Interaction of alpha 1 with alpha 2 region in class I MHC proteins contributes determinants recognized by antibodies and cytotoxic T cells.
The structure-function relationship of individual coding regions of class I mouse major histocompatibility complex proteins was studied by a combination of recombinant DNA, gene transfer techniques, and serologic and functional characterization. To examine the role of alpha 1 and alpha 2 regions in antibody and CTL recognition, the third exon of H-2Dd, Kd, and Ld transplantation antigen genes was replaced by the homologous coding region of the Qa-2-coded class I gene, Q6. We have chosen to carry out the exon shuffling experiments between these two different types of class I genes, because they are structurally similar and did not evolve to carry out identical functions. Therefore, it is less likely that the hybrid proteins will fortuitously recreate alpha 1-alpha 2 controlled functionally important determinants. The replacement of H-2 alpha 2 coding region with its Q6 counterpart had different effects on the expression of the three genes. The mutant H-2Dd gene transfected into L cells was expressed at high levels and retained several of the serologic determinants found on parental H-2Dd and Q6 domains. The serologic epitopes on the mutant H-2Kd-transfected cells were detectable at very low levels, whereas the product of the mutant H-2Ld gene could not be identified at all. Analysis of cells transfected with mutant H-2Dd gene with alloreactive and minor antigen(s)-restricted cytotoxic T cells indicated that the hybrid proteins lost the ability to be recognized by T cells. Our data suggest that cytotoxic T cells recognize conformational determinants composed of amino acids from alpha 1 and alpha 2 regions. Alternatively, it could be proposed that T cell recognition sites located in a single alpha 1 or alpha 2 protein region are susceptible to distortion upon alpha 1-alpha 2 interactions. Such susceptibility to conformational changes of the amino-terminal domain of transplantation antigens could be of functional importance for H-2-restricted antigen presentation.
I
I
Stroynowski
S
S
Clark
L A
LA
Henderson
L
L
Hood
M
M
McMillan
J
J
Forman
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D004274:DNA, Recombinant; D000939:Epitopes; D006183:H-2 Antigens / Q000235:genetics / Q000276:immunology*; D006649:Histocompatibility Antigens / Q000235:genetics / Q000276:immunology*; D007739:L Cells; D046911:Macromolecular Substances; D008285:Major Histocompatibility Complex; D008565:Membrane Proteins / Q000276:immunology; D051379:Mice; D009154:Mutation; D011110:Polymorphism, Genetic; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*
D000911:Antibodies, Monoclonal; D004274:DNA, Recombinant; D000939:Epitopes; D006183:H-2 Antigens; D006649:Histocompatibility Antigens; D046911:Macromolecular Substances; D008565:Membrane Proteins