Effect of low-quality dietary protein on the thymus of growing rats

The status of the thymus of growing rats fed for 45 days after weaning on a low-quality dietary protein (7.5% maize) was compared with that in an age-matched control group receiving a diet containing casein at the same concentration. At the end of the feeding period, body weight (bw) was determined and the thymus was removed; its weight and cell number and the mature T-cell population--characterized by the monoclonal antibody W3/13 using the indirect immunofluorescence technique--were determined. Thymus weight expressed as mg/bw0.75 (3.9 +/- 0.75 vs 7.7 +/- 2.0), cell number (4.4 +/- 2.2 vs 26.3 +/- 7.6), and the absolute number of W3/13+ T cells (1.59 +/- 0.75 vs 17.8 +/- 5.4) were significantly lower (p less than 0.0005) in the experimental group than in the control group. The results suggest severe atrophy of the thymus of weaning animals chronically fed a low-quality protein.