To establish the underlying cause of hyper-IgM syndrome in one female patient, B cell function was examined in response to CD40- and IL-4-mediated pathways. When CD40-induced functional responses were measured in unfractionated B cells, CD80 up-regulation, de novo Cμ-Cγ recombination, and Iγ transcription were all found to be relatively unaffected. However, CD40- and IL-4-mediated CD23 up-regulation and VDJ-Cγ transcription were clearly diminished compared to control cells. IL-4-induced CD23 expression was measurably reduced in the CD20− population as well. These results suggested that the patient’s defect is positioned downstream of CD40 contact and affects both CD40− and IL-4 signal transduction pathways. Further analysis of B cell function in CD19+ B cells revealed a clear B cell defect with respect to Iγ and mature VDJ-Cγ transcription and IgG expression. However, under the same conditions Iε transcription was relatively normal. Partial restoration of B cell function occurred if PBMC or CD19+ B cells were cultured in vitro in the presence of CD154 plus IL-4. Because addition of IL-4 to cocultures containing activated T cells failed to induce B cells to undergo differentiation, the ability of the patient’s B cells to acquire a responsive phenotype correlated with receiving a sustained signal through CD40. These findings support a model in which the patient expresses an intrinsic defect that is manifested in the failure of specific genes to become transcriptionally active in response to either CD154 or IL-4 and results in a functionally unresponsive B cell phenotype.

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.

Background: Inadequate titers of pneumococcal antibody (PA) are commonly present among patients with recurrent respiratory infections. Objective: We sought to determine the effect of the degree of inadequacy in baseline PA titers on the subsequent polysaccharide vaccine response, the incidence of sinusitis, and allergic conditions. Methods: A total of 313 patients aged 6 to 70 years with symptoms of recurrent respiratory infections were classified by baseline-pPA (percentage of protective [1.3 mg/mL] PA serotypes/total tested serotypes) and postvaccination pPA (post-pPA): Group A (adequate baseline-pPA), Group B (inadequate baseline-pPA, adequate post-pPA, responders), and Group C (inadequate baseline-pPA, inadequate postpPA, nonresponders, specific antibody deficiency [SAD]). Immunity against Streptococcus pneumoniae was defined as adequate when the pPA was 70%. Each group and combined groups, Group AB (inadequate baseline-pPA), and Group BC (adequate post-pPA) were analyzed for demographics, history of sinusitis, recurrent sinusitis in the following year, allergic conditions, and association with inadequate individual serotype titers. Results: Over 80% of patients with respiratory symptoms had inadequate baseline-pPA. Baseline-pPA and SAD prevalence are inversely related (odds ratio ¼ 2.02, 95% CI: 1.15-3.57, P ¼.01). Inadequate serotype 3 antibody titer is highly associated with SAD (odds ratio ¼ 2.02, 96% CI: 1.61-5.45, P <.01). The groups with inadequate pPA (Group B and C, or BC) had significantly higher percentage of patients with chronic rhinosinusitis (P <.001), allergic sensitization, and allergic rhinitis (P <.05). Group A contained higher percentage of patients with recurrent upper airway infections (P <.001). Conclusion: Low baseline-pPA and low antibody titers to serotype 3 are highly associated with SAD, increased incidence of respiratory infections including CRS and allergic conditions.