Essential Role of Monocytes in theIn VitroProduction of IL-4 and Nonspecific IgE Antibody by Peripheral Blood Lymphocytes from Mice Sensitized s.c. Once with Cedar Pollen

Abstract

To explore which cytokine or cell is essential for the production of antibodies (Abs) of the IgE class in allergic diseases, we injected cedar pollen into wild-type, interferon-gamma(-/-) (IFN-gamma(/)), or interleukin-4(-/-) (IL-4(-/-)) BALB/c mice through four (i.n., i.p., s.c., and i.v.) different routes without adjuvant. Wild-type or IFN-gamma(-/-), but not IL-4(-/-), mice sensitized once or twice showed a significant increase in total IgE Ab in their serum, revealing the essential role of IL-4 in the production of total IgE Ab. We separated peripheral blood mononuclear cells (PBMCs) from untreated or sensitized mice into monocyte-rich, lymphocyte-rich, and granulocyterich populations by Percoll density-gradient centrifugation or into specific antigen cells by flow cytometry, cultured the cells in various combinations, and examined the levels of cytokines and IgE Ab released into the medium. The PBMCs from mice sensitized s.c. once, but not those from untreated animals, produced significant amounts of IL-4 and total IgE Ab, whereas the lymphocyte-rich population alone did not. Unexpectedly, IL-4 and IgE Ab production was restored by the addition of Mac-1(+) cells in the monocyte-rich fraction to the lymphocyte-rich fraction. These results indicate the essential role of monocytes in the production of IL-4 and total IgE Ab by lymphocytes during the initial stage of sensitization.

IL‐4‐dependent induction of IgE+ basophils in peripheral blood and IgE+ B cells in spleen as respective indicators of allergen sensitization and a precursor of cells secreting allergen‐specific IgE antibody

“…These results reveal that the effects of 1–3 injections of cedar pollen on the number of IgE + cells in the peripheral blood of wild‐type, IFN‐γ ‐/‐, and IL‐4 ‐/‐ BALB/c mice are similar to those on the concentration of serum IgE Ab (14, 15), and suggest that the number of IgE + cells (or the amount of IgE on IgE + cells) might be a sensitive indicator of sensitization with allergen.…”

“…+ s.c.; 0.01 ± 0%, n = 3) injections of the allergen, implying that these organs might not be the place for presentation of allergic antigen. These results suggest that time‐dependent changes in IgE + cells in the spleen correlate with those of the concentrations of total IgE Ab in the serum (14, 15), and that the spleen might be specifically responsive to i.v.‐ injected allergen. In IL‐4 ‐/‐ BALB/c mice, IgE + cells in the blood and spleen were not detectable in the basal state; and all routes of injection of allergen both once and twice had no effect on the number of IgE + cells in the spleen, indicating the essential role of IL‐4 in the induction of IgE + cells in the spleen.…”

“…Whereas total IgE Ab was not enhanced significantly in the serum after an s.c. or i.v. injection of cedar pollen (14, 15), there was a significant increase in the number of IgE + cells in the peripheral blood, suggesting that the percentage of IgE + cells in the peripheral blood is a sensitive indicator of allergen sensitization.…”

“…Previously, we have shown that an increase in the production of total IgE Ab without a change in the IgA, IgG or IgM concentration is a prerequisite for the production of allergen‐specific IgE Abs (14) and that Mac‐1 + cells are essential for IL‐4 and total IgE Ab production by lymphocytes (15). In the present study, we reveal that time‐dependent changes in the number of IgE + cells (i.e.…”

“…or i.p., (but not i.v. or s.c.), injection of cedar pollen extract; and one or two more s.c. injections of the same allergen into i.n.‐, i.p.‐, i.v.‐ or s.c.‐ allergen‐sensitized mice induce specific IgE Ab production (14, 15). These results indicate that production of total IgE Ab without a change in the IgA, IgG or IgM concentration is a prerequisite for the production of allergen‐specific IgE Abs.…”