In vivo arming of cutaneous mast cell receptors by IgE released from macrophages

Intracutaneous injection of purified peritoneal macrophages harvested from ovalbumin (OVA)-hypersensitive high-IgE-responder BN rats into naive animals sensitised the injection sites for subsequent OVA-specific passive cutaneous anaphylaxis (PCA) reactions. The underlying mechanism(s) were investigated using a macrophage cell line (WEHI 265.1), which exhibited comparable sensitising activity in rat or mouse skin, after initial pulsing in vitro with antiserum rich in OVA-specific IgE. Transfer of OVA-hypersensitivity by the cell line (1) was IgE-dependent and did not occur when the cells were pre-exposed to antiserum containing OVA-specific IgG alone, (2) was blockable by saturation of cell surface receptors in the recipient with myeloma IgE (but not myeloma IgG), and (3) did not occur in mast cell-deficient mice carrying the W/Wv mutation, in contrast to their normal heterozygous littermates which developed marked OVA-hypersensitivity at the injection site. These results are consistent with arming of IgE-receptors on cutaneous mast cells by IgE antibody released from macrophages, and hint at a possible role for phagocytes in amplifying IgE-mediated reactions in tissues.