Induction of hapten-specific lymphoid cell proliferation by liposome-carrying molecules from haptenated epidermal cells in contact sensitivity

In vitro activation of immune lymph node cell proliferation by photohapten-modified cells in murine contact photosensitivity

Painting of 3,3',4',5-tetrachlorosalicylanilide (TCSA) plus ultraviolet A (UVA) irradiation to the same site induces contact photosensitivity (CPS), but at the same time results in death of the photohapten-modified cells. Using an in vitro immune lymph node cell (LNC) proliferation system, we investigated the mechanism of induction and elicitation of CPS by TCSA painting plus UVA irradiation. The proliferation of LNC from TCSA-photosensitized mice was not augmented by the addition of TCSA-photocoupled syngeneic spleen cells (SC) or epidermal cells (EC), whereas the picryl chloride immune LNC proliferation was activated by trinitrophenyl-coupled (TNP-coupled) SC or EC. While the viability of SC and EC was unchanged even after TNP haptenization, cells showed very low levels of viability after TCSA photohaptenization. This suggests that the inability of photoTCSA-modified cells to activate LNC proliferation is because of their low viability. Nylon wool column purified lymph node T cells from TCSA-photosensitized mice were activated by photohapten-conjugated SC or photohaptenized EC fragments only in the presence of peritoneal macrophages (M phi). The function of live M phi was not replaced by interleukin-1 (IL-1), suggesting that M phi were required for processing and/or presentation of photohapten rather than simply providing IL-1. Our in vitro study implies that photoTCSA-modified cells generated in vivo require intact antigen-presenting cells to effectively induce and elicit the CPS reaction.

Ultrastructural localization of 2,4-dinitrophenyl groups in mouse epidermis following skin painting with 2,4-dinitrofluorobenzene and 2,4-dinitrothiocyanatebenzene: an immunoelectron microscopical study

The ultrastructural localization of 2,4-dinitrophenyl (DNP) groups in mouse epidermis after epicutaneous application of the contact sensitizer 2,4-dinitrofluorobenzene (DNFB) and the tolerogen 2,4-dinitrothiocyanatebenzene (DNTB) was investigated at varying times using immunoelectron microscopy with the protein A - gold technique. After application of DNFB, there was a homogenous cytoplasmic labeling of all epidermal cells. The intracellular localization of the DNP groups was not restricted to cytoplasmic organelles belonging to the endocytotic - lysosomal system. The numerous endocytotic organelles, Birbeck granules, and lysosomes of the Langerhans cells (LCs) typically observed after application of contact sensitizers also did not show an increased number of gold particles. Skin painting with DNTB resulted in a similar distribution and time-course of immunolabeling, but this compound did not induce cellular and the endocytotic activation of LCs as seen after DNFB application. These results demonstrate that contact sensitizers do not require specific cellular uptake and intracellular processing by the endocytotic - lysosomal compartment of the LCs before membrane presentation. However, a cellular and endocytotic activation of the LCs by haptens may be an important mechanism for T effector cell activation.

Ultrastructural cytochemical visualization of chromium in the skin of sensitized guinea pigs

Using a modified sulfide silver method for electron microscopy, the intraepidermal and intracellular localization of epicutaneously applied potassium dichromate was investigated at varying times in sensitized and nonsensitized guinea pigs. The hapten penetrated rapidly into the epidermis. There was a homogeneous extra- and intracellular staining of the keratinocytes in the upper epidermis. The basal and suprabasal cells, by contrast, exhibited a predominant extracellular and plasma membrane localization of the silver grains. This membrane staining pattern was also observed in the Langerhans cells showing cellular and endocytotic activation in the sensitized animals. No specific cellular uptake of the hapten by the Langerhans cells was found. These results demonstrate that the epicutaneous application of chromate resulted in a characteristic intraepidermal distribution which may be related to the epidermal conversion of the hexavalent chromate to the immunogenic trivalent form. Moreover, the absent intracellular localization of the hapten in the activated Langerhans cells supports the notion that contact allergens can be presented to T cells without prior intracellular processing.

Effect of UVB radiation on the biosynthesis of HLA-DR antigens

HLA-DR molecules on the surface of immunocompetent cells are thought to represent target structures for the immunomodulating effects of UV radiation during the induction of an immune response. We therefore investigated the effect of UVB radiation on the de novo synthesis of HLA-DR-gamma-chains in the cytoplasm and the expression of alpha- and beta-chains on the surface of the human lymphoblastoid B-cell line Raji. Raji cells were UVB irradiated before biochemical experiments were performed. Cells were then metabolically labeled or radioiodinated and detergent lysates immunoprecipitated using antibodies directed against the gamma- or the alpha- and beta-chain of the HLA-DR molecule. Over a wide dose range, UVB-irradiated Raji cells were shown to still express HLA-DR determinants on their surface and, even more importantly, to be capable of synthesizing HLA-DR-alpha, beta- and gamma-chains in a normal fashion. Despite this, the functional capacity of Raji cells was impaired in a dose-dependent manner. UV radiation thus seems to exert its immunomodulating effects primarily at a different level than the incriminated immune-response-associated antigens, which are expressed as recognition structures on the surface of immunocompetent cells.

Ia antigen expressed by keratinocytes can be the molecule of antigen presentation in contact sensitivity

Immune response-associated (Ia) antigens are important as molecules in antigen recognition by T cells. Keratinocytes can express Ia antigens in many inflammatory dermatoses and by action of gamma interferon (IFN-gamma). A keratinocyte cell line, Pam 212 cells, expressed Ia antigens at maintaining culture. They also expressed Ia antigens under the influence of IFN-gamma. Liposomes carrying molecules from trinitrophenylated-Pam cells did not stimulate lymphnode cells (LCs) of contact sensitivity; however, liposomes carrying a large amount of those molecules stimulated LCs. This stimulation was attributable to contaminated Ia antigens in those molecules. Liposomes with a small amount of those molecules or trinitrophenylated-proteins from Pam cells were prepared. Into them were inserted Ia antigen-rich proteins from Pam cells, spleen cells, IFN-gamma-treated Pam cells, or epidermal cells containing Langerhans cells. Thus prepared liposomes stimulated the LCs significantly. The Ia antigens obtained from IFN-gamma-treated Pam cells worked as well as Ia antigens from epidermal cells that contained Langerhans cells as the molecule of antigen presentation in contact sensitivity.

Delayed-type skin reaction to 2,4-dinitrophenylated epidermal cells in guinea pigs with contact sensitivity to 2,4-dinitrochlorobenzene

Contact sensitivity (CS) induced by hapten has been thought to be analogous to delayed-type hypersensitivity, such as the Mantoux reaction, because of outstanding similarities between the two phenomena. It can be suggested that animals with CS respond also to intradermal injection of the conjugate of hapten and protein as well as to epicutaneous application of hapten. However, evidence against this has been reported. In the present experiments, delayed-type skin reaction (DSR) was successfully obtained in JY1 strain guinea pigs sensitized by painting the skin with 2,4-dinitrochlorobenzene using in vitro dinitrophenylated epidermal cell suspension (DNP-EC) as antigen for a delayed intradermal test. The experiment using anti-Ia alloantiserum and complement showed that the elicitation of DSR is due to the presence of Ia-positive cells (presumably Langerhans cells) among DNP-ECs. The delayed intradermal test with the conjugates such as haptenated ECs in the animals with CS is considered to be an experimentally useful way of analysing the antigen in the sensitivity.

Induction and suppression of contact sensitivity by liposomes carrying molecules from haptenated epidermal cells

Liposomes carrying molecules from trinitrophenylated epidermal cells (TNP-EC) liposomes stimulated the hapten-specific proliferation of lymphocytes in vitro in our previous study. In order to analyze the role of TNP-EC liposomes in vivo, they were injected into naive mice. TNP-EC liposomes induced contact sensitivity effectively when injected either s.c. or i.p. Contact sensitivity induced by TNP-EC liposomes was a long-lived T cell-mediated reaction. A s.c. injection of liposomes with molecules from TNP-Ia antigen-depleted epidermal cells [TNP-EC (Ia-) liposomes] failed to induce contact sensitivity and developed unresponsiveness. This unresponsiveness was transferred by T cells, i.e., suppressor T cells. Therefore, it is suggested that Ia antigens in epidermal cells play a critical role for induction and suppression of contact sensitivity.