Maintenance of the CD40-related immunodeficient response in hyper-IgM B cells immortalized with a LMP1-regulated mini-EBV.
Our previous investigation of a patient (pt1) with non-X-linked hyper-immunoglobulin M syndrome revealed a CD40-mediated defect in B cell activation that resulted in low CD23 expression and absence of germ-line transcription and class-switch recombination. These deficiencies were complemented in vitro by a high threshold of sustained signaling through CD40. To further analyze the signaling defect in pt1 B cells, two types of Epstein-Barr virus lymphoblastoid cell lines (LCLs) were generated that either constitutively expressed the viral transforming protein latent membrane protein-1 (LMP1; pt1-LCL) or expressed it under the control of a tet-inducible promoter (pt1-LCL(tet)). Because LMP1 signals through the CD40 pathway, the pt1-LCL and pt1-LCL(tet) lines allow comparison of downstream functions in response to either constitutive LMP1 signals or regulated LMP1 and CD40 signals. Immortalized pt1-LCLs were initially CD23(lo)/CD38(hi) and reverted to a CD23(hi)/CD38(lo) phenotype upon extended growth in culture, suggesting that the CD40 defect was reversed by selection and/or constitutive expression of LMP1. In contrast, pt1-LCL(tet) cells retained the CD23(lo)/CD38(hi) phenotype after extended periods of culture and failed to up-regulate CD23 in response to CD40 signals. Analysis of pt1-LCL(tet) cells in response to the CD40 signals in the presence or absence of LMP1 revealed that mitogenic activation resulted only from LMP1 and not CD40, indicating a difference in the response of pt1 B cells to these two distinct signals. Together, these data demonstrate that the pt1-LCL(tet) cells maintain the CD40-related defect and provide a unique approach to study the independent effects of LMP1- and CD40-directed signals.
Lu
Kristina T
KT
Nelson Biological Laboratories, Rutgers, The State University of New Jersey, 604 Allison Road, Piscataway, NJ 08854, USA.
Dryer
Rebecca L
RL
Song
Charles
C
Covey
Lori R
LR
D051997:ADP-ribosyl Cyclase 1 / Q000096:biosynthesis / Q000235:genetics; D001402:B-Lymphocytes / Q000276:immunology* / Q000821:virology; D019013:CD40 Antigens / Q000276:immunology*; D002461:Cell Line, Transformed; D006801:Humans; D007075:Immunoglobulin M / Q000096:biosynthesis / Q000276:immunology*; D007153:Immunologic Deficiency Syndromes / Q000276:immunology*; D010641:Phenotype; D017455:Receptors, IgE / Q000096:biosynthesis / Q000235:genetics; D015398:Signal Transduction / Q000276:immunology; D014763:Viral Matrix Proteins / Q000235:genetics / Q000276:immunology*
D019013:CD40 Antigens; C037662:EBV-associated membrane antigen, Epstein-Barr virus; D007075:Immunoglobulin M; D017455:Receptors, IgE; D014763:Viral Matrix Proteins; D051997:ADP-ribosyl Cyclase 1