SEROLOGICAL ANALYSIS OF THE DISSOCIATION PROCESS OF HLA-B AND HLA-C CLASS-I MOLECULES

Two forms of HLA class I molecules reacting differentially with the HC‐10 monoclonal antibody were identified at the surface of HLA‐A3, B7, Cw3 or Cw7 human cells. The HC‐10‐nonreactive form (which includes all HLA‐A3 and a large fraction of HLA‐B7, Cw3 and or Cw7 molecules) corresponds to heavy chains apparently tightly associated to β2‐microglobulin. The HC‐10‐reactive form (which represents only a fraction of cell surface expressed HLA‐B7, Cw3 and Cw7 molecules) corresponds to heavy chains loosely but still associated to β2‐microglobulin. Further biochemical analyses and the study of mouse transfected cells expressing other HLA class I specificities led to the following conclusions: (a) dissociation of HLA‐B and C molecules is a multistep phenomenon, the various stages being identifiable serologically; (b) acquisition of the HC‐10 antigenic determinant appears as a hallmark of HLA class I molecules engaged in the process of dissociation; however, its expression does not imply complete separation of heavy and light chains; (c) only the initial stage of the dissociation process can be identified on cell surfaces, whereas (d) following addition of detergent, dissociation of HLA‐B and C molecules spontaneously proceeds further, resulting in accumulation in cell lysate of cell surface‐derived isolated HLA‐B and C class I heavy chains. Copyright © 1990 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim