Class I H‐2D^b determinants are not involved in hybrid resistance to parental H‐2^b/Hh‐1^b bone marrow allograft

Abstract

Hybrid resistance to parental H-2b bone marrow grafts is directed to a cell surface structure controlled by the Hh-1 locus in or near the H-2D region. The nature of this surface structure is not known. Since homozygosity at the class I H-2D locus or loci in this haplotype would seem a necessary but not sufficient condition for the grafts' susceptibility to resistance, we tested whether the expression of this phenotype is dependent on the expression of class I H-2Db determinants. Cloned variants of H-2b tumor RBL-5 were obtained by immunoselection for the absence of H-2Db expression, as determined by the inability to bind specific antibody and to induce or react with alloreactive cytotoxic T lymphocytes. The three clones used in this study were H-2Db negative but H-2Kb positive and were natural killer cell resistant. When tested in vivo as competitive inhibitors the variant cells were capable of blocking hybrid resistance to parental H-2b bone marrow grafts as were unselected H-2Db-positive parental line cells. Therefore, H-2Db expression is irrelevant for Hh-1b expression. An incidental observation was that YAC-1 cells, a non-H-2b tumor with pronounced susceptibility to natural killing, were able to block hybrid resistance. This reactivity, not observed in our previous studies, raises the possibility that at least some of the effector cells are cross-reactive or capable of dual recognition.

Homopoietic histocompatibility (Hh-1) phenotype and the regulation of its expression

“…Their observations share certain features with autoreactive F 1 antiparent CTLs induced in vitro (Nakano et al 1981;Nakamura and Cudkowicz 1982). However, the properties of these CTLs clearly differ from those of HR in several important aspects, including the CTLs' specificity for class I molecules and the lack of such specificity in HR (Daley et al 1987;Milisauskas et al 1987;). …”

“…Hybridoma 16-1-11N (Ozato et al 1980) secreting H-2Kk-specific antibody was obtained from the American Type Culture Collection (Rockville, MD). Binding ofmAb to the cell surface was detected in a two-step assay with 125I-labeled sheep anti-mouse IgG (Amersham, Arlington Heights, IL), as described (Milisauskas et al 1987).…”

“…A standard 4 h 5~Cr-release assay was used, employing YAC-1 as target cells, and splenocytes from B6C3F 1 mice as effector cells, as described (Milisauskas et al 1987). B6C3F 1 mice were either untreated or injected i.p.…”

“…In vitro generation of ailoreactive CTLs and the 4 h 51Cr-release assay were as described (Milisauskas et al 1987).…”

“…The Hh-1 locus is closely linked to the H-2D region, and has been mapped to the H-2S/H-2D interval through analysis of intra-H-2 recombinants (Daley et al 1987;Rembecki et al 1987a). Analysis of mutant H-2 haplotypes and variant cell clones indicates that the H-2D class I gene products are not relevant for the expression or recognition of the Hh-1 locuscontrolled structures (Daley et al 1987;Milisauskas et al 1987;Milisauskas and Nakamura 1988).…”