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Subthreshold desensitization of human basophils re‐capitulates the loss of Syk and F cε RI expression characterized by other methods of desensitization
Author(s) -
MacGlashan D.
Publication year - 2012
Publication title -
clinical and experimental allergy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.462
H-Index - 154
eISSN - 1365-2222
pISSN - 0954-7894
DOI - 10.1111/j.1365-2222.2012.04013.x
Subject(s) - syk , desensitization (medicine) , histamine , basophil , chemistry , immunoglobulin e , stimulation , receptor , pharmacology , endocrinology , immunology , microbiology and biotechnology , biology , biochemistry , tyrosine kinase , antibody
Background Clinical desensitization of patients to drugs involves progressive exposure to escalating doses of drug over a period of 24 h. In prior studies, this method was re‐capitulated in vitro to also demonstrate loss of mast cell or basophil responsiveness. However, most signalling studies of human basophils have identified changes in signalling by using other methods of inducing cellular desensitization. Objective This study examined two well‐described endpoints of basophil desensitization, loss of syk or Fcε RI expression, under conditions of subthreshold desensitization. Methods The loss of Fcε RI and syk was examined in human basophils. Results It was shown that both loss of syk and Fcε RI /IgE occurred during an escalating series of stimulation (anti‐IgE Ab) and that expression loss occurred despite the presence of little histamine release. If basophils were first cultured for 3 days in 10 ng/mL IL ‐3, the concentration‐dependence of histamine release shifted to 100‐fold lower concentrations of stimulus. However, loss of syk did not show any change in its EC 50 while loss of Fcε RI also shifted 100‐fold. From the perspective of early signal element activation, the marked shift in the EC 50 for histamine release was not accompanied by similar shifts in the EC 50s for several signalling elements. The EC 50s for phospho‐Src, phospho‐ SHIP 1, phospho‐Syk, or phospho‐Cbl did not change while the EC 50s for phospho‐Erk and the cytosolic calcium response did shift 100‐fold. Conclusions These studies show that under normal conditions, subthreshold desensitization leads to loss of two critical signalling molecules (Fcε RI and syk) but under at least one condition, treatment with IL ‐3, it is possible to markedly blunt the loss of syk, but not Fcε RI , while executing a proper subthreshold titration. These data also suggest that IL ‐3 modifies only the sensitivity of signalling elements that are downstream of syk activation.