Inverse association between IgG–anti-κ autoantibody and CA in noninfection patients with anti-I and anti-i autoantibodies. In patients with cold agglutination of noninfectious origin caused by (A) anti-I (n = 128), (B) anti-i (n = 16), and (C) anti-Pr (n = 22) autoantibody, the titers of IgG–anti-κ and CA were determined (left and right ordinate). Sera with identical CA titers were included into the same group (abscissa). Anti-κ titers are given in OD 405 nm (median ± MAD).