Anti–HLA-Ib antibody reactivity (expressed as MFI) in the sera of normal nonalloimmunized males and healthy females. These sera were obtained from normal volunteers from Mexico. The sera are identified with Alb numbers. The corresponding HLA-Ia reactivity for the sera of nonalloimmunized males was reported elsewhere.^9(Fig3) White box, MFI <500; light gray box, MFI 500-999; medium gray box, MFI 1000-1999; dark gray box, MFI 2000-4999.