Plasma cells tumors decrease CD23 mRNA expression in vivo in murine splenic B cells.
CD23, the low-affinity Fc receptor for IgE, is constitutively expressed on mature, naive B cells, but is lost following B cell activation. We and others have shown that CD23 expression on B cells decreases in mice bearing plasma cell tumors. In contrast to these findings, we find that IgE-secreting tumors do not cause a loss of CD23 expression on host splenic B cells. Decreased expression of CD23 on B cells induced by plasma cell tumors requires direct contact between tumor cells and B cells; and other host cells are not involved. The loss of surface CD23 expression is associated with a decrease in steady-state CD23 mRNA levels in B cells from plasma cell tumor-bearing mice. Interestingly, loss of CD23 mRNA is observed even in B cells from mice with IgE-secreting tumors, where we find surface CD23 protein expression to be similar to that of normal mice. The maintenance of surface CD23 expression on B cells in mice with IgE-secreting tumors is dependent solely on the presence of IgE, and is not a tumor-specific effect. Therefore, we conclude that in vivo, IgE secreted by plasma cell tumors can result in the maintenance of normal levels of surface CD23 expression by a post-transcriptional mechanism, even when the tumor induces a down-regulation of CD23 mRNA levels.
Ruzek
M C
MC
Department of Microbiology, University of Minnesota, Minneapolis 55455, USA.
Mathur
A
A
D000818:Animals; D001402:B-Lymphocytes / Q000378:metabolism; D015152:Blotting, Northern; D002478:Cells, Cultured; D015536:Down-Regulation / Q000502:physiology; D005260:Female; D015870:Gene Expression; D007073:Immunoglobulin E / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D010954:Plasmacytoma / Q000235:genetics* / Q000503:physiopathology*; D012333:RNA, Messenger / Q000032:analysis*; D017455:Receptors, IgE / Q000235:genetics*; D013154:Spleen / Q000166:cytology
D012333:RNA, Messenger; D017455:Receptors, IgE; D007073:Immunoglobulin E