Identification of alloantisera reacting with HLA-C blank (Cx52) using a mouse L-cell transfected with the HLA-Cw*1201 allele.

The HLA-C locus frequently has a serologically undefined "blank" (CwBL) specificity. A cDNA clone derived from the HLA-C gene with a blank specificity (Cx52) strongly associated with the most common haplotype in a Japanese population, A24-CwBL-B52-DR2-DQ6-DP9, has been recently cloned and sequenced in our laboratory and officially designated Cw1201 as an allelic name, indicating that the inability to define the HLA-C antigen serologically in this haplotype is not due to an HLA-C antigen gene deletion or mutation, but to the absence of typing sera. In this paper, a mouse L-cell transfectant expressing this Cw1201 gene product was constructed and employed for screening of alloantisera recognizing the HLA-C antigen with the Cw1201 specificity. Two alloantisera against Cw1201 were thus identified and characterized using HLA homozygous B-cell lines and local panel PBL cells, indicating that a transfectant expressing a single HLA provides an efficient screening system for collection of HLA-typing sera, especially reacting with serologically unclassifiable "blank" antigens.