Beate M. Czarnetzki

Recruitment of neutrophils is a common feature in diseases that are associated with mast cell activation. The mechanisms that mediate neutrophil activation are not well understood. IL-8 is a recently described potent chemotactic factor that might be pathogenetically involved in this process. We therefore studied the human mast cell line HMCI and human skin mast cells for their ability to produce IL-8 using various stimuli. IL-8-mRNA was expressed in a stimulus- and time-dependent fashion as detected by Northern blot analysis with an IL-8-specific cDNA probe. The molecular mass of HMCI-derived IL-8 was determined to be about 8 kDa by immunoblot analysis. Immunoreactive and biologically active IL-8 protein was measured in the cell culture supernatants of HMCI cells by an ELISA and a chemotaxis assay, respectively. On immunoelectron microscopy of stimulated skin mast cells, IL-8 was found along cytoplasmatic membranes and in intracellular granules. Our data indicate that mast cells may contribute to neutrophil recruitment by secretion of IL-8.

In chronic urticaria, the possible pathogenetic role of pseudoallergic reactions to food has been repeatedly discussed, but stringent prospective studies regarding their clinical significance are not available. All patients with chronic urticaria and/or angioedema hospitalized at the department of dermatology during a period of 2 years were therefore included in a prospective study. Patients (n = 64) were screened for common causes of urticaria and then evaluated for possible benefits of a stringently controlled pseudoallergen-free diet. Double-blind, placebo-controlled oral provocation tests with food additives were performed on those patients benefitting from diet. In 73% of patients, symptoms ceased or were greatly reduced within 2 weeks on diet, although only 19% of them responded to individual pseudoallergens on provocation tests. Of the remaining patients, 11% responded to treatment of an associated inflammatory disease, and in 16%, no cause of the urticaria was ascertained. Follow-up at 6 months after hospitalization showed complete remission on diet in 46% and lasting improvement in all but one of the remaining patients on diet. An additive-free, stringently controlled diet thus provides a simple means of diagnosing and treating the majority of patients with chronic urticaria.

The etiology of alopecia areata (AA), a putative autoimmune disease characterized by sudden hair loss, has remained obscure. It is not understood, how the characteristic inflammatory infiltrate that selectively attacks anagen hair follicles in AA is generated. We hypothesize that this reflects an unexplored form of autoimmunity, a cytotoxic T cell attack on rhythmically synthesized autoantigens normally sequestered by a lack or very low level of MHC class I (MHC I)-expression, and suggest the following mechanism of AA pathogenesis: Microtrauma, neurogenic inflammation, or microbial antigens cause a localized breakdown of MHC I-"negativity" in the proximal anagen hair bulb via proinflammatory cytokines. This exposes autoantigens derived from melanogenesis-related proteins (MRP-DP), which are only generated during anagen, and triggers two successive waves of autoimmune responses: CD8+ cytotoxic T cells initiate AA after recognizing MRP-DP abnormally presented by MHC I molecules on hair matrix melanocytes and/or keratinocytes; a secondary attack, carried by CD4+ T cells and antigen presenting cells, is then mounted against MHC class II--presented additional autoantigens exposed by damaged melanocytes and keratinocytes. The latter causes most of the follicular damage, and extrafollicular disease, and depends greatly on the immunogenetic background of affected individuals. This unifying hypothesis explains the clinical heterogeneity and all salient features of AA, and argues that only the unlikely coincidence of multiple predisposing events triggers AA. The suppression of MHC I--expression and synthesis of MRP in the hair bulb, and the "tolerization" of MRP-DP autoreactive CD8+ T cells may be promising strategies for treating AA.

For unknown reasons, the pilosebaceous unit displays prominent alkaline phosphatase (AP) activity, and alterations in AP activity are seen in alopecia areata. The role of AP in hair biology and pathology has been obscured by contradictory reports on the localization and activity of AP during the hair cycle, and by a paucity of instructive models for studying AP functions. Using the C57 BL-6 mouse model for hair research, we have characterized endogenous AP with a simple histochemical developing solution routinely employed for AP immunohistology. This method was selective for AP, and revealed distinctive hair cycle-dependent changes in AP activity and localization. Although the dermal papilla displays unusually strong AP activity during the entire hair cycle, the outer root sheath is AP-positive only during late anagen and early catagen. Strong, rather homogeneous AP activity is seen in the sebaceous gland (SG) only during catagen and telogen. This AP staining pattern indicates hair cycle-dependent changes in SG functions, and differs to some extent from the previously reported AP activity during the hair cycle of various species. We propose a simple and effective technique for follicle classification based on the AP histochemistry of dermal papilla and sebaceous gland, and discuss uses of the C57 BL-6 mouse model for functional AP studies.

We introduce cyclophosphamide-induced alopecia (CYP-IA) in C57BL-6 mice as a clinically relevant model for studying the biology of chemotherapy-induced alopecia and for developing anti-alopecia drugs. One injection of CYP to mice with all back skin follicles in anagen VI induces severe alopecia that strikingly reproduces the follicle response, recovery, and histopathology seen in human CYP-IA. CYP dose-dependently induces abnormal follicular melanogenesis and dystrophic anagen or, in more severely damaged follicles, dystrophic catagen. Both dystrophy forms are followed by an extremely shortened telogen phase, but differ in the associated hair loss and in recovery patterns, which determines hair regrowth. This follicular response to CYP can be manipulated pharmacologically: systemic cyclosporine A shifts it toward a mild form of dystrophic anagen, thus retarding CYP-IA and prolonging "primary recovery". Topical dexamethasone, in contrast, forces follicles into dystrophic catagen, which augments CYP-IA, but accelerates the regrowth of normally pigmented hair ("secondary recovery").