Description of a mouse monoclonal anti-HLA-B27 antibody HLA-ABC-m3

The production and characterization of a new anti-HLA-B27 monoclonal antibody HLA-ABC-m3 is described. This cytotoxic IgG2a antibody binds protein A and is able to precipitate cell surface molecules of 43,000 and 12,000 daltons corresponding to the HLA heavy chain and β2-microglobulin. Population testing revealed that the HLA-ABC-m3 antibody reacted with the peripheral blood lymphocytes of 47/47 individuals conventionally typed as HLA-B27⁺ and with 5/105 HLA-B27⁻ individuals. These five extra reactions were with individuals expressing the cross-reactive HLA-B7 alloantigen, although the affinity of the monoclonal antibody for B27 heterozygous individuals (approx 10⁹ M⁻¹) was tenfold greater than with B7 individuals (approx 10⁸ M⁻¹). In addition, HLA-ABC-m3 reactivity segregated with HLA-B27 in two families. This monoclonal antibody should be of value in the investigation of the role of HLA-B27 in disease.