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Maintenance of the CD40‐related immunodeficient response in hyper‐IgM B cells immortalized with a LMP1‐regulated mini‐EBV
Author(s) -
Lu Kristina T.,
Dryer Rebecca L.,
Song Charles,
Covey Lori R.
Publication year - 2005
Publication title -
journal of leukocyte biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.819
H-Index - 191
eISSN - 1938-3673
pISSN - 0741-5400
DOI - 10.1189/jlb.0305159
Subject(s) - biology , cd40 , virology , immunology , cancer research , microbiology and biotechnology , genetics , in vitro , cytotoxic t cell
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 sinaling 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.