Spontaneous release of cytotoxic alloantibody from viable cells sensitized in excess antibody.

When viable cells sensitized in excess cytotoxic alloantibody are washed and resuspended in antibody-free medium, they spontaneously release appreciable quantities of antibody. The amount released is directly proportional to the concentration of alloantibody during sensitization. Spontaneous release was observed from all cell types tested (thymocytes, lymphocytes, leukaemia cells and ascites sarcoma cells) and with all alloantibodies tested (H-2, θ and Ly-B). In preliminary tests with radio-labelled H-2 antibody, the quantity of antibody released in a period of 2½ hours was 29 per cent of the antibody originally absorbed. Dissociation at 37° was greater (or more rapid) than at 1°. When washed sensitized cells were suspended in antibody directed to an antigen closely adjacent on the cell surface to the site of attachment of the first antibody, release of the first antibody was impeded.