Functional analysis of Ia antigen-bearing keratinocytes: mixed skin lymphocyte culture between Ia antigen-bearing Pam 212 cells and allogeneic and syngeneic splenic T cells

Interleukins 18 and 12 synergistically upregulate interferon-gamma production by murine dendritic epidermal T cells

A unique subset of gammadelta T cells, termed dendritic epidermal T cells, reside in murine epidermis. It was previously reported that freshly isolated dendritic epidermal T cells and dendritic epidermal T cell lines expressed mRNA for interferon-gamma. Recent studies indicated that interleukin-18, a novel cytokine which strongly induces interferon-gamma production by T cells, was produced by murine keratinocytes and Langerhans cells. Interleukin-12, which is regarded as a key cytokine for Th1 type helper clone responses, has also been reported to be produced by these cells in murine skin. In this study, we demonstrated by enzyme-linked immunosorbent assay that interleukin-18 and interleukin-12 synergistically upregulated interferon-gamma production by dendritic epidermal T cells in short-term cultures. This was the case in both C57/BL6 mice and BALB/C mice, although the quantity of interferon-gamma produced was different in the two mouse strains. Interleukin-18 or interleukin-12 alone did not induce interferon-gamma production by dendritic epidermal T cells. Interferon-gamma mRNA was only weakly detected by the semiquantitative reverse transcriptase-polymerase chain reaction method in freshly isolated dendritic epidermal T cells, and the mRNA expression was much increased 12 h after stimulation with interleukin-18 and interleukin-12. We also confirmed biologic activity of interferon-gamma produced by dendritic epidermal T cells by showing upregulation of major histocompatibility complex class II expression on Pam 212, murine keratinocyte cell line. Thus, this study suggests that interleukin-18 and interleukin-12 produced by keratinocytes and Langerhans cells regulate interferon-gamma production by dendritic epidermal T cells and thus may play important parts in the regulation of immune responses in skin-associated lymphoid tissues.

Histoanalytical study of the cellular infiltrate in the tuberculin reaction

In contrast to the generally held view, in previous studies it has been found that the histopathological changes in delayed-type hypersensitivity reactions to intradermal purified protein derivative of tuberculin (PPD) in humans were not uniform. These were classified into three types based on their resemblance to features seen in other dermatoses, i.e.: (i) perivascular dermatitis type; (ii) basal spongiotic dermatitis type; and (iii) erythema multiforme type. These histopathological patterns correlated well with the clinical response seen in tuberculin hypersensitivity of tested subjects. In the present study, the immunohistopathological features in 44 skin biopsy specimens were assessed quantitatively by using multivariate analysis. The numbers of infiltrating cells in the epidermis and in the dermis which were immunohistologically positive to monoclonal antibodies against various mononuclear cells were counted separately to determine if there was any statistical correlation between the histopathological patterns and the phenotypes of infiltrating cells. As a result, a significant correlation was found between the histopathological patterns and the phenotypes of cells infiltrating the epidermis, such as CD8+ cells, CD4+ cells, CD11c+ cells and interleukin 2 receptor positive cells. All these cells showed a high correlation coefficient to the expression of HLA-DR antigen by keratinocytes. Next, factors that might regulate the inflammation and interaction among the infiltrating cells were assessed.(ABSTRACT TRUNCATED AT 250 WORDS)

1 alpha,25-dihydroxyvitamin D3 modulates Ia antigen expression induced by interferon-gamma and prostaglandin E2 production in Pam 212 cells

Recent investigations suggest that 1 alpha,25-dihydroxyvitamin D3 [1 alpha,25(OH)2D3] has an effect on the regulation of immune responses and that keratinocyte (KC) expression of major histocompatibility complex class II antigens may be involved in immune responses. We investigated the modulation by 1 alpha,25(OH)2D3 of Ia antigen expression induced by interferon-gamma (IFN-gamma) and prostaglandin E2 (PGE2) production in Pam 212 cells. 1 alpha,25(OH)2D3 at 10(-6), 10(-8) or 10(-10) M significantly decreased the levels of IFN-gamma-induced Ia antigen expression in Pam 212 cells. Pam 212 cells produced PGE2 and 1 alpha,25-(OH)2D3 enhanced Pam 212 cell PGE2 production. However, indomethacin (1, 5 and 10 micrograms/ml) did not abrogate the inhibitory effect of 1 alpha,25(OH)2D3 on IFN-gamma induction of Ia antigen expression in Pam 212 cells, indicating that the products of the cyclo-oxygenase pathway do not mediate 1 alpha,25(OH)2D3 inhibition of IFN-gamma induction of Pam 212 cell Ia antigen expression. Our studies suggest that in Pam 212 cells the levels of Ia antigen expression induced by IFN-gamma and PGE2 production are negatively and positively regulated by 1 alpha,25(OH)2D3, respectively, and that 1 alpha,25(OH)2D3 may play a role in the regulation of immune responses.

Immunohistopathologic studies in the development of psoriatic lesion influenced by gamma-interferon and the producing cells

Immunological studies on psoriasis have been done using monoclonal antibodies (MoAbs) to elucidate the relation between gamma-interferon (IFN-gamma) secreted from inflammatory infiltrate, and the expression of HLA-DR molecule on epidermal keratinocytes in the lesion. In highly inflamed psoriatic lesions, IFN-gamma producing cells were found in the inflammatory infiltrate of the dermal papillae, while keratinocytes located near IFN-gamma+ cells expressed HLA-DR molecules on the surface. In fully developed psoriatic lesions, HLA-DR+ keratinocytes were mainly found in the thin epidermis over the elongated dermal papillae where IFN-gamma deposited not only at infiltrates but also in teh dermal components. The IFN-gamma+ cells were activated T cells which exhibited HLA-DR and interleukin 2 receptor. Munro's microabscess under the horny layer also included IFN-gamma producing cells. A radioimmunoassay by the sandwich method with anti-human IFN-gamma and anti-recombinant IFN-gamma MoAbs found that extracts from psoriatic scales contained IFN-gamma. The results suggest that HLA-DR+ keratinocytes are due to the effect of IFN-gamma secreted by activated T cells in psoriatic lesions. The proliferation of keratinocytes over the dermal papillae in fully developed lesions seemed to be inhibited by IFN-gamma from the inflammatory infiltrate. We consider that cell-mediated immune reaction plays an important role in the development of psoriatic eruption.

Interferon gamma is a marker for histiocytosis X cells in the skin

In histiocytosis X (HX), which is regarded as a proliferative disease of Langerhans cells (LCs), the tumor cells share characteristic membrane antigens and ultrastructural features with normal LCs. To the present no markers have been described which distinguish HX cells from normal epidermal LCs. Here we report on the selective reactivity of HX cells with a monoclonal antibody against interferon gamma (IFNg). Our results show that HX cells share an epitope with human IFNg while normal LCs do not. It remains to be established whether the expression of IFNg is specific for HX cells or rather characterizes a certain activation state of LCs.

Photoimmunology: the mechanisms involved in immune modulation by UV radiation

Ultraviolet radiation (UVR) may be the most prevalent agent that man encounters in his environment. As a result, certain biological adaptations take advantage of the beneficial effects of UVR exposure, e.g. the photoactivation steps involved in vitamin D metabolism. In this regard, UVR plays an important role in maintaining our good health; however, it must be noted that UVR is potentially the most harmful naturally occurring agent in our environment. Thus, it appears that several mechanisms have evolved to protect us against the detrimental effects of UVR overexposure. Although epidermal melaninization or "tanning" may be the most obvious example of these processes, we would argue that adoptive mechanisms within the immune system also provide protection against UVR-induced skin damage. It is now known that UVR affects the distribution and functional activities of various immunocompetent cells within the skin, as well as modifying the production of inflammatory and hematopoietically active cytokines. This review will focus on the known mechanisms involved in the immune modulatory effects of UVR and how adoptive immune responses to UVR-induced skin damage contribute to specific pathological processes.