The effect of triiodothyronine on evanescent delayed hypersensitivity to sheep red blood cells and on the primary antibody response to trinitrophenylated Brucella abortus in severely undernourished weanling mice.

Two experiments were conducted using weanling male CBA/J mice. Animals were fed for 14 days a nutritionally complete diet, either ad libitum, or in restricted amounts such that they lost about 30% of their weaning weight during the feeding period. Half the animals from each food intake group received 0.2 mg triiodothyronine (T3)/kg diet. Evanescent delayed hypersensitivity to sheep red blood cells (SRBC) was depressed by malnutrition but not influenced by T3 supplementation. T3 increased nucleated spleen cell number in mice immunized with trinitrophenylated Brucella abortus (TNP-BA). The number of splenic anti-TNP direct plaque-forming cells (PFCs) was decreased by malnutrition when expressed on a per spleen basis. T3 supplements increased splenic PFC number of malnourished mice when results were expressed either per spleen or per 10(6) cells, and increased PFCs per spleen in well-nourished mice. Serum anti-TNP agglutinin titres were unaffected by malnutrition and by T3. The results extend our previous observations as to the improvement by T3 of the primary anti-SRBC antibody response of malnourished weanling mice, and suggest that therapeutic hormonal treatment could be used to improve antibody responses of malnourished individuals. The mechanism of the effect of T3 is unknown, but the lack of effect on delayed hypersensitivity to SRBC implies that T3 (when administered at the dosage of the present protocol) acts on only some immune cells and does not exert a generalized adjuvant effect.