Article Sections

Introduction

Hyper-IgM syndrome is a primary immunodeficiency syndrome characterized by impaired immunoglobulin class switching.  Therefore, B cells continue to produce IgM, leading to decreased or absent serum IgG, IgA, or IgE.  Patients have recurrent infections and failure to thrive.

Pathogenesis

B-cell development begins in the bone marrow, where hematopoietic stem cells differentiate into immature B cells that migrate to peripheral lymphoid tissue (eg, spleen, lymph nodes) for maturation ( Figure 1).  Mature B cells are capable of producing IgM and IgD.  However, on exposure to antigens, mature B cells undergo a series of changes to become plasma cells, as follows:

  • In the absence of T-helper cells, most mature B cells differentiate into short-lived plasma cells that produce antigen-specific IgM.
  • In the presence of T-helper cells, most mature B cells differentiate into long-lived plasma cells that produce antigen-specific IgG, IgA, or IgE, as follows:

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Figures

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Tables

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