We report the production and application of a recombinant IgCw molecule, which is composed of only the constant domains of the heavy (C-H) and light (C-L) chains, lacking a variable (V) domain. We produced IgCw, especially human IgCw-gamma kappa (98 kDa), composed of two human C gamma chains (37 kDa each) and two C kappa chains (12 kDa each), using HEK293F cell culture. We found that the yield of IgCw-gamma kappa protein was similar to 20 mg/L, which was comparable to that of full-size IgG; it bound to Fc gamma receptor-positive cells with a low background noise on Fc gamma receptor-negative cells; and IgCw-gamma kappa can be used as a reference for measurement of Ig concentration. Moreover, C gamma and C kappa chains were easily isolated from IgCw-gamma kappa by a single step of affinity chromatography in the presence of a reducing agent. These results demonstrate that the IgCw molecule has the potential to be used for certain in vitro and in vivo applications as an alternative to an irrelevant isotype control IgG, and to be used a favorable antigen for acquiring isotype-specific antibodies by immunizing animals. (C) 2019 The Authors. Published by Elsevier Inc.