Transforming growth factor beta specifically enhances IgA production by lipopolysaccharide-stimulated murine B lymphocytes.

The addition of TGF-beta to cultures of LPS-stimulated murine B cells causes a approximately 10-fold enhancement of IgA production, yet causes a 10-fold decrease in total Ig production. IL-2 and, to a lesser extent, IL-5 synergize with TGF-beta to further enhance IgA production and partially reverse the inhibition of total Ig production. IgA constitutes only approximately 0.1% of total Ig in LPS-stimulated cultures, but that percentage rises to 15-25% in cultures to which TGF-beta and IL-2 are added. TGF-beta induces a substantial increase in IgA production from sIgA- B cells but inhibits IgA production by sIgA+ cells. This finding suggests that TGF-beta acts as an isotype-specific switch factor for IgA.

The characterization of four monoclonal antibodies specific for mouse IL-5 and development of mouse and human IL-5 enzyme-linked immunosorbent.

Four rat mAb directed against mouse IL-5 have been characterized by their ability to remove and neutralize mouse IL-5 activity in various bioassays. All four mAb absorbed IL-5 activity from solution. Although all were able to neutralize mouse IL-5 bioactivity, two were significantly more effective. These two were also able to neutralize the activity of mouse IL-5 delivered to B cells during a cognate-linked interaction with a Th cell clone. A two-site sandwich ELISA specific for mouse IL-5 was developed by using pairs of mAb. The mouse IL-5 ELISA is capable of detecting natural or mouse rIL-5 in supernatants, crude bacterial lysates, and high concentrations of mouse serum, and has a detection limit of less than 20 pg. Two of these antibodies cross-reacted with and neutralized human rIL-5, and one of these was used for development of an ELISA for human IL-5.

A mouse T cell product that preferentially enhances IgA production. I. Biologic characterization.

Supernatants from a subset of helper T cell clones can enhance IgA, IgE, and IgG1 production in cultures of lipopolysaccharide-stimulated, T cell-depleted spleen cells. The lymphokine interleukin (IL)-4 has been shown to cause the IgE and IgG1 enhancement produced by these supernatants. IgA enhancement, however, is mediated by a factor distinct from IL-4, although IL-4 can potentiate the effect of the IgA-enhancing factor. IgA-enhancing factor is also distinct from IL-1, IL-2, IL-3, granulocyte-macrophage colony-stimulating factor, and interferon-gamma and acts directly on B cells. Purified IgA-enhancing factor enhances IgA production three- to sixfold yet causes less than a twofold increase in other isotypes. The IgA enhancing activity is not inhibited by concentrations of interferon-gamma that inhibit IL-4 activities. In the accompanying article, we show that this IgA enhancing activity is a novel property of the lymphokine IL-5.

A mouse T cell product that preferentially enhances IgA production. II. Physicochemical characterization.

Certain subsets of helper T cells, following stimulation with concanavalin A, secrete factors that specifically enhance the production of IgG1, IgE, and IgA by lipopolysaccharide-stimulated B cells. In the previous report, we describe a factor from the helper T cell line MB2-1 which enhances IgA production. IgA-enhancing factor has been purified from serum-free supernatants of this cell line. The purified lymphokine is a family of microheterogeneous polypeptides presumably modified post-translationally. IgA-enhancing factor has a native m.w. of 45,000 to 60,000 with subunits of between 24,000 and 28,000 under reducing conditions. Upon Edman degradation, a single amino-terminal sequence is detected which is identical to that of the lymphokine interleukin 5. IgA-enhancing factor activity is thus mediated by the same polypeptide that has been characterized as type II B cell growth factor, T cell-replacing factor, and eosinophil-differentiation factor.

Isolation and characterization of lymphokine cDNA clones encoding mouse and human IgA-enhancing factor and eosinophil colony-stimulating factor activities: relationship to interleukin 5.

Conditioned medium from the Con A-treated mouse helper T-cell clone Ly1+2-/9 contains activities that enhance the production of IgA by mouse B cells and induce human cord blood cells to form eosinophil colonies. We have isolated a cDNA sequence that expresses IgA-enhancing factor and eosinophil colony-stimulating factor activities from a cDNA library prepared from activated Ly1+2-/9 cells. Based on homology with the mouse cDNA sequence, a human cDNA sequence coding for an interleukin with IgA-enhancing factor and eosinophil colony-stimulating factor activities was isolated from a cDNA library prepared from a human T-cell clone stimulated with anti-T3 antibody and phorbol 12-myristate 13-acetate. DNA sequence analyses revealed that mouse and human cDNA clones encode proteins of 133 and 134 amino acids, respectively, that are identical to cDNA clones encoding the T-cell replacing factor I and B-cell growth factor II activities. These results establish that a single cDNA clone encodes a protein that acts as a growth and differentiation factor for both B cells and eosinophils.