HLA variants of cultured human lymphoid cells: evidence for mutational origin and estimation of mutation rate.

Variants of a diploid lymphoid cell line that show a loss of HLA-B27 antigen occur randomly in time and independently of exposure to the alloantiserum used for their isolation. From these and previous findings of variant stability, inducibility by mutagens, and the absence of linked variation, we colclude that most HLA variants arise by mutation. The mutation rate for HLA-B27 loss is 8 x 10(-7) per cell per generation.