German researchers have developed a monoclonal antibody (CAL2) that when used in immunohistochemical assays is a specific, sensitive, rapid, simple, and low-cost method of detecting CALRETICULIN (CALR) mutations.1

CALR mutations are a major driver in myeloproliferative neoplasms (MPNs) and are mainly associated with primary myelofibrosis (PMF) and essential thrombocytopenia (ET). Previously, they were only detectable by molecular assays, which were overly complicated and had limitatations.

Researchers developed a mouse hybridoma designated as CAL2 that secretes antibodies that selectively stain cells carrying mutated CALR proteins in routinely processed bone marrow paraffin sections.

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It was tested on 173 human specimens, including bone marrow samples consisting of myeloid and non-myeloid neoplasms and non-neoplastic samples.

The CAL2 monoclonal antibody was used to stain the MPNs, other bone marrow disease, and normal bone marrow. Results were consisted over repeated stainings. This method was compared with the Sanger sequencing and produced a 100% correlation.


  1. Stein H, Bob R, Durkip, Erck C, et al. A new monoclonal antibody (CAL2) detects CALRETICULIN mutations in formalin-fixed and paraffin-embedded bone marrow biopsies. [published online ahead of print August 14, 2015]. Leukemia. doi: 10.1038/leu.2015.192.