Abstracts of Papers Presented at the Third International Complement Workshop, Harvard Medical School, Boston, Massachusetts, June 3–5, 1968 Complement-Dependent Lysosomal Activation

Embryonic chick bones grown in organ culture in a medium containing rabbit antibody against cell membrane antigens and rabbit complement show extensive degradation of cartilage matrix and characteristic resorption of bone. Biochemical studies have shown that these changes are due to release of lysosomal protease. Cell death is confined to the extreme outer layer of cells; and if the affected rudiment is returned to a normal medium, recovery occurs rapidly and may be associated with irregular growth. These changes are wholly dependent on the presence of complement and are abolished if the source of complement is heated, or treated with antigen-antibody complexes or with zymosan. Serum from C′6-deficient rabbits is also quite inactive. Immunohistochemical examination of affected rudiments shows that fixed rabbit γ globulin is found maximally at the periphery of the rudiment and decreases sharply towards the center. Fixed C′3 is apparently confined wholly to the most peripheral layers.