Leukocyte immunoglobulin-like receptors: Novel innate receptors for human basophil activation and inhibition

Basophils, recruited from the blood to tissues, have been implicated by their presence in diverse allergic disorders including bronchial asthma, allergic rhinitis, and cutaneous contact hypersensitivity. We hypothesized that like other leukocytes involved in inflammatory responses, basophils would express members of the leukocyte immunoglobulin-like receptor (LIR) family of immunoregulatory molecules on their cell surface. We identified LIR7, an activating member coupled to the common Fc receptor gamma chain, and LIR3, an inhibitory member containing cytoplasmic immunoreceptor tyrosine-based inhibitory motifs, on these cells from human peripheral blood. Cross-linking of LIR7 resulted in the concentration-dependent net release of histamine (29.8 ± 10.8%) and cysteinyl leukotrienes (cysLTs) (31.4 ± 8.7 ng/10⁶ basophils) that were maximal at 30 minutes, and of interleukin-4 (IL-4) (410.2 ± 61.6 pg/10⁶ basophils) that was maximal at 4 hours and comparable with the response initiated by cross-linking of the high-affinity receptor for immunoglobulin E (FcεRI). Coligation of LIR3 to LIR7 or to FcεRI by means of a second monoclonal antibody significantly inhibited net histamine release, cysLT production, and IL-4 generation. That LIR3 is profoundly counterregulatory for both adaptive and innate receptors suggests a broad role in containment of the inflammatory response.