal human dermis exhibit variability with regard to their localization and shape, they regularly and constitutively expressed CD36. CD36 molecules may be considered a useful marker for macrophages in normal human dermis and may furthermore confer on macrophages, or a subpopulation thereof, intriguing functional properties (e.g., downregulatory capacity versus upregulatory capacity subserved by LC/DC) within the cutaneous immune system.

Human epidermal T cells predominantly belong to the lineage expressing alpha/beta T cell receptor

The epidermis of clinically normal-appearing human skin harbors a phenotypically heterogeneous population of T lymphocytes (TCs), the majority of which are CD2+/CD3+/CD5+ "memory" cells, but in an unactivated state, and express the TCR-alpha/beta. In contrast to murine skin, only a very minor subpopulation of CD3+ cells in the human epidermis bears the TCR-gamma/delta. Epidermal TCs primarily are distributed along the rete ridges in the basal keratinocyte layer and are often in close apposition to Langerhans cells (LCs). These TCs were propagated from epidermal cell suspensions after stimulation with TC activating agents (Con A, rIL-1, rIL-2), then evaluated for phenotypic features and TCR diversity. Similar to the in situ situation, most were CD4-/CD8+/TCR-alpha/beta+. In addition, two cultures contained TCR-gamma/delta+ cells; one of these determined to be an adherent CD4-/CD8+ population. Epidermal TCs were significantly (p less than 0.0001) more abundant in the sole than in the other body regions examined (i.e., 40 vs. 7 CD3+ cells/linear centimeter of epidermis) and seemed to have a particular affinity for the acrosyringial epithelium of eccrine sweat ducts. Moreover, the sole usually contained a greater number of CD8+ relative to CD4+ TCs, whereas the epidermal CD4/CD8 ratio in the trunk and extremities was quite variable, although the trend also was towards a slightly larger percentage of CD8+ cells. Collectively, our data suggest that the volar epidermis has a unique microenvironment which is responsible for both the higher density of TCs, preferentially CD8+, and lower number of LCs. This study has not only provided evidence for significant regional variability in the human epidermal TC population of normal skin, but also strengthens the concept for skin-associated lymphoid tissues (SALT), whereby memory TCs recirculate back to the epidermis and interact with resident antigen-presenting cells (i.e., LC).

T-cell inducer populations in cutaneous inflammation: a predominance of T helper-inducer lymphocytes (THi) in the infiltrate of inflammatory dermatoses

The mononuclear infiltrate found in a variety of inflammatory dermatoses was characterized by a predominance of T helper-inducer lymphocytes (THi), CD4+/CD45RA-/CD45RO+, a population of cells responsible for maintaining and promoting immune reactions. Only small numbers of T-suppressor-inducer lymphocytes (TSi), CD4+/CD45RA+/CD45RO-, cells responsible for inducing CD8 suppressor-effector cells to 'down regulate' immune reactions, were seen. The predominance of CD4+ THi lymphocytes was common to all dermatoses studied and suggests a common final pathway in chronic cutaneous inflammation, irrespective of initial causative factors.

Annular erythema associated with primary Sjögren syndrome: analysis of T cell subsets in cutaneous infiltrates

Immunohistochemical analysis was performed on the annular erythema associated with Sjögren syndrome. This type of annular erythema is characterized by a doughnutlike appearance with an elevated border and central pallor; it is distinct from subacute cutaneous lupus erythematosus. Histologically this erythema is characterized by coat sleeve-like infiltration of lymphocytes around blood vessels and by nuclear debris in the connective tissue. Vasculitis or epidermal changes suggestive of lupus erythematosus were not observed in any of the cases, although immunoglobulin or complement deposition along the basement membrane zone and focal liquefaction degeneration of the basal layer in involved skin were seen in some cases. Major dermal infiltrates consisted primarily of CD4+ and 4B4+ lymphocytes.

Human epidermal basal keratinocytes express CDw29 antigens

Two monoclonal antibodies, K20 and 4B4, assigned to the CDw29 cluster of differentiation antigens, were shown to react with basal keratinocytes (BK). The aim of this study was to identify the antigens recognized by K20 and 4B4 on epidermal cells, and to determine whether they were identical to those found on lymphocytes. Basal keratinocyte-enriched cell suspensions were labelled with 125I and then 1% NP40 cell lysates were used for immunoprecipitation. Under reducing conditions, K20 and 4B4 immunoprecipitated from basal keratinocytes a broad MW 105,000 band and proteins of MW 145,000, 90,000 and 80,000. Under non-reducing conditions, each band was shifted down by approximately 5000 MW. Metabolic labelling studies demonstrated that the MW 145,000 and 105,000 subunits were synthesized by basal keratinocytes. On lymphoid cells, K20 and 4B4 are known to precipitate glycoprotein complexes made of a broad MW 130,000 protein band (beta subunit) associated with a protein of MW 150,000 (alpha subunit) and proteins of MW 90,000 and 80,000 expressed in very low amounts. The MW 145,000 and 105,000 bands immunoprecipitated by K20 from basal keratinocytes correspond to the alpha and beta subunits present on lymphoid cells. It has recently been demonstrated that K20 recognizes the common beta subunit of the very late antigens family (VLA) and that 4B4 defines the helper-inducer subset of T lymphocytes. The present investigation provides evidence that basal keratinocytes share antigens of the VLA family with lymphoid cells and that they play an important role in the immune response in the skin-immune system.

Expression of CDw29 and CD45R antigens on epithelial cells in oral lichen planus

The CD45R and CDw29 antigens are expressed on naive and primed helper T cell populations which serve suppressor-inducer or helper-inducer functions, respectively. These antigens may also be expressed on epithelial cell subpopulations. In the present study, monoclonal antibodies reacting with T lymphocytes and Langerhans cells (LC) were used to characterize the expression of CD45R and CDw29 antigens in oral lichen planus. CDw29 was expressed by LC and lymphocytic cells whereas keratinocyte reactivity varied from negative through to full thickness staining. Expression of CD45R was confined to intraepithelial cells with either lymphocytic or dendritic morphology. A relatively constant ratio of CD1a + LC to CD45R + cells (2:1) was seen. These results demonstrate the existence of intraepithelial cells expressing antigens which are functionally important in T cell responses and which may provide local immunoregulatory influences.