Homomultimeric structures of HLA-G. HLA-G molecules can form homomultimers through the generation of Cys42-Cys42 or Cys42-Cys147 disulphide bonds. Possible monomeric and multimeric structures are shown. Gray boxes indicate hypothetical structures that have not been reported: β₂m-free HLA-G1 or HLA-G5 homotrimers, HLA-G4 homodimers and homotrimers, and HLA-G3 or HLA-G7 homodimers. HLA-G2 or HLA-G6 homodimers have been reported but their generation through Cys42-Cys42 disulphide bonds has not, although it is likely. HLA-G2 or HLA-G6 and HLA-G3 or HLA-G7 homotrimers do not seem to be possible as these isoforms lack Cys147 of α2 domain, and the structure of HLA-G4 homotrimers is open to speculation.