Malnutrition has an adverse impact on cell-mediated, secretory and humoural immunity, as well as on non-specific host defences. Although generalized malnutrition can affect all aspects of host immunity, the impact is greater on T-cell functions and cell-mediated immunity and smaller on B-cell functions as well as humoural immunity. Effects on secretory immunity are intermediate, mainly affecting IgA B-cells. Recent studies have shown that certain chemokines play an important role in regulating homeostatic lymphocyte recirculation through secondary lymphoid organs. The chemokine thymus-expressed chemokine (TECK) is a chemoattractant involved in the ability of lymphocytes to localize in the gastrointestinal tract(Reference Kunkel, Campbell and Haraldsen1).
The aim of the present work was to study the effect on B and T lymphocytes as well as the TECK+ cell population on the intestinal villi of growing rats after the administration of a cereal-based diet as the only source of protein.
Wistar rats were fed a 65 g precooked maize protein/kg diet for 18 d (M). An age-matched control group received a stock diet (C). Body weight (BW; g) was determined, ponderal growth rate (PGR; g/d per 100 g) was calculated and intestines were removed and processed by the Saint Marie technique. Tissue sections were studied by an indirect immunofluorescence technique. CD5+ T-cells and the subsets TCRαβ+, TCRγδ+, CD4+, CD8αα+, CD8αβ+ in the lamina propria (LP) and intraepithelium (iIEL) and IgA-B+ cells in LP were determined (number of cells per thirty fields). Also, the presence of TECK+ cell population was assessed.
There were significant differences between the M and C groups in BW (44.7 (sd 7.83) v. 149.1 (sd 17.7); P<0.0001) and PGR (–0.30 (sd 0.39) v. 5.27 (sd 0.53); P<0.0001). As shown in the Table, the numbers of IgA+ B-cells in the LP and CD5+ T-cells and CD4+, CD8αα+, CD8αβ+, TCRαβ+, and TCRγδ+ T subpopulations in the LP and iIEL of the gut villi for the M group were significantly decreased (P<0.001).
Mean values were significantly different from those for corresponding age-matched C group: *P<0.0001.
Mean values were significantly different from those for corresponding age-matched C group: †0.03>P>0.001.
Differences in the size and cellularity of the gut villi and in the distribution of TECK were also observed in the experimental groups. When histological slides were analysed, the C group showed TECK+ cells in the villi and crypt epithelium, while the M group showed a decreased intensity.
The results show that the intake of a low-quality dietary protein as the only source of protein produces an important disorder in mucosal immunity that could explain the incidence of gastrointestinal infections observed in malnourished children.
