Major histocompatibility complex class I-restricted CD8+ T cells and class II-restricted CD4+ T cells, respectively, mediate and regulate contact sensitivity to dinitrofluorobenzene

Contact sensitivity (CS) is a form of delayed-type hypersensitivity to haptens applied epicutaneously and is thought to be mediated, like classical delayed-type hypersensitivity responses, by CD4+ T helper-1 cells. The aim of this study was to identify the effector T cells involved in CS. We studied CS to the strongly sensitizing hapten dinitrofluorobenzene (DNFB) in mice rendered deficient by homologous recombination in either major histocompatibility complex (MHC) class I, MHC class II, or both, and which exhibited deficiencies in, respectively, CD8+, CD4+, or both, T cells. MHC class I single-deficient and MHC class I/class II double-deficient mice, both of which have a drastic reduction in the number of CD8+ T cells, were unable to mount a CS response to DNFB. In contrast, both MHC class II-deficient mice and normal mice treated with an anti-CD4 monoclonal antibody (mAb) developed exaggerated and persistent responses relative to heterozygous control littermates. Furthermore, anti-CD8 mAb depletion of class II-deficient mice totally abolished their ability to mount an inflammatory response to DNFB. Removal of residual CD4+ T cells in class II-deficient mice by anti-CD4 mAb treatment did not diminish the intensity of CS. These data clearly demonstrate that class I-restricted CD8+ T cells are sufficient for the induction of CS to DNFB, and further support the idea that MHC class II-restricted CD4+ T cells down-regulate this inflammatory response.

Optimization of the mouse ear swelling test for in vivo and in vitro studies of weak contact sensitizers

Murine models for the assessment of the contact sensitizing properties of chemicals rely on mouse ear swelling tests (Mest), which are not sensitive enough to detect weak sensitizers. The aim of the present study was to develop in mice an adjuvant-free Mest appropriate for in vivo detection of any type of sensitizer (weak to strong), and useful for in vitro assessment of contact sensitivity (CS). 3 haptens were tested: dinitrochlorobenzene (DNCB), para-phenylenediamine (pPD) and isoeugenol. We compared various protocols for induction of the CS reaction, differing by the site of induction, the number of applications and the concentrations of the 3 haptens. Comparison of the induction site for optimal CS reaction showed that, in Balb/c mice, the back was a better site of induction than the abdomen. Detection of the sensitizing properties of weak sensitizers (pPD, isoeugenol) was possible using an adjuvant-free protocol, provided that the induction phase comprised hapten applications on 3 consecutive days on the backs of animals. For DNCB, one application was sufficient to obtain optimal CS reaction. For all 3 haptens, a secondary response in vitro was obtained using semi-purified lymph node T cells from animals sensitized 5 days before with the optimized Mest. These results demonstrate that the Mest could be a useful experimental model for the study of all types of contact sensitizers.

Dissociation of allergenic and immunogenic functions in contact sensitivity to para-phenylenediamine

Contact sensitivity to para-phenylenediamine (PPD) is a frequent delayed-type hypersensitivity resulting in contact dermatitis. The aim of the present study, conducted in 16 patients allergic to PPD (as assessed by a positive patch test), was to get better insight into the mechanism of T-cell activation in PPD contact sensitivity. PPD was unable to induce significant proliferation of T cells from a first set of 9 patients. In 7 further patients, lymphocyte proliferation was assessed using PPD and 2 PPD metabolites, namely Brandrowski's base (BB) and benzoquinone (BQ). BB specifically stimulated T-cell proliferation in a dose-dependent fashion in all 7 patients whereas BQ, like PPD, was ineffective. The peripheral blood mononuclear cells (PBMC) of 8 PPD nonallergic individuals did not respond to either PPD, BB or BQ. We concluded from this study that: (1) the immunogenic hapten in PPD hypersensitivity is not PPD itself, and (2) BB might be the oxidative derivative of PPD endowed with T-cell-activating properties. Further support to this statement was provided by the observation that a T cell line derived from PBMC of a PPD-allergic patient in the presence of PPD responded to BB but not to PPD. Our in vitro results suggest that PPD is a prohapten which when applied on the skin is metabolized and converted into products (such as BB) which are the immunogenic haptens able to activate specific T cells.

Lack of oral tolerance but oral priming for contact sensitivity to dinitrofluorobenzene in major histocompatibility complex class II-deficient mice and in CD4+ T cell-depleted mice

Oral tolerance is defined by immune unresponsiveness after oral administration of soluble antigens and by antigen-specific inhibition of peripheral immune responses induced by prior antigen feeding. The aim of this study was to investigate the implication of the major histocompatibility complex (MHC) class II presentation pathway to CD4+ T cells in oral tolerance of contact sensitivity (CS) to the hapten dinitrofluorobenzene (DNFB). We used MHC class II knockout (AB0/0) and invariant chain knockout (Ii0/0) mice, which have, respectively, a total or partial defect in class II-restricted activation of CD4+ T cells, as well as normal C57BL/6 mice depleted of CD4+ T cells by injection of a specific antibody. Intragastric administration of DNFB prior to skin sensitization induced specific inhibition of contact sensitivity to DNFB in A beta +/0 and Ii+/0 heterozygotes comparable to that observed in C57BL/6 mice. In contrast, no oral tolerance was observed in either MHC class II-deficient A beta 0/0 and Ii0/0 homozygote mutants or in syngeneic anti-CD4-depleted C57Bl/6 mice. Moreover, a single oral administration of DNFB, without skin sensitization, could prime A beta 0/0, Ii0/0 as well as anti-CD4-depleted C57BL/6 mice for DNFB-specific CS. These findings demonstrate that the class II/CD4 pathway is involved in oral tolerance manifested both as the inhibition of CS by hapten feeding prior to skin sensitization, and as immune unresponsiveness of normal mice to oral administration of hapten. Furthermore, our data provide evidence that a single oral feeding with DNFB is able to prime mice for hapten-specific CS, provided that the class II/ CD4 pathway is bypassed.

T-cell repertoire analysis in chronic plaque psoriasis suggests an antigen-specific immune response

Psoriasis is a chronic inflammatory cutaneous disease of unknown etiology. Activation of T cells is thought to play a major role in the pathophysiology of psoriasis. In order to gain insight into the nature of the antigen (superantigen or nominal protein antigen) involved in psoriatic lesions, we have used a RT-PCR method to analyze the frequency of the 24 T cell receptor V beta chain (TCRBV) subfamilies and the size of the antigen-binding region (CDR3), using the immunoscope assay, in skin lesions of patients with chronic plaque-type psoriasis. Semi-quantitative analysis showed that no significant difference in V beta subfamily usage could be detected in T lymphocytes infiltrating lesional skin as compared to blood lymphocytes. Alternatively, determination of the size distribution of the CDR3 of all the V beta subfamilies revealed only in psoriatic skin a marked TCR oligoclonality defined by the presence in 3 to 5 V beta subfamilies of a single predominant CDR3 size which was associated with a unique V beta-J beta combination. Identical patterns of CDR3 length and V beta-J beta combination profiles were found in symetrical lesional sites from two psoriatic patients. This type of skewed CDR3 size profile is reminiscent of a local stimulation of T lymphocytes by nominal protein antigens. These data suggest that T lymphocytes infiltrating plaque-type psoriatic skin comprise expansions of oligoclonal T cells in response to stimulation by an antigen present in the skin.

Establishment of nickel-specific T cell lines from patients with allergic contact dermatitis: comparison of different protocols

Allergic contact dermatitis is a delayed-type hypersensitivity reaction, secondary to hapten-specific T lymphocyte activation in sensitized individuals. The present study reports on the establishment of T cell lines from peripheral blood mononuclear cells (PBMC) of nickel-allergic patients, initially cultured with nickel, IL-2, or PHA and IL-2. It was possible to derive hapten-specific T cell lines from the three protocols, and the best proliferative responses to nickel were observed when PBMC were cultured in the presence of nickel in vitro. T cell lines initially cultured with IL-2 always gave better specific proliferative responses to nickel than those derived with PHA and IL-2. Phenotypical analysis of the nickel-specific T cell lines showed that they were mainly composed of activated CD8+ TcR alpha beta + T lymphocytes. These results emphasize the importance of initial culture conditions for the generation of hapten-specific T cell lines and suggest that CD8+ lymphocytes could play an important role in the pathogenesis of allergic contact dermatitis.

Contact sensitivity in mice: differential effect of vitamin D3 derivative (calcipotriol) and corticosteroids

Vitamin D3 derivatives are new compounds used topically for the treatment of psoriasis. To get better insights into the mechanisms of action of these compounds, we studied the effect of local treatment with calcipotriol (vitamin D3 synthetic analogue) and compared it to that of betamethasone dipropionate in a murine contact sensitivity (CS) test, the Mouse Ear Swelling Test. Two haptens were used: oxazolone and paraphenylenediamine. Betamethasone and calcipotriol exerted a differential effect on the delayed-type hypersensitivity response. When drugs were applied to the abdomen (sensitization site) before sensitization, no effect was observed. When betamethasone was applied to the abdomen for 4 consecutive days after epicutaneous sensitization, a diminution of the CS response to the relevant hapten was observed, whereas calcipotriol given in the same conditions did not affect the reaction. Ointments were then administered to the ear (elicitation site) either for 4 consecutive days prior to the challenge, or for 4 days before and 2 days after the challenge. In both conditions, calcipotriol and betamethasone exerted a differential effect on elicitation, the latter inhibiting and the former increasing the CS response to oxazolone and paraphenylenediamine. From these results we conclude: (1) that vitamin D3 derivatives are devoided of immunosuppressive effects when applied topically, and (2) that clinical improvement of chronic inflammatory dermatoses observed with topical vitamin D3 derivatives and corticosteroids is due to different mechanisms.

Light-microscopic localization of somatostatin binding sites in the locus coeruleus of the rat

Somatostatin (SS14) binding sites within locus coeruleus (LC) were localized at the light microscope level by [125I][Tyr0,D-Trp8]SS14 radioautography combined with an immunohistochemical/neurotoxic lesioning approach. In intact rats, the dense accumulation of SS14 binding sites of LC conspicuously overlapped with the cluster of tyrosine hydroxylase (TH) immunoreactive neurons; SS14 specific binding was directly proportional to the number of TH immunostained (TH+) cell bodies per mg of tissue throughout LC. Complete lesion of catecholaminergic nerve cell bodies of LC by intracerebroventricular injection of 6-hydroxydopamine (6-OHDA) resulted in the total abolition of SS14 specific binding in the structure. In addition, specifically bound [125I][Tyr0, D-Trp8]SS14 and TH+ cell density were quantified serially in a set of rats bearing various partial neurotoxic lesions; a highly significant correlation was found between the two parameters at each of the 16 coronal levels of LC examined. The coefficient of proportionality was identical at all levels. These results strongly suggest that somatostatin binding sites are uniformly localized on all noradrenergic neurons of LC.

Effects of pontine lesions on brain stem polyneuronal activity during sleep in infant rats

Multiple-unit activity was recorded from residual neurons in the gigantocellular field ( FTG ) of the pontine reticular formation in young rats after extensive contralateral FTG lesions. Epochs of normal appearing active sleep continued to occur but were characterized by abnormally low FTG neuronal firing rates. In contrast, during epochs of active sleep with exaggerated motility, the FTG discharge frequencies approximated those observed during active wakefulness.

In vitro T cell response to staphylococcal enterotoxin B superantigen in chronic plaque type psoriasis

Recent studies have demonstrated the important role of CD4+ T cells in the pathophysiology of psoriasis. One of the current hypotheses is that triggering of the psoriatic inflammatory process could be secondary to CD4+ T cell activation by bacterial superantigens in the skin. In this study, IL-2-derived T cell lines were recovered from the blood and the skin of 4 patients with chronic plaque type psoriasis and of 2 patients with allergic contact dermatitis (ACD). Blood and skin T cell lines were tested for their ability to proliferate in vitro to staphylococcal enterotoxin B (SEB) presented by MHC class II expressing antigen-presenting cells. The results showed a significantly higher SEB-induced T cell proliferation in skin T cell lines as compared to blood T cell lines in 3 out of 4 psoriatic patients and in one of the 2 ACD patients. No difference between the skin and blood T cells for their response to phytohemagglutinin was observed. Furthermore the blood T cell lines from both patients and control individuals responded equally well to SEB. Thus psoriatic skin T cell lines were characterized by an enrichment in SEB-responding T cells. Since similar enhancement of SEB-responsive T cells was occasionally found in ACD patients, we propose that SEB could be an environmental factor associated with rather than responsible for psoriatic inflammation.

Differential Requirement for CD4 Help in the Development of an Antigen-Specific CD8+ T Cell Response Depending on the Route of Immunization

Previous studies in our laboratory have shown that DBA/2 mice injected i.p. with syngeneic P815 tumor cells transfected with the HLA-CW3 gene (P815-CW3) showed a dramatic expansion of activated CD8+CD62L− T cells expressing exclusively the Vβ10 segment. We have used this model to study the regulatory mechanisms involved in the development of the CW3-specific CD8+ response, with respect to different routes of immunization. Whereas both intradermal (i.d.) and i.p. immunization of DBA/2 mice with P815-CW3 cells led to a strong expansion of CD8+CD62L−Vβ10+ cells, only the i.d. route allowed this expansion after immunization with P815 cells transfected with a minigene coding for the antigenic epitope CW3 170–179 (P815 miniCW3). Furthermore, depletion of CD4+ T cells in vivo completely abolished the specific response of CD8+CD62L−Vβ10+ cells and prevented the rejection of P815-CW3 tumor cells injected i.p, whereas it did not affect CD8+CD62L−Vβ10+ cell expansion after i.d. immunization with either P815-CW3 or P815 miniCW3. Finally, the CW3-specific CD8+ memory response was identical whether or not CD4+ T cells were depleted during the primary response. Collectively, these results suggest that the CD8+ T cell response to P815-CW3 tumor cells injected i.p. is strictly dependent upon recognition of a helper epitope by CD4+ T cells, whereas no such requirement is observed for i.d. injection.

[Is triacetyl oleandomycin-ergotamine tartrate combination dangerous?]

The authors report a case of ischaemia of all four limbs in an adolescent following the simultaneous ingestion of triacetyl oleandomycin and ergotamine tartrate in low dosage. Two cases involving this same association of medications have appeared in the literature and attention is therefore drawn to the possible danger of use of these two drugs together.

Diode laser hair removal around ileo-colo ostomys is safe, effective and beneficial: a pilot study

BACKGROUND AND OBJECTIVE

Hair removal around an ileo-colo ostomy can cause a number of problems. We compared laser hair removal with mechanical shaving around the ostomy.

METHOD

Eleven patients were selected with hairy skin around the ostomy for therapy with an AlGaAs diode laser at 800 nm. Three to four treatments were given with an interval of 6 weeks.

RESULTS

Ten patients completed laser therapy. The average hair reduction was 60% based on visual inspection. Shaving frequency reduced from once a week to once every 6 weeks.

CONCLUSIONS

Laser hair removal likely becomes the preferred method in ostomy patients.