Influence of dietary fat concentration and saturation on immune ontogeny in mice.

Dietary fat modulation of immune responsiveness was studied using a murine model subjected to prenatal and postnatal dietary manipulation. The weight of lymphoid associated organs, particularly the spleen, thymus and liver were significantly influenced by dietary fat saturation and concentration whereas other organs studied were not influenced by this manipulation. The serum immunoglobulins IgG1 and IgG2, but not IgM or IgA, increased in mice fed the polyunsaturated fat (PUF) diet as compared to the levels in those mice fed the saturated fat (SF) diet. While dietary manipulation generally did not influence the peripheral differential blood cell counts, the percentage of immunoglobulin positive splenic cells changed with dietary manipulation; the percentage of T cells, however, was not influenced by the experimental diets. In contrast, T-cell blastogenesis was influenced by both saturation and concentration of dietary fat whereas B-cell transformation was influenced by neither variable. Changes in T-cell responses were manifested through changes in the lymphocytes, and not cell numbers; PUF, particularly high levels, suppresses lymphocyte blastogenesis whereas low levels or a deficiency of PUF intensify this response. It is concluded that dietary fats influence the modulation and level of immune function.