The BCL-6 gene is known to be located on chromosome 3q27, at the breakpoint of the 3q27-associated translocations that occur frequently in human non-Hodgkin's lymphomas (NHLs). To identify the BCL-6 protein, two antibodies that recognized distinct domains of this protein were raised in rabbits. Immunoprecipitation and immunoblotting of lysates of BCL-6-expressing cells using both antibodies showed a broad 92- to 98- kD band. Dephosphorylation of BCL-6 protein reduced the size of this band to 87 kD, suggesting that BCL-6 may be expressed in a phosphorylated form. Immunostaining with both antibodies showed that BCL-6 protein was localized in the nuclei of most of the germinal center B cells and a small number of marginal zone B cells. Furthermore, BCL-6 protein was expressed in follicular, Burkitt's, and diffuse large B-cell lymphomas. These results suggest that the BCL-6 protein, expressed in B cells of the germinal centers which are important in the maturation of immune responses, may play some physiological role(s) in the germinal center B cells.

We demonstrated in the present study that the BCL-6 tranof B cell maturation. However, it is still uncertain whether scripts were detectable not only in B cells, but also in circulat-BCL-6 protein may be expressed during the differentiation of atmosphere with 5% CO 2 at 37°C.

Bcl-6 protein is a recently identified novel transcription factor whose deregulated expression is associated with diffuse large B cell lymphomas. It was recently shown by us that the protein is located in germinal center B cells and their neoplastic counterparts. In the present study, the expression of bcl-6 protein on normal epidermis, benign, and malignant tumors originating from epidermal cells, and squamous cell carcinoma (SCC) cell lines are investigated. With the use of immunohistochemistry, bcl-6 protein was shown to stain intensely on normal prickle cells, but none to only slightly on epidermal basal cells. Papillomas and keratoacanthomas copied their normal counterparts in the mode of expression. Various levels of expression were found on seborrheic keratoses, while the expression level on basal cell epitheliomas was low. Peculiarly, eccrine poromas and undifferentiated spindle-shaped basal cell epitheliomas were totally unstained. Squamous cell carcinomas showed a variety of expression levels, while two undifferentiated spindle-shaped carcinomas and one undifferentiated SCC cell line remained unstained. These results suggest that the expression of bcl-6 protein may be associated with morphological differentiation in normal and neoplastic epidermal cells.

A 74-year-old male, who had been treated with artificial pneumothorax for pulmonary tuberculosis 38 years before, was admitted with fever on May 1992. Chest X-ray revealed the presence of scarred empyema in the right thorax, whereas the abdominal computed tomography indicated the presence of tumor extending from the pleural wall to the liver. The aspirated pleural effusion was suggestive of malignant lymphoma. He died in september 1992. Autopsy revealed non-Hodgkin's malignant lymphoma of pleural origin involving lower half of right pleura, right diaphragm and right upper abdominal cavity including the right lobe of the liver. Histologically was diffuse large cell type non-Hodgkin's lymphoma according to the LSG classification, showing B cell phenotype on immunohistologic studies. In addition, Epstein-Barr virus (EBV) genome, EBERs, EBNA2 (strong) and LMP (weak) proteins were detected by PCR, in situ hybridization and immunology, respectively, indicating the association of EBV with lymphomagenesis in this case.