Soluble versions of heterodimeric receptors, e.g., CD94/NKG2 receptors, and methods of producing and using such constructs, are described. The constructs comprise soluble fragments of, each receptor monomer, and some constructs further comprise at least one immunoglobulin Fc domain. Exemplary constructs are those wherein (1) each soluble fragment is linked to an immunoglobulin Fc domain, which are then allowed to dimerize, (2) each soluble fragment is linked to an immunoglobulin Fc domain mutated to promote forced dimerization with the correct counterpart, and (3) single-chain constructs where the monomeric receptor fragments are linked, and the C-terminal fragment is linked to an Fc domain.