Dietary fatty acid modulation of murine B-cell responsiveness

These studies were designed to determine how dietary fat concentration and degree of saturation influence antibody response to a T-dependent antigen. In vivo fatty acid manipulation did not affect the total number of nucleated spleen cells or IgM or IgG-bearing cells. After primary immunization with sheep red blood cells (SRBC), the number of splenic IgM and IgG antigen specific plaque-forming cells (PFC) was lower in mice fed a diet containing a high level of polyunsaturated fat (PUF, safflower oil) than in mice fed a diet containing minimal essential fatty acids (EFA, 0.5% corn oil). Mice fed a high level of saturated fat (SF, coconut oil) exhibited greater IgM PFC responses than the control. After secondary immunization, the number of IgG-producing cells followed a similar response pattern. These differences were also reflected in the serum anti-SRBC IgM and IgG levels as determined by solid-phase radioimmunoassay. Although the level of linoleic acid in whole lymphocytes has been previously reported to change in direct relation to the serum fatty acid level, no differences in the fatty acid composition of isolated lymphocyte plasmalemma were observed. Thus, changes in the number of antibody-forming cells appear to be inversely related to the levels of linoleic acid in other cell compartments. Fluorescence polarization measurements of the lipopholic probe, 1, 6-diphenyl-1,3,5-hexatriene (DPH), in the purified lymphocyte plasmalemma from mice fed a diet high in PUF indicated an increase in mobility. Polarization values for lymphocyte plasmalemmas from mice receiving diets high in SF were not significantly different from the controls. We conclude that dietary fat modulation of splenic B-cell responses was manifested through changes in the number of cells producing antibody and level of antibody produced, not through total splenic B-cell numbers. This B-cell response can be modified, depending upon the fatty acids available to the cell, and may be related to differential effects upon plasma membrane structure.