Interleukin 2 induces T cell-dependent IgM production in human B cells

Area of Science:

• Immunology
• Cell Biology

Background:

• Mononuclear cells produce IgM, a key antibody in the immune response.
• Interleukin 2 (IL 2) is a cytokine involved in immune regulation.

Purpose of the Study:

• To identify the factor(s) in conditioned medium responsible for stimulating IgM production.
• To elucidate the role of IL 2 in B cell activation and differentiation.

Main Methods:

• Activation of human mononuclear cells with concanavalin A and phorbol myristate.
• Partial purification of conditioned medium using gel filtration and chromatofocusing.
• Experiments with purified and recombinant IL 2.
• B cell differentiation assays in the presence and absence of T cells.

Main Results:

• Conditioned medium strongly stimulated in vitro IgM production.
• The IgM-stimulating activity co-eluted with IL 2, and further purification confirmed IL 2 as the responsible factor.
• Purified and recombinant IL 2 induced IgM production, but required T cells for indirect B cell activation.
• A distinct factor, separate from IL 2, was found to differentiate B lymphocytes into IgM-producing cells without T cells.

Conclusions:

• IL 2 plays a role in inducing IgM production, likely indirectly through T cell activation.
• A novel, IL 2-independent factor exists that can directly differentiate human B lymphocytes into IgM-producing cells.