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Immunoglobulin A (IgA) polymerization sites in human immunocytes: immunoelectron microscopic study

I Moro1, T Iwase, K Komiyama

  • 1Department of Pathology, Nihon University School of Dentistry, Tokyo, Japan.

Cell Structure and Function
|April 1, 1990
PubMed

Insights

Polymeric IgA polymerization and joining chain addition occur in the perinuclear space and endoplasmic reticulum of human lymphocytes before secretion. This process is crucial for immunoglobulin function.

Area of Science:

  • Immunology
  • Cell Biology
  • Molecular Biology

Background:

  • Secretory component (SC) plays a role in immunoglobulin A (IgA) transport.
  • The joining (J) chain is essential for the polymerization of IgA and IgM.

Purpose of the Study:

  • To determine the ultrastructural sites of human IgA polymerization.
  • To investigate the cytoplasmic affinity of polymeric IgA for SC and J chain expression in lymphocytes.

Main Methods:

  • Pokeweed mitogen (PWM)-stimulated human peripheral blood lymphocytes (PBL) were cultured.
  • Immunoelectron microscopy was used to examine SC-binding, IgA, and J chain expression.
  • Flow cytometry was used to quantify SC-binding and J chain positive cells.

Main Results:

  • SC-binding was observed in 5.7% of transformed PBL, primarily in IgA-producing cells.
  • A high proportion of IgA- and IgM-producing cells expressed intracellular J chain.
  • Immunoelectron microscopy revealed IgA polymerization and J chain addition in the perinuclear space and endoplasmic reticulum.

Conclusions:

  • IgA polymerization and J chain addition occur in the perinuclear space and endoplasmic reticulum.
  • These events precede the secretion of immunoglobulins.
  • The findings provide ultrastructural insights into the synthesis of polymeric IgA.

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