Photodynamic effects of protoporphyrin on the architecture of erythrocyte membranes in protoporphyria and in normal red blood cells.

Protoporphyrin causes a photodynamic damage of the red blood cell membrane. After illumination of red blood cells in the presence of protoporphyrin three effects can be observed: 1. Red blood cell membranes show particle aggregation on the outer and inner fracture face, as seen in freeze-etch electron microscopy. 2. Electrophorograms of membrane proteins show an increasing protein association, not disrupted by sodium dodecyl sulfate. 3. The immunological response of A+ red cells to anti A serum is progressively retarded. It seems likely that these effects are interrelated consquences of the protoporphyrin-induced photodynamic membrane damage.