SOME ASPECTS OF THE CAUSES OF ENHANCED IMMUNE-RESPONSE OF IN-VITRO FROZEN ASCITES FIBROSARCOMA TUMOR-CELLS IN MICE

Estimation of 3 M KCl-extracted ascites fibrosarcoma (AFS) tumor cell membrane peripheral proteins in native and frozen tumor cells showed a pproximately a three-, four-, and fivefold increase per 1 x 10(6) cell s of single-, three-, and programmed three-cycle frozen AFS tumor cell s, respectively, compared to the same number of native cells, indicati ng an increase in surface membrane protein concentration with freezing . The 10% gel (homogeneous) electrophoretic (SDS-PAGE) study of 3 M KC l-extracted native and frozen cell membrane proteins showed (i) membra ne proteins of native cells resolve into many more components compared to those of any frozen membranes, i.e., single, three, and programmed three cycle, the components decreasing in that order; (ii) the concen tration of larger-molecular-weight protein fractions (greater than or equal to 75 kDa) decreases while those of smaller fractions (14 to 24 kDa) increase in frozen cells, with the maximum being in the programme d three-cycle frozen group. In contrast, the native cell membrane is r ich in higher-molecular-weight proteins (greater than or equal to 75 k Da) with concentrations slowly decreasing toward lower-molecular weigh t fractions. Thus, the probable reasons for increased immune response of animals immunized with frozen AFS tumor cells are (i) absolute incr ease in cell surface protein concentrations as given by 3 M KCl extrac tion of cell membrane peripheral protein estimation in AFS tumor cells postfreeze; (ii) cell-surface protein pattern which is heterogeneous before freezing becomes relatively more homogeneous following freezing of AFS tumor cells; and (iii) depolymerization and breaking of higher -molecular-weight components which increase the concentration of termi nal-sequence antigenic determinants and increase accessibility of dete rminant groupings by removing steric hindrance following freezing. (C) 1995 Academic Press, Inc.