Immobilization of Membrane H-2 Antigens by Paraformaldehyde Fixation

The use of specific antibodies coupled to visual markers such as ferritin or fluorescein to study the distribution of cell surface membrane antigens has resulted in the recognition that these membrane components are free to move in the plane of the membrane and that the antibodies used for labeling them may induce changes in their distribution (Frye and Edidin, 1970 ; Taylor et al ., 1971 ; Davis, 1972). Up to the present, labeling studies have been carried out only on fresh, or unfixed, cell membranes . On fixed cells the surface membrane antigens might be immobilized and no longer susceptible to the alterations of their distribution that can be caused by antibodies. We recently demonstrated (Parr and Oei, 1973) that mouse cell membranes fixed with paraformaldehyde were able to bind anti-H-2 antibodies to the same extent as fresh membranes . The purpose of the present work was to determine whether paraformaldehyde fixation immobilizes mouse H-2 antigens on the surface membrane.