Immune lysis of liposomes and erythrocyte ghosts loaded with spin label.

It is shown that the paramagnetic resonance of spin labels offers a convenient technique for monitoring the complement-mediated immune lysis of erythrocyte ghosts, and sensitized phospholipid liposomes. The ghosts or liposomes are loaded with a concentrated solution of a water-soluble, membrane-impermeable spin label, so that there is a strong exchange broadening of the paramagnetic resonance signal due to labels enclosed within the liposomes or ghosts. Complement-mediated lysis releases the labels into a dilute solution, where a relatively sharp and intense paramagnetic resonance signal is detected. AN UNANTICIPATED RESULT IS ALSO REPORTED: this is the augmentation of release of spin label from loaded ghosts sensitized with egg albumin, in the presence of antibody against egg albumin, complement, and egg albumin in solution, over and above the release in the absence of egg albumin in solution. Comparison with complement fixation suggests that the augmentation of lysis is effected by crosslinking of immune complexes with the cell membrane.