Binding of surface IgG by immunocompetent thymus cells

Area of Science:

• Immunology
• Cell Biology

Background:

• Immunoglobulin (Ig) can facilitate in vitro alloantigen recognition by immunocompetent thymus cells.
• Surface immunoglobulins (sIg) are present on B lymphocytes.

Purpose of the Study:

• To investigate the binding of surface immunoglobulins to immunocompetent thymus cells.
• To determine the role of immunoglobulin binding in alloantigen recognition.

Main Methods:

• Isolation of surface immunoglobulins from radiolabeled splenic B lymphocytes.
• In vitro binding assays of solubilized immunoglobulins to lymphoid cells, especially thymus cells.
• Analysis of preferential binding of IgG and its fragments (Fc) to subset-I thymocytes.

Main Results:

• Solubilized surface immunoglobulins bind to lymphoid cells, with preferential binding to immunocompetent thymus cells.
• Subset-I thymocytes show preferential binding of IgG over IgM.
• Subset-I thymocytes preferentially bind the Fc piece of IgG after papain digestion.

Conclusions:

• Surface immunoglobulins, particularly IgG, bind to immunocompetent thymus cells.
• The Fc portion of IgG is preferentially bound by subset-I thymocytes.
• While not directly activating cells, IgG binding is demonstrated to play a role in in vitro alloantigen recognition.