The proposed program will encompass two main areas of investigation: 1. The structure of the various classes and subclasses of human immunoglobulins and their variants in an effort to relate this to their specific functional properties, their evolutionary origin and their genetic control. 2. Chemical and immunologic characterization of the two types of amyloid, their biosynthesis and mechanisms for their deposition and formation. BIBLIOGRAPHIC REFERENCES: Michaelsen, T., Frangione, B., Franklin, E.C. and Sletten, K.: Primary structure of chymotryptic fragment (Fh) corresponding to the "hinge" region of the human IgG3 subclass. Abstract. III European Meeting of Immunology, Copenhagen, August, 1976. Franklin, E.C., Frangione, B. and Prelli, F.: The defect in mu Heavy Chain Disease protein GLI. J. Immunol., 116:1194, 1976.