Modulatory role of intravenous gammaglobulin (IgIV) on the in vitro antibody response to a pneumococcal polysaccharide antigen.

INTRODUCTION: Clinical observations in patients with specific antibody deficiency treated for periods of time with IgG infusion have suggested that IgG may have a positive immunoregulatory effect on the production of specific antibodies against pneumococcal polysaccharides. We developed an in vitro model to test the effect of an IgIV preparation on the antibody production in response to a pneumococcal polysaccharide serotype and on the antibody and cytokine production in response to both a protein antigen and a pneumococcal polysaccharide antigen. METHODS: We studied 37 consecutive patients referred to our clinics for evaluation of their recurrent respiratory infections. Subjects were divided into two groups: 22 patients without SAD and 15 patients with SAD. PBMCs were left unstimulated or were stimulated with tetanus toxoid or pneumococcal polysaccharide serotype 19, in the presence of human albumin or IgIV. IgG anti-Pn-19 antibody, IL-4 and IFN-γ concentrations in culture supernatants were determined by ELISA. RESULTS: An increase in IgG anti-Pn-19 antibodies, associated with an increase in IFN-γ and a decrease in IL-4 production was observed in cultures stimulated with pneumococcal polysaccharide in the presence of IgIV when patients were analyzed together. The enhancing effect of IgIV was more significant for both IgG anti-Pn19 antibodies and IFN-γ in patients without SAD. In contrast, IgIV caused a significant decrease in IL-4 secretion in patients with SAD, which was associated with an increase in IgG anti-Pn19 antibodies in 3 of 7 of these patients. CONCLUSIONS: These results suggest that IgIV has some immunomodulatory effect on the in vitro production of IgG anti-Pn19 antibodies and cytokine production in cell cultures stimulated with Pn-19 antigen and that this modulation may be associated with a Th1/Th2 regulatory mechanism. Further studies at a cellular and molecular level are in progress to examine if the differences in the in vitro modulatory response to IgIV in these two groups of patients may point to a functional defect in patients with SAD.

Recurrent respiratory infections, specific antibody deficiencies, and memory B cells.

OBJECTIVES: To investigate the immunological phenotypes detected in children with recurrent upper and lower respiratory infections that have normal total immunoglobulin concentrations. METHODS: A cohort of over 60 children with recurrent respiration infections was evaluated for specific antibody deficiencies (SAD) and for memory B-cell abnormalities. A control group of children without recurrent infections was also evaluated. Evaluation included a detailed history of immunizations with pneumococcal vaccines; determination of IgM, IgG, IgA, and IgE concentrations; measurement of anti-pneumococcal polysaccharide antibody levels by ELISA and expression of CD27, IgD, and IgM on peripheral CD19(+)B cells by flow cytometry to determine the proportions of naive, IgM-memory B cells, and class-switched memory B cells. RESULTS: Patients were classified as having a SAD to either pure polysaccharides (PPV-SAD) or to conjugate polysaccharides (PCV-SAD) based on the number of polysaccharides to which they developed an adequate antibody response. A normal response to only 2 or fewer of 7 PCV or PPV serotypes was considered as evidence of SAD. Forty-one patients without SAD and 26 with SAD were identified. IgM-memory B cells were low in 3 of 41 patients without SAD; in 3 of 5 PPV-SAD patients; and in 10 of 21 PCV-SAD patients. Class-switched memory B cells were low in 19 of 41 patients without SAD; in all 5 patients with PPV-SAD; and in 11 of 21PCV-SAD patients. CONCLUSIONS: Patients with recurrent infection with or without SAD may have low IgM- and/or class-switched memory B cells. Ongoing research aims to determine the prognostic implications of these differences in patients with SAD.

Effect of L-arginine supplementation on immune responsiveness in patients with sickle cell disease.

BACKGROUND: L-arginine (L-Arg) is deficient in sickle cell disease (SSD) during vasoocclusion. We investigated possible causal relationship between L-Arg deficiency and immune dysfunction in SSD in steady-state. PROCEDURE: Fifteen patients with SSD in steady-state and 13 controls were studied. Plasma L-Arg levels were measured using liquid chromatography. T cell subsets and CD3zeta (CD3zeta) chain expression were analyzed using flow cytometry. Lymphocyte proliferative response to phytohemagglutinin (PHA) and production of IL-6 and interferon-gamma (IFN-gamma) were evaluated with and without L-Arg. RESULTS: SSD patients had significantly lower L-Arg levels than controls. CD3 and CD19 cell populations were comparable for both groups, but SSD patients had above normal numbers of natural killer cells (P = 0.06). Patients and controls exhibited significantly increased lymphocyte blastogenesis to PHA after introduction of L-Arg to cultures; response of patients was significantly greater than values for control individuals. Proliferative response to candida in SSD patients was significantly lower than in controls; L-Arg supplementation did not increase this response. L-Arg had no effect on blastogenic response to PPD and candida albicans. No effect was likewise seen in production of IL-6 and IFN-gamma after addition of L-Arg. CD3zeta chain expression increased after addition of L-Arg in both groups; differences were insignificant. CONCLUSION: L-Arg levels in steady-state SSD are significantly lower than in controls. L-Arg supplementation enhanced lymphocyte blastogenesis to PHA for both controls and patients, but not in response to antigen. There were no significant differences in CD3zeta chain expression although upregulation of expression occurred after L-Arg supplementation for both groups.