{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,7,30]],"date-time":"2025-07-30T16:03:23Z","timestamp":1753891403790,"version":"3.41.2"},"reference-count":28,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2022,6,16]],"date-time":"2022-06-16T00:00:00Z","timestamp":1655337600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Immunol."],"abstract":"<jats:p>The FcR for IgM (Fc\u00b5R) is the newest member of the FcR family, selectively expressed by lymphocytes, and distinct from FcRs for switched Ig isotypes that are expressed by various immune cell types and non-hematopoietic cells. From studies of <jats:italic>Fcmr<\/jats:italic>-ablated mice, Fc\u00b5R was shown to have a regulatory function in B-cell tolerance, as evidenced by high serum titers of autoantibodies of the IgM and IgG isotypes in mutant mice. In our previous studies, both cell-surface and serum Fc\u00b5R levels were elevated in patients with chronic lymphocytic leukemia (CLL), where antigen-independent self-ligation of BCR is a hallmark of the neoplastic B cells. This was assessed by sandwich ELISA using two different ectodomain-specific mAbs. To determine whether the serum Fc\u00b5R is derived from cleavage of its cell-surface receptor (shedding) or its alternative splicing to skip the transmembrane exon resulting in a 70-aa unique hydrophilic C-terminus (soluble), we developed a new mouse IgG1\u03ba mAb specific for human soluble Fc\u03bcR (solFc\u03bcR) by taking advantages of the unique nature of transductant stably producing His-tagged solFc\u00b5R and of an <jats:italic>in vivo<\/jats:italic> differential immunization. His-tagged solFc\u03bcR attached to exosomes and plasma membranes, allowing immunization and initial hybridoma screening without purification of solFc\u03bcR. Differential immunization with tolerogen (membrane Fc\u03bcR) and immunogen (solFc\u03bcR) also facilitated to generate solFc\u03bcR-specific hybridomas. The resultant solFc\u03bcR-specific mAb reacted with serum Fc\u00b5R in subsets of CLL patients. This mAb, along with another ectodomain-specific mAb, will be used for verifying the hypothesis that the production of solFc\u00b5R is the consequence of chronic stimulation of BCR.<\/jats:p>","DOI":"10.3389\/fimmu.2022.863895","type":"journal-article","created":{"date-parts":[[2022,6,16]],"date-time":"2022-06-16T12:54:50Z","timestamp":1655384090000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":2,"title":["Soluble Fc Receptor for IgM in Sera From Subsets of Patients With Chronic Lymphocytic Leukemia as Determined by a New Mouse Monoclonal Antibody"],"prefix":"10.3389","volume":"13","author":[{"given":"Pedram","family":"Mahmoudi Aliabadi","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ruth","family":"Teuber","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Peter 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