HLA-C and psoriasis: Second, linkage disequilibrium with C*06:02 does not explain the lower frequency of the HIV-1 progression allele B*35 in psoriasis, nor can it account for the concordance of amino acid residues at HLA-B positions 67, 70, and 97 whose association with psoriasis was shown to be independent of HLA-B*57:01 and HLA-C*06:02 (Cys67, Ser67, Lys70, Asn97, Arg97, see Figure 1.