Induction of rat homocytotropic antibody against streptokinase-streptodornase (SK-SD) and specific neutralization of the antibody by low molecular weight component of SK-SD.

Homocytotrophic antibodies (HCA) were produced in rats by primary injection of streptokinase-streptodornase (SK-SD) after the antigen was absorbed on alminum hydroxide gel. The properties of rat SK-SD-specific HCA were qualitatively similar to SK-SD skin-sensitizing antibodies found in sera of human beings, namely, homocytotropic activity (48 h homologous PCA reaction), heat lability at 56 degrees C, and inactivation by reduction with 2-mercaptoethanol followed by alkylation with iodoacetamide. In neutralization tests, D-SK-SD, a low molecular hapten-like substance contained in SK-SD preparation, absorbed the antibody against ND-SK-SD antigen-specifically. The neutralizing activity mostly resided in fraction 1 of D-SK-SD separated through DEAE-Sephadex A-25 ion-exchange column, opposing the inhibitory activity of fraction 3 on lymphocyte transformation. The possible implication of these findings in the immunological treatment of streptococcal disorders is discussed.