Viral proteins of gamma-2 herpesviruses, such as LMP2A of Epstein Barr virus (EBV) and Tip of herpesvirus saimiri (HVS) dysregulate lymphocyte signaling by interacting with Src family kinases. K15 open reading frame of Kaposi's sarcoma associated herpesvirus (KSHV), located at the right end of the viral genome, encodes several splicing variants differing in numbers of transmembrane domains. Previously, we demonstrated that the cytoplasmic tail of the K15 protein interfered with B cell receptor signal transduction to cellular tyrosine phosphorylation and calcium mobilization. However, the detailed mechanism underlying this phenomenon was not understood. In the C-terminal cytoplasmic region of K15, putative binding domains for Src-SH2 and -SH3 were identified. In this study, we attempted to characterize these modular elements and cellular binding protein(s) by GST pull down and co-immunoprecipitation assays. These studies revealed that K15 interacted with the major B cell tyrosine kinase Lyn. In vitro kinase and transient co-expression assays showed that the expression of K15 protein resulted in activation of Lyn kinase activity. In addition, GST pull down assay suggested that the SH2 domain of Lyn alone was necessary for interaction with the C-terminal SH2B (YEEV) of K15, but the addition of Lyn SH3 to the SH2 domain increases the binding affinity to K15 protein. The data from luciferase assays indicate that K15 expression in BJAB cells induced NFAT and AP1 activities. The tyrosine residue in the C-terminal end of K15 required for the Lyn interaction appeared to be essential for NFAT/AP1 activation, highlighting the significance of the C-terminal SH2B of K15 as a modular element in interfering with B lymphocyte signaling through interaction with Lyn kinase.
Cell Line ; Herpesvirus 8, Human/genetics/*metabolism ; Humans ; Immunoblotting ; Immunoprecipitation ; Membrane Proteins/genetics/*metabolism ; NFATC Transcription Factors/genetics/*metabolism ; Phosphorylation ; Protein Binding ; Sarcoma, Kaposi/virology ; Transcription Factor AP-1/genetics/*metabolism ; Transfection ; Viral Proteins/genetics/*metabolism ; src-Family Kinases/genetics/*metabolism

OBJECTIVESTo study the clinicopathologic features of Rosai-Dorfman disease (RDD), expression of various antigens, human herpes virus type 8 (HHV8), human papillomavirus (HPV)-DNA and Epstein-Barr virus (EBV)-mRNA, and compare the findings with those in the literature.

METHODSThe clinicopathologic findings of 16 Rosai-Dorfman disease cases were retrospectively reviewed. Immunohistochemical study for S-100 protein, CD68 (PG-M1), CD163, CD21, CD1a, CD20, CD45RO, CD4, CD8, M-CSF and HHV8 was carried out in 9 of the 16 cases. In-situ hybridization for EBV-mRNA and HPV-DNA was also performed.

RESULTSThe male-to-female ratio of the patients was 4.33:1. Amongst the 16 cases studied, 62.5% (10/16) presented nodal RDD, with cervical lymph node predominantly involved. Half of these cases had affected lymph nodes in more than one anatomic site. Extranodal RDD represented 37.5% (6/16) of the cases. The relapse rate of extranodal RDD was higher than that of nodal RDD. Histologically, nodal RDD was characterized by dilated sinuses filled with large polygonal histiocytes which contained lymphocytes and plasma cells. For extranodal lesions, various degrees of stromal fibrosis were seen in association with mixed inflammatory cells (especially plasma cells). The large polygonal histiocytes varied in number and were distributed in clusters or patches. Immunohistochemical study showed that the abnormal histiocytes were strongly positive for S-100 protein. They also expressed CD68, CD163 and M-CSF, but were negative for CD1a, CD21 and HHV8. The lymphocytes in cytoplasm of these histiocytes were positive for both T and B cell markers (with T cell predominance, including a mixture of CD4- and CD8-positive cells). HPV-DNA and EBV-mRNA were not detected by in-situ hybridization. To date, 62 cases of RDD have been reported in mainland China, including 34 cases of nodal RDD and 18 cases of extranodal RDD. The remaining 10 cases involved both lymph nodes and extranodal sites. Compared with overseas reports, RDD occurring in China tended to affect older patients and with slight male predilection.

CONCLUSIONSRosai-Dorfman disease is relatively rare in China. Pathologic diagnosis of extranodal RDD may be difficult. The demographic data of RDD in China, including age and sex of patients, are different from those in the literature.

Adolescent ; Adult ; Aged ; Antigens, CD ; metabolism ; Antigens, Differentiation, Myelomonocytic ; metabolism ; Bone Diseases ; metabolism ; pathology ; virology ; Child ; DNA, Viral ; analysis ; Female ; Follow-Up Studies ; Herpesvirus 8, Human ; genetics ; isolation & purification ; Histiocytosis, Sinus ; metabolism ; pathology ; virology ; Humans ; Immunohistochemistry ; Lymph Nodes ; pathology ; Macrophage Colony-Stimulating Factor ; metabolism ; Male ; Middle Aged ; Nose Diseases ; metabolism ; pathology ; virology ; RNA, Viral ; analysis ; Receptors, Cell Surface ; metabolism ; Retrospective Studies ; S100 Proteins ; metabolism ; Skin Diseases ; metabolism ; pathology ; virology ; Young Adult