Humans are continually inhaling environmental fungi. When the host immune system is competent, the inhaled fungi are cleared away from the lung by host defense mechanisms. But in immunocompromised individuals, the environmental fungi (e.g., Aspergillus fumigatus) sometimes cause infection. Pathogenic fungi possess various mechanisms to invade the host. A. fumigatus is no exception in possessing several virulence factors and defense mechanisms against host immune attack.
One of the virulence factors is secondary metabolite. A. fumigatus produces a variety of secondary metabolites, and the fungal products in culture supernatant have a strong apoptosis-inducing activity to macrophages and alveolar epithelial cells. These data suggest that A. fumigatus is equipped with special projectile weapons for destroying host physical barriers and immunological barriers in lung.
The fungal cell wall is an easy target for the host to recognize the pathogen. One of the fungal cell wall components, β- (1,3) -glucan, is a major fungal PAMP (pathogen-associated molecular pattern), which is recognized by one of the pattern recognition receptors, dectin-1. The interaction induces activation of transcription factors and production of proinflammatory cytokines in the host cell. However, β-glucan of A. fumigatus is strongly exposed to the surface only during the “ swollen-conidia ” phase. In the hyphal phase, the fungus is covered with “ armor ”, i.e., other cell wall components to minimize the exposure of the β-glucan structure. These findings suggest that A. fumigatus evades the recognition and the attack from host by masking β-glucan.
A. fumigatus has clever mechanisms to defend itself and to attack the host immune system.

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Malassezia yeasts are part of the cutaneous microflora and are also associated with a number of skin diseases such as pityriasis versicolor, seborrheic dermatitis, and atopic dermatitis (AD). Among organisms of the Malassezia species, M. globosa and M. restricta are highly associated with AD. However, their precise role in AD has remained uncertain. We first attempted to identify major allergens from M. globosa using a proteomics analysis. Immunoblotting showed that IgE-reactive components with molecular masses of 40-45 kDa proteins were detected by 100% (28 of 28) of sera from AD patients. The IgE-reactive allergens corresponding to the 42 kDa protein (MGp42) were identified by two-dimensional immunoblotting, and partially sequenced by MALDI-TOF MS with post source decay (PSD) of the peptide digest. Comparison of sequences with known protein sequences revealed that MGp42 showed similarity to the heat shock protein (hsp) family. Our studies have also demonstrated that human keratinocytes responded to the two Malassezia species with different Th2-type cytokine profiles, i.e. M. globosa induced IL-5, IL-10, and IL-13 secretion from the keratinocytes, whereas M. restricta induced IL-4 secretion. These findings suggest that M. globosa and M. restricta play a synergistic role in triggering or exacerbating AD by stimulating the Th2 immune response.

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Infections with dermatophytes are generally confined to the keratinized stratum corneum. This superficial site of infection may protect the infecting dermatophytes from direct contact with some of the effector cells of the immune system; therefore, the immune system has developed a special subsystem in the skin to eliminate them.
The innate immunity and acquired immunity (delayed-type hypersensitivity response) are both required for cutaneous immune surveillance against dermatophytes in the skin.
Epidermal keratinocytes not only have an important structural role in forming a physical barrier to dermatophytes but also are important functionally in mediating cutaneous immune reactions. These cells can secrete proinflammatory cytokines, chemokines, and anti-microbial peptides in response to dermatophytes. The T cell-mediated delayed-type hypersensitivity response to dermatophyte antigens may play a central role in both pathogenesis of the typical skin lesions and an acquired, relative resistance that affords partial immunity to the host. However, the exact form of effector T cell immunity and the cellular and molecular mechanisms which eliminate dermatophytes from the skin are poorly understood. The literature on the immunology against dermatophyte infection is reviewed in this paper.

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We report a case of kerion celsi caused by Microsporum gypseum and present some epidemiological statistics and a distribution of the mating types of M. gypseum . A 10-year-old healthy boy living in Narita, Chiba Prefecture, visited the Narita Red Cross Hospital in October 2004 with complaints of a scaly erythematous plaque and alopecia. Before the visit, he had been treated with steroid lotions and antibiotics without success. A direct examination of the diseased hair shaft using a potassium hydroxide (KOH) solution revealed the presence of fungal hyphae outside the hair shafts. The patient showed a positive reaction to the trichophytin test. The fungus isolated from the lesion was identified as M. gypseum on the basis of its morphological and physiological characteristics and the results of molecular biological analysis. The sequence of the gene coding for the internal transcribed spacer (ITS) 1 region of ribosomal RNA (ITS 1 rDNA) was homologous to that of Arthroderma gypseum (DDBJ accession no. AB193684). The isolate was confirmed to be A. gypseum (-) mating type on the basis of crossing experiments with (+) and (-) mating types of A. gypseum, A. incurvatum , and A. fluvum . The patient was successfully treated with 50 mg/day (1.6 mg/kg/day) of itraconazole for 4.5 months.

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Twelve cases of tinea capitis were encountered at a clinic in Kumamoto prefecture between April 2004 and December 2008. Patients were boys aged between 2 and 18 in 11 cases, and a woman aged 50 years in 1 case. The pathogen was Microsporum canis in 6 cases, and Trichophyton tonsurans in 6 cases. In the cases with M. canis , patients were boys aged 2 to 8 years in 5 cases, and the type of disease was non-inflammatory in 5 cases and inflammatory in 1 case. The patients with T. tonsurans were boys aged 12 to 18 years (judo athletes in 5 cases) and the type of disease was inflammatory in 2 cases and black dot in 4 cases. Three of the M. canis cases were treated with oral administration of itraconazole (ITCZ) at doses of 2.4-4.0 mg/kg/day, and the other 3 with terbinafine hydrochloride (TBF) at doses of 2.6-4.6 mg/kg/day. The duration of treatment was 8-14 weeks with ITCZ, and 4-8 weeks with TBF. In the T. tonsurans cases, TBF was orally administered at doses of 1.4-2.4 mg/kg/day for a period of 8-12 weeks. In one case of non-inflammatory M. canis infection (Case 6) and one case of inflammatory T. tonsurans infection (Case 10), treatment was initiated with the dose recommended in Japan, but symptoms did not improve; therefore the dose was doubled according to European and American guidelines and the patients recovered. As tinea capitis frequently resists treatment, establishment of treatment guidelines is necessary.

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Because of its high discriminatory potential, fragment analysis of microsatellites has been frequently used for genotyping of Candida albicans at the strain level. In order to evaluate a genotyping system based on the fragment analysis of microsatellites combined with PCRs targeting 25S rDNA and RPS, 456 independent strains of C. albicans were subjected to genotype analysis using 4 microsatellite markers (CDC3, HIS3, CA I and CA III), followed by 25S rDNA and RPS-based genotyping. The fragment analysis using CA I showed the highest discriminatory potential (DP=0.9782), followed by HIS3 (DP=0.8780). Using combined microsatellite markers, 456 C. albicans strains were divided into 384 genotypes (DP=0.9984). PCRs targeting 25S rDNA and RPS were performed to differentiate the strains that showed identical genotypes in the fragment analysis, resulting in 434 genotypes (DP=0.9996). The combined genotyping system showed high discriminatory power at the strain level, and therefore is useful for rapid genotyping in molecular epidemiological studies of candidiasis.

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Genetic heterogeneity and drug susceptibility patterns of 43 Candida albicans isolates from patients with respiratory infections in China were compared with those of 52 isolates from Japanese patients. Of the 43 strains, 17 were genotype A, 17 were genotype B, 8 were genotype C, and 1 was genotype E. Drug susceptibilities against amphotericin B, flucytosine, 3 azoles, and micafungin of the 43 strains and the 52 Japanese isolates were compared. All strains in China were susceptible to all drugs tested, and susceptibility patterns of the two countries were similar. Four Japanese isolates showed trailing growth for azole antifungals; Chinese strains did not.

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