The detection of Ia antibodies in polyspecific H-2 alloantisera absorbed with erythrocytes.

H-2 alloantisera contain Ia antibodies whose detection is obscured by the presence of serodominant K,D specificities. A method is described whereby Ia antisera can be prepared by absorbing conventional H-2 sera with donor-strain erythrocytes. The analysis of such absorbed antisera has led to the identification of the new specificity Ia.16, and the redefinition of the specificities H-2.34 and H-2.46 as complex Ia specificities which map in the I-A region of the H-2 complex. A number of other so-called H-2 specificities also appear to have Ia-like properties.