Humoral immunity in essential fatty acid-deficient rats and mice: effect of route of injection of antigen.

Weanling male Lewis Mai F rats and A/J mice were fed semi-purified diets either adequate or deficient in essential fatty acids (EFA) for 50-60 days. After death livers were excised, the lipids were extracted, and the fatty acid profile was determined. Groups of rats and mice were immunized by injection with sheep red blood cells (sRBC) either i.v. or i.p. One group of rats received an injection of sRBC plus Bordetella pertussis organisms. The plaque-forming cell response (PFC) of all groups was determined. Samples of mouse spleens were analyzed for prostaglandin F2 alpha. EFA-deficient rat and mice liver fatty acid profiles showed elevated levels of omega 7 and omega 9 fatty acids and decreased omega 6 fatty acids. The fatty acid profiles of mice differed quantitatively from the rats. As determined by the ratios of 18:0 to 18:2 omega 6 and 18:2 omega 6 to 20:4 omega 6 mice showed a higher delta 9 and a lower delta 6 desaturase activity. When the antigen was injected i.v. the EFA-deficient animals of both species showed an increased PFC response compared to controls, but when it was injected i.p. there was no difference between dietary groups. The PFC response in rats receiving B. pertussis increased dramatically but the difference between dietary groups was abrogated. As had been previously shown in rats the increase in PFC response in the mice immunized by the i.v. route correlated with a decreased synthesis of PGF2 alpha by the spleen.