The following studies will be continued: a) On a novel concept, that an antibody, such as antirenin, acts as an enzyme in the irreversible inactivation of the antigen (renin). b) On the release of antirenin stored in tissues, into the circulation, due to an abrupt fall of blood pressure caused by anaphylactic shock or by vasodepressor agents. An investigation of the possible inhibition or inactivation of human renin by various drugs known to be potent inhibitors of enzymes. In an 8-step procedure, we have purified human renin 600-fold, but it still appears to be bound as a complex to other proteins, which has, until now, prevented all attempts at further fractionation and purification. as a next step we intend, therefore, to subject this "complex" to one or more of six procedures which are known to induce separation, solubilization, and dissociation of other enzymes or proteins into smaller subunits.