Participation of Tumor-Associated Myeloid Cells in Progression of Amelanotic Melanoma (RMM Tumor Line) in F344 Rats, with Particular Reference to MHC Class II- and CD163-Expressing Cells.

Tumor progression is often influenced by infiltration of myeloid cells; depending on the M1- or M2-like activation status, these cells may have either inhibitory or promoting effects on tumor growth. We investigated the properties of tumor-associated myeloid cells in a previously established homotransplantable amelanotic melanoma (RMM tumor line) in F344 rats. RMM tumor nodules were allowed to reach the sizes of 0.5, 1, 2 and 3 cm, respectively. Immunohistochemistry and flow cytometry was performed for macrophage markers CD68 and CD163, and for the antigen-presenting cell marker, MHC class II. Although no significant change was observed in the number of CD68+ and CD163+ macrophages during RMM progression, the number of MHC class II+ antigen-presenting cells was reduced in 3 cm nodules. Real-time RT-PCR of laser microdissection samples obtained from RMM regions rich in MHC class II+ cells demonstrated high expressions of M1-like factors: IFN-γ, GM-CSF and IL-12a. Furthermore, fluorescence-activated cell sorting, followed by real-time RT-PCR for CD11b+ MHC class II+ (myeloid antigen-presenting cells), CD11b+ CD163+ (M2 type myeloid cells), CD11b+ CD80+ (M1 type myeloid cells) and CD11b+ CD11c+ (dendritic cells) cells was performed. Based on the levels of inflammation- and tumor progression-related factors, MHC class II+ antigen-presenting cells showed polarization towards M1, while CD163+ macrophages, towards M2. CD80+ and CD11c+ myeloid cells did not show clear functional polarization. Our results provide novel information on tumor-associated myeloid cells in amelanotic melanoma, and may become useful in further research on melanoma immunity.

Cutaneous Histiocytic Sarcoma with Regional Lymph Node Metastasis in a Netherland Dwarf Rabbit (Oryctolagus cuniculus).

A 10-year-old male Netherland dwarf rabbit (Oryctolagus cuniculus) was presented with a red nodular mass (1 cm in diameter) with ulceration and hair loss in the skin of the left upper lip. Cytological examination revealed atypical round cells. The mass was excised surgically. Histologically, the mass was composed of large round to polyhedral neoplastic cells with marked cytological atypia. The neoplastic cells were often binucleated or multinucleated. Immunohistochemically, the neoplastic cells were intensely positive for Iba1 and vimentin, but fewer neoplastic cells expressed E-cadherin. Nuclear immunoreactivity for Ki67 was detected in approximately 41% of the neoplastic cells. Metastasis to the left cervical lymph nodes was detected 6 months after the surgical excision. Based on clinical, histopathological and immunohistochemical findings, the present case was diagnosed as cutaneous histiocytic sarcoma. To the authors' knowledge cutaneous histiocytic disease has not been reported previously in lagomorphs.

Metastatic Liposarcoma in a South African Fur Seal (Arctocephalus pusillus).

A 14-year-old female South African fur seal (Arctocephalus pusillus) was presented with a large skin mass on the right shoulder. At necropsy examination, multiple white nodules were found in the lungs, liver, spleen and right axillary lymph nodes. Histologically, the skin mass was composed of round to polygonal neoplastic cells with round to oval nuclei and variably sized cytoplasmic vacuoles. Cellular and nuclear atypia were prominent. Immunohistochemically, the neoplastic cells expressed vimentin, but not cytokeratins, S100 protein, adipophilin or desmin. The cytoplasmic lipid droplets stained positively with oil red O. Metastasis was seen in the lungs, liver, spleen and right axillary lymph nodes, with similar morphological features to the skin mass. Based on these findings, a diagnosis of a pleomorphic liposarcoma with systemic metastasis was made. No previous reports of metastatic liposarcomas have been published in marine mammals.

Isolation and serotyping of dengue viruses by mosquito inoculation technique from clinically suspected cases of dengue fever.

Dengue virus was isolated from 44 clinically suspected cases of dengue fever by mosquito inoculation technique using Aedes aegypti mosquito in the department of virology, BSMMU in the year 2000. Identification of dengue virus was done by direct fluorescent antibody technique using FITC conjugated anti-dengue monoclonal antibody and serotyping was carried out by indirect fluorescent antibody technique using serotype specific monoclonal anti-dengue antibody. The dengue virus isolation rate was 41.9%. The result of serotyping revealed circulation of all four serotypes of dengue viruses in Dhaka, Bangladesh and DEN-3 was the predominant (70.5%) serotype during the outbreak in 2000. The rate of isolation was higher in patient's serum at an early stage of fever (p<0.01) and with higher body temperature (p<0.01). The rate of isolation was 77.77% in patient's serum collected on the 1st day of fever, and then the rate gradually declined and lowest (16.6%) on the 5th day of fever. The mosquito inoculation technique is an easy, economical and sensitive method for dengue virus isolation and is recommended for routine virological surveillance in laboratories of Bangladesh where sophisticated facilities are limited.