Original antigenic sin at the cellular level. II. Specificity of the antibodies produced by individual cells

Original antigenic sin has been studied at the cell level with mice given a primary injection of meta‐aminobenzoic acid (mB) (coupled to human IgG) and a secondary injection of meta‐sulfanilic acid (mS) (coupled to human IgG), or the reverse. Spleen cell activity against red cells coupled to these haptens was measured by the local hemolysis technique. In order to distinguish between mB specific cells, mS specific cells and cells forming antibodies to both, two procedures were developed: mB was added in the test medium in order to compete with anti‐mB antibodies and inhibit mB plaques. Two different types of red cells, pigeon and sheep red blood cells, were coated either with mB or with mS, providing a means of distinguishing three types of plaques: anti‐mS only, anti‐mB only and anti‐mS‐anti‐mB. Both procedures showed that cells specific for the primary hapten only are stimulated by the heterologous booster in the two reciprocal situations. These results are discussed in relation to the specificity of receptors and antibodies and to their affinities towards haptens.