A case of primary immunodeficiency: hyper IgM syndrome

Hyper IgM syndrome are group to disorders characterized by elevated serum level of IgM and low or absent serum levels of IgG, IgA and IgE the mechanism of HIGM is immunoglobulin Class-Switch Recombination (CSR) failure and Somatic Hyper Mutation (SHM). This diagnosis should be considered in any patient presenting with hypogammaglobulinemia, with low or absent IgG and IgA and normal or elevated IgM level. In the present case report, this was a 6-year-old male child who had history of recurrent respiratory tract infections who presented with otitis media and persistent fever spikes. Immunoglobulin studies revealed a pattern consistent with hyper IgM.

Update on the pathogenesis of hyper IgM syndrome / 国际儿科学杂志

The hyper immunoglobulin M syndromes(HIGM) are a heterogeneous group of genetic disorders resulting in defects of immunoglobulin class switch recombination,with or without defects of somatic hypermutation.They can be classified as defects of signalling through CD40 causing combined immunodeficiency,or intrinsic defects in B cells of the mechanism of class switch recombination resulting in a pure humoral immunodeficiency.This review summarizes the molecular pathogenesis of HIGM.

Newly Identified TLR9 Stimulant, M6-395 Is a Potent Polyclonal Activator for Murine B Cells

BACKGROUND: Toll-like receptors (TLRs) have been extensively studied in recent years. However, functions of these molecules in murine B cell biology are largely unknown. A TLR4 stimulant, LPS is well known as a powerful polyclonal activator for murine B cells. METHODS: In this study, we explored the effect of a murine TLR9 stimulant, M6-395 (a synthetic CpG ODNs) on B cell proliferation and Ig production. RESULTS: First, M6-395 was much more potent than LPS in augmenting B cell proliferation. As for Ig expression, M6-395 facilitated the expression of both TGF-beta1-induced germ line transcript alpha (GLTalpha) and IL-4-induced GLTgamma1 as levels as those by LPS and Pam3CSK4 (TLR1/2 agonist) : a certain Ig GLT expression is regarded as an indicative of the corresponding isotype switching recombination. However, IgA and IgG1 secretion patterns were quite different--these Ig isotype secretions by M6-395 were much less than those by LPS and Pam3CSK4. Moreover, the increase of IgA and IgG1 production by LPS and Pam3CSK4 was virtually abrogated by M6-395. The same was true for the secretion of IgG3. We found that this unexpected phenomena provoked by M6-395 is attributed, at least in part, to its excessive mitogenic nature. CONCLUSION: Taken together, these results suggest that M6-395 can act as a murine polyclonal activator but its strong mitogenic activity is unfavorable to Ig isotype switching.

Activin A Stimulates Mouse APCs to Express BAFF via ALK4-Smad3 Pathway

BACKGROUND: B cell-activating factor belonging to the TNF family (BAFF) is primarily expressed by macrophages and dendritic cells, and stimulates B cell proliferation, differentiation, survival, and Ig production. In the present study, we explored the effect of activin A on BAFF expression by APCs. METHODS: To investigate the effect of activin A on BAFF expression by mouse APCs, we measured the level of BAFF expression at the transcriptional and protein levels using RT-PCR and ELISA. RESULTS: Activin A markedly enhanced BAFF expression in mouse macrophages and dendritic cells at both the transcriptional and protein levels. SB431542, an activin receptor-like kinase 4 (ALK4) inhibitor, completely abrogated activin A-induced BAFF transcription. Furthermore, overexpression of DN-Smad3 abolished activin-induced BAFF expression at the transcriptional and protein levels. CONCLUSION: These results demonstrate that activin A can enhance BAFF expression through ALK4-Smad3 pathway.

Comparison of class switch recombination assays for immunoglobulin synthesis

The second step of immunoglobulin gene alteration consists of somatic hypermutation and class switch recombination. 80th are regulated by activation-induced cytidine deaminase (AID). Methods: Study on possible application of class switch recombination assays for immunoglobulin gene alteration via AID. Cell based assays using AID B lymphocyte and NIH3T3 cell carrying switch substrate; gene transfer using retrovirus system; FACS analysis; PCR and ELISA. Results: DNA sequencing for S region and gamma1CT are the most sensitive and accurate assays. However, gamma1CT assay seemed to be more reliable and applicable. Others are accurate assays but less applicable. Conclusion: gamma1CT determination is the best class switch recombination assay for immunoglobulin gene alteration via AID.