CD43 cross-linking increases the Fas-induced apoptosis through induction of Fas aggregation in Jurkat T-cells

CD43 (sialophorin, leukosialin) is a heavily sialylated surface protein expressed on most leukocytes and platelets including T cells. Although CD43 antigen is known to have multiple and complex structure, exact function of CD43 in each cell type is not completely understood. Here we evaluated the role of CD43 in Fas (CD95)-induced cell death in human T lymphoblastoid cell line, Jurkat. Crosslinking CD43 antigen by K06 mAb increased the Fas-mediated Jurkat cell apoptosis and the augmentation was inhibited by treatment with caspase inhibitors. Further, CD43 signaling of Jurkat cells induced Fas oligomerization on the cell surfaces implying that CD43 ligation have effects on early stage of Fas-induced T cell death. These also suggest that CD43 might play an important role in contraction of the immune response by promotion of Fas-induced apoptosis in human T cells.

Expression of CD43 in Colorectal Adenocarcinom

BACKGROUND: CD43 is a sialoglycoprotein that is highly expressed on most leukocytes, except on B lymphocytes and dendritic cells. CD43 has been reported to be involved in the adhesion and apoptosis of lymphocytes. Although the aberrant expression of CD43 antigen in non-lymphoid tissues has been reported, the expression of the CD43 antigen in gastrointestinal malignancies is not well studied. Here, we studied the expression of CD43 in colon adenocarcinoma using the anti-CD43 monoclonal antibody developed in our laboratory. METHODS: Thirty patients who had undergone surgical resection for colorectal carcinoma were recruited. The expression of CD43 molecule was determined by analyzing the formalin-fixed, paraffin-embedded specimens immunohistochemically using our newly developed anti-CD43 mAb (K06). The results obtained by the immunohistochemical analysis correlated to the clinicopatho-logical parameters. RESULTS: The expression of CD43 were found in 20 out of 30 colorectal carcinoma cases. The expression of CD43 antigen is higher in well differentiated adenocarcinomas than poorly or moderately differentiated adenocarcinomas. CONCLUSIONS: The new anti-CD43 mAb might be helpful for the detection of the expression of CD43 on colorectal carcinoma cells. Further studies are required to assess the relationship between the CD43 expression and the colorectal carcinogenesis.

Distinct Patterns of Cleavage and Translocation of Cell Cycle Control Proteins in CD95-induced and p53-induced apoptosis

Apoptotic cell death induced by p53 occurs at a late G1 cell cycle checkpoint termed the restriction(R)point, and it has been proposed that p53-induced apoptosis causes upregulation of CD95. However, as cells with defective in CD95 signaling pathway are still sensitive to p53-induced apoptosis, CD95 cannot be the sole factor resulting in apoptosis. In addition, unlike p53-induced apoptosis, the relationship between CD95-mediated apoptosis and the cell cycle is not clearly understood. It would there-fore be worth investigating whether CD95-mediated cell death is pertinent with p53-induced apoptosis in view of cell cycle related molecules. In this report, biochemical analysis showed that etoposide-induced apoptosis caused the induction and the nuclear translocation of effector molecules involved in G1 cell cycle checkpoint. However, there was no such translocation in the case of CD95-mediated death. Thus, although both types of apoptosis involved caspase activation, the cell cycle related proteins responded differently. This argues against the idea that p53-induced apoptosis occurs through the induction of CD95/CD95L expression.

The Differential Staging of Murine Thymic Lymphoma Cell Lines, Scid.adh, R1.1 and EL-4

BACKGROUND: Scid.adh is a recently developed murine thymic lymphoma cell line, which has been used as in vitro model for the study of double negative stage III thymocytes. In this study, we compared the expression profile of a number of genes and proteins, which are tightly related to T cell development and apoptosis, in thymic lymphoma cell lines, R1.1, EL-4, and Scid.adh for the developmental staging. METHODS: We examined the expression of development marker genes and proteins in three lymphoma cell lines by flow cytometry and RT-PCR. In addition, the expression of apoptosis-related molecules including bcl-2, bax and Fas was also investigated. RESULTS: As previously reported, Scid.adh cell line expressed CD8 and CD25 but not TCR alpha chain, while R1.1 cells expressed TCR alpha chain and both CD4 and CD8 transcripts. These suggest that R1.1 might be in double positive stage, and low level of CD44 expression and the absence of CD25 support this suggestion. In contrast, EL-4 cells showed high level of TCR alpha chain transcript, and low-level of CD4 expression, suggesting that EL-4 is in more mature stage than R1.1. Further, this suggestion was supported by the lack of mT-20 in EL-4 cells, which is expressed in the immature thymocytes, and Scid.adh and R1.1 cell lines, but not in the terminally differentiated thymocytes and peripheral T cells. Among the apoptosis-related gene, transcripts of bcl-2 gene were detected in both R1.1 and EL-4 but not in Scid.adh cells, while bax was expressed in all cell lines. Fas expression was the highest in EL-4 cells and low in Scid.adh cell line. CONCLUSION: R1.1 cell may represent double positive stage, and EL-4 is more differentiated cell line. In addition, Scid.adh and EL-4 cell lines are suspected to be useful for the study of function of bcl-2 family and Fas during the thymocyte development, respectively.