DIETARY-FAT INFLUENCES IA-ANTIGEN EXPRESSION AND IMMUNE CELL-POPULATIONS IN THE MURINE PERITONEUM AND SPLEEN

Peritoneal cells (PEC) and splenocytes were obtained from Listeria monocytogene (LM)-infected or noninfected mice fed a 20% fat diet rich in either (n-3) polyunsaturated fatty acids [(n-3) PUFA diet], linoleate [(n-6) PUFA diet], oleate (MONO diet), or saturated fatty acids (SAT diet) for 6 wk and were assessed for T cells, B cells, macrophages and la expression by flow cytometric analysis. In the peritoneum of noninfected mice, dietary fat did not affect total cell yield or the percentage of B cells, macrophages or la+ cells, but the (n-3) PUFA-fed group had a greater percentage of T cells than did the other groups. Among the LM-infected mice, the (n-3) PUFA-fed group generally had the highest percentage of B cells and the lowest percentages of T cells, macrophages and la+ cells in the peritoneum. Listeria monocytogene infection elevated peritoneal T cell numbers in all mice except the (n-3) PUFA-fed group. The density of la molecules on PEC was 40% lower in mice fed the (n-3) PUFA diet. In the spleen, dietary fat also influenced the immune cell populations and Ia+ cells. Two-color staining of spleen cells revealed that la+ splenocytes were predominately B cells. These data demonstrate that dietary fats influence la expression and immune cell populations and that the effects observed in one immune tissue or cell type may not be readily extrapolated to others.