Browsing by Author "Roberts, Joseph L"

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    Dominant Splice Site Mutations in PIK3R1 Cause Hyper IgM Syndrome, Lymphadenopathy and Short Stature.
    (J Clin Immunol, 2016-07) Petrovski, Slavé; Parrott, Roberta E; Roberts, Joseph L; Huang, Hongxiang; Yang, Jialong; Gorentla, Balachandra; Mousallem, Talal; Wang, Endi; Armstrong, Martin; McHale, Duncan; MacIver, Nancie J; Goldstein, David B; Zhong, Xiao-Ping; Buckley, Rebecca H
    The purpose of this research was to use next generation sequencing to identify mutations in patients with primary immunodeficiency diseases whose pathogenic gene mutations had not been identified. Remarkably, four unrelated patients were found by next generation sequencing to have the same heterozygous mutation in an essential donor splice site of PIK3R1 (NM_181523.2:c.1425 + 1G > A) found in three prior reports. All four had the Hyper IgM syndrome, lymphadenopathy and short stature, and one also had SHORT syndrome. They were investigated with in vitro immune studies, RT-PCR, and immunoblotting studies of the mutation's effect on mTOR pathway signaling. All patients had very low percentages of memory B cells and class-switched memory B cells and reduced numbers of naïve CD4+ and CD8+ T cells. RT-PCR confirmed the presence of both an abnormal 273 base-pair (bp) size and a normal 399 bp size band in the patient and only the normal band was present in the parents. Following anti-CD40 stimulation, patient's EBV-B cells displayed higher levels of S6 phosphorylation (mTOR complex 1 dependent event), Akt phosphorylation at serine 473 (mTOR complex 2 dependent event), and Akt phosphorylation at threonine 308 (PI3K/PDK1 dependent event) than controls, suggesting elevated mTOR signaling downstream of CD40. These observations suggest that amino acids 435-474 in PIK3R1 are important for its stability and also its ability to restrain PI3K activity. Deletion of Exon 11 leads to constitutive activation of PI3K signaling. This is the first report of this mutation and immunologic abnormalities in SHORT syndrome.
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    Partial splenectomy but not total splenectomy preserves immunoglobulin M memory B cells in mice.
    (Journal of pediatric surgery, 2011-09) Tracy, Elisabeth T; Haas, Karen M; Gentry, Tracy; Danko, Melissa; Roberts, Joseph L; Kurtzberg, Joanne; Rice, Henry E

    Purpose

    The mechanism by which partial splenectomy preserves splenic immune function is unknown. Immunoglobulin (Ig) M memory B cells are critical for the immune response against encapsulated bacteria and are reduced in asplenic patients, although it is unknown whether partial splenectomy can preserve memory B cells. We hypothesized that IgM memory B cells (murine B-1a cells) would be preserved after partial splenectomy but not after total splenectomy in mice.

    Methods

    We performed total splenectomy (n = 17), partial splenectomy (n = 10), or sham laparotomy (n = 16) on C57BL/6J mice. Mice were killed on postoperative day 10 or 30, and peritoneal washings were analyzed by multiparameter flow cytometry for expression of murine B-1a cells (IgM(pos)IgD(dull)CD5(pos)B220(dull)).

    Results

    We found that B-1a cells were significantly reduced after both total and partial splenectomies compared with sham laparotomy in the early postoperative period, although normal levels of B-1a cells returned by postoperative day 30 in mice undergoing partial splenectomy but not total splenectomy.

    Conclusion

    Partial splenectomy but not total splenectomy preserves the B-1a B-cell population in mice within 30 days after surgery. Maintenance of these critical B cells may contribute to the preservation of a splenic-dependent immune response after partial splenectomy.