Gastrointestinal defects and immunodeficiency syndrome with normal in vitro IgG production

Abstract

Background: Gastrointestinal defects and immunodeficiency syndrome (GIDID) is a severe neonatal disorder usually fatal within the first months of life. We report a case presenting with intestinal atresia, combined immunodeficiency, and a novel association with hypothyroidism and cardiac malformations. The immune phenotype was remarkable for agammaglobulinemia, lymphopenia, and mildly decreased lymphocyte proliferation. We present here the unique phenotype as well as studies to determine if the agammaglobulinemia was due to an intrinsic B lymphocyte defect. Methods: Peripheral blood mononuclear cells from the patient and a healthy control were isolated by Ficoll-Hypaque centrifugation and stimulated with anti-CD40, IL-4 and IL-21 for 7 days. Total IgG production was measured by ELISA in the supernatant of the stimulated sample on day 7. Cells were stained for CD19, CD27, IgM, CD11b, CD11c, and CD14. Results: At day 7, supernatant from the patient stimulated cells contained levels of total IgG comparable to the control (755 ng/mL vs. 658 ng/mL, respectively). B cell maturation appeared impaired, as morphologically the patient sample demonstrated fewer B cell clones and cells with dendritic projections. Conclusions: Despite this typical severe clinical picture of GIDID with agammaglobulinemia, IgG production was detected under optimal stimulation for induction of plasma cells. This suggests that there may not be an inherent defect in class switching and antibody production in B cells in this disorder. It is possible that the in vivo physical or cytokine milieu may be defective for optimal B cell function. Further studies assessing the function of the immune cells as well as possible gastrointestinal loss of immunoglobulins are needed in this disease. Statement of novelty: Despite much improvement in understanding the effects of TTC7A mutations in GIDID, the root cause of hypogammaglobulinemia in these patients is still unclear. The work portrayed in this study furthers the current knowledge. It suggests that when appropriately stimulated in vitro, this patient’s B cells were capable of adequate immunoglobulin production. Moreover, to the best of our knowledge, this patient is the first with this genetic defect to be reported with hypothyroidism and cardiac malformations.