Transfected human class I gene product adequately assembles minor histocompatibility antigens

The success of HLA genotypically identical bone marrow grafting is still hampered by graft vs host disease and rejection of the graft. One of the causes of the latter complication could be attributed to minor histocompatibility (miH) antigen disparities between HLA genotypically identical siblings (Goulmy 1988). In previous in vitro studies, we demonstrated the presence of anti-host cytotoxic Τ cell (CTL) as well as proliferative (Th) Τ cell reactions in blood-samples taken after HLA identical bone marrow transplantation (van Eis 1990a, b). The latter activities are directed against miH antigens which are recognized in association with MHC class I (CTL) and class II (Th) products (Goulmy 1988; van Eis 1990c). We recently acquired CTL clones specific for five non-sexlinked miH antigens designated HA-1, -2, -3, -4, and -5, whereby HA-1, -2,-4, and -5 use the HLA-A2 gene product as restriction molecule. Using the latter CTL clones, immunogenetic studies were carried out to determine the miH antigen gene frequencies and to study the miH antigen segregation patterns in families. One complication in these studies is that it is necessary for the HLA-A2 molecule to be present in order to detect the miH antigens. As illustrated in Figure la, the HLA-A2 positive identical siblings 02 and 03 carry miH antigens HA-1 and -2. Since the father (01) of family Β oriy posseses HA-2, the miH antigen HA-1 must have been inherited from the mother. Therefore, the absence of the required MHC class IHLAA2 restricting antigen hampers adequate genetic analysis in this and other families. In order to solve this deficit, we used electroporation (Potter et al. 1984) to introduce cloned HLA genes into the Epstein-Barr transformed Β cell lines of selected members of this family. We transfected the HLA-A2 gene cloned in the pHEBO vector (Sugden et al. 1985; Shimizu et al. 1986) into the HLA-A2 negative cells of the mother