Effects of yogurt ingestion on mucosal and systemic cytokine gene expression in the mouse.

To assess the potential for ingestion of yogurt to modulate immunity, its effects on basal gene expression of cytokines in systemic and mucosal sites were determined in mice. Yogurts were manufactured from pasteurized nonfat dry milk using five commercial starter cultures with or without Bifidobacterium sp. and Lactobacillus acidophilus. Treatment mice were fed the AIN-93G diet mixed 1:1 with unheated yogurt or heat-treated yogurt (wt/wt) for 2 and 4 weeks, and control mice were fed the AIN-93G diet mixed 1:1 (wt/wt) with nonfat dry milk. The viability of the various bacterial groups in unheated yogurts was maintained above 10(6) CFU/g throughout the feeding period. The yogurt-feeding regimens did not significantly affect weight gain. Relative mRNA levels in spleen, mesenteric lymph nodes, or Peyer's patches for the cytokines interferon-gamma, tumor necrosis factor-alpha, interleukin-2, -4, and -6, and the "housekeeping gene" beta2-microglobulin were determined by reverse transcriptase-polymerase chain reaction in conjunction with hybridization analysis. Prolonged feeding of some yogurts decreased expression of several cytokine mRNAs, the depression of tumor necrosis factor-alpha mRNA in the spleen being the most prominent effect. Heat-treated yogurts were more effective in altering cytokine mRNA expression than were unheated yogurts containing viable organisms. Generally, yogurts either had no effect or decreased specific cytokine mRNA in the test organs, regardless of whether they contained Bifidobacterium sp. and L. acidophilus. These results suggest that, in contrast with previous studies in vitro, some yogurt formulations may reduce rather than stimulate basal cytokine expression and that these effects are most prominent in the systemic compartment.

Effects of ingestion of yogurts containing Bifidobacterium and Lactobacillus acidophilus on spleen and Peyer's patch lymphocyte populations in the mouse.

Certain probiotic lactic acid bacteria have been reported to improve immune system function. Here, the effects of ingesting yogurts on lymphocyte populations in the spleens and Peyer's patches were determined in mice. Three probiotic-supplemented yogurts containing Streptococcus thermophilus, Lactobacillus bulgaricus, Bifidobacterium, and Lactobacillus acidophilus and one conventional yogurt containing only S. thermophilus and L. bulgaricus were prepared from commercial starter cultures and used in the study. B6C3F1 female mice were fed the four different types of yogurts mixed with an AIN-93G diet in a 50:50 (wt/wt) ratio. Nonfat dry milk mixed at a 50:50 (wt/wt) ratio with AIN-93G diet was used as the control. After a 14-day feeding period, spleen and Peyer's patches were removed and lymphocytes subjected to phenotype analysis by flow cytometry. Ingestion of the four yogurts had no effect on percentages of CD8+ (cytotoxic T cells), B220+ (B cells), IgA+, or IgM+ cells in spleen or Peyer's patches. The percentage of CD4+ (T helper) cells was significantly increased in the spleens from one group of mice fed a yogurt containing Bifidobacterium and L. acidophilus, and a similar trend was found in the remaining two probiotic-supplemented yogurts. Effects on CD4+ populations were not observed in spleens of mice fed conventional yogurt or in the Peyer's patches of any of the four yogurt groups. In total, the results suggested that ingestion of conventional or probiotic-supplemented yogurts for 2 weeks had very little effect on lymphocyte distribution in the systemic or mucosal immune compartments.

Depression in the quantity of intestinal secretory IgA and in the expression of the polymeric immunoglobulin receptor in caloric deficiency of the weanling mouse.

The objective of this investigation was to determine the influence of weanling caloric restriction on the expression of the polymeric immunoglobulin receptor (pIgR) in the liver and intestine and on the levels of IgA in the blood and intestinal secretions. Male C57BL/6J mice were allocated to a zero-time control group (19 days of age) or to groups fed for 14 days as follows: ad libitum intake of a complete purified diet (19% crude protein, 17 kJ/g gross energy) or restricted intake of a complete diet. Enzyme-linked immunosorbent assays revealed a low concentration of gut luminal immunoglobulin A (IgA) despite a normal concentration of serum IgA in the malnourished mice. The concentration and total quantity per organ of the pIgR were assessed in the liver and intestine by means of Western immunoblotting using an antiserum raised against the secretory component portion of rat pIgR. Malnourished animals exhibited low quantities of hepatic and intestinal pIgR relative to well-nourished controls (8% and 40% of control, respectively) and also exhibited a low concentration (soluble protein basis) of hepatic pIgR (39% of control). The concentration of biliary secretory component was also low in the malnourished animals (20% of well nourished). Despite the low quantity of hepatic pIgR, Western blotting revealed no change in the concentration of monomeric, dimeric, and polymeric forms of serum IgA in the malnourished group relative to well-nourished animals. Caloric deficiency in an experimental system that closely resembles human marasmus results in a decrease in the quantity of the pIgR that is sufficient to account for the low concentration of IgA in the mucous secretions of the intestine. Considered together with recent evidence pertaining to weanling protein deficiency, these results permit the conclusion that the pIgR is a focal point of the impact exerted by metabolically diverse forms of protein-energy malnutrition on mucosal humoral immunocompetence.

Reduction in the quantity of the polymeric immunoglobulin receptor is sufficient to account for the low concentration of intestinal secretory immunoglobulin A in a weanling mouse model of wasting protein-energy malnutrition.

The main objective of this investigation was to determine the influence of protein-energy malnutrition (PEM) in weanling mice on the expression of the hepatic and intestinal polymeric immunoglobulin receptor (pigR), a molecule that transports mucosal immunoglobulin A (IgA) into the intestinal lumen. An experimental system was used that produces systemic wasting (loss of approximately 1.9% of initial body weight per day) and that exhibits fidelity to human PEM in its influence on the concentration of IgA in critical biological fluids as well as in its influence on lymphoid involution and thymus-dependent immunocompetence. Male C57BL/6J mice were allocated to a zero-time control group (19 d of age) or to groups fed for 14 d as follows: free access to a complete purified diet (19% crude protein, 17 kJ/g gross energy) or free access to a low protein diet (0.5% crude protein). The concentration and total quantity per organ of the pIgR were assessed in the liver and intestine by Western immunoblotting using an antiserum raised against the secretory component portion of rat pIgR. Malnourished mice exhibited low quantities of hepatic and intestinal pIgR relative to well-nourished controls (0.4% and 36% of control, respectively) and also exhibited a low concentration (soluble-protein basis) of hepatic pIgR (2% of control). The concentration of biliary secretory component also was low in the malnourished mice (4% of the value for well-nourished controls). Finally, Western blotting revealed an eightfold increase in serum concentration of dimeric IgA in the malnourished group relative to well-nourished mice, whereas the levels of the monomeric form and of the higher order polymers of IgA were elevated by factors of three and two, respectively. In this experimental system, decreased expression of the pIgR is sufficient to account for the low concentration of IgA that is maintained in the mucous secretions of the intestine.

Expansion of the humoral effector cell compartment of both systemic and mucosal immune systems in a weanling murine model which duplicates critical features of human protein-energy malnutrition.

A direct comparison of systemic (spleen) and mucosal (intestine) antibody-producing systems was made in weanling male C57BL/6J mice subjected to wasting protein-energy malnutrition (PEM) by means of a low-protein protocol known to duplicate immunological and physiological features of human malnutrition. ELISA revealed low concentrations of biliary and gut lumen immunoglobulin (Ig) A in malnourished mice concomitantly with a high concentration of blood IgA. The low-protein model, therefore, exhibited fidelity to human protein-energy malnutrition in its influence on the concentrations of the mucosal Ig, IgA, in critical biological fluids. The number of IgA-, IgM- and IgG-containing cells was estimated morphometrically on a per organ basis. The low-protein protocol supported expansion in numbers of mucosal IgA-containing cells (18 x relative to a zero-time control group) and of splenic IgG-containing cells (135x), albeit an attenuated expansion in comparison with that of well-nourished control animals (132x and 571x respectively relative to zero-time controls). Up to terminal differentiation of Ig-containing cells, systemic and mucosal antibody-producing systems exhibited similarly remarkable resistance to wasting malnutrition. Epithelial transport of IgA may be an aspect of the mucosal antibody response which is particularly sensitive to PEM.

Overabundance of CD45RA(+) (quiescent-phenotype) cells within the involuted CD4(+) T-cell population follows initiation of immune depression in energy-deficient weanling mice and reflects involution exclusive to the CD45RA(-) subset.

Previous studies have identified an overabundance of quiescent-phenotype (CD45RA(+)) CD4(+) T cells throughout the lymphoid system of weanling mice at an advanced stage of food intake restriction mimicking marasmus. The objective of this investigation was to determine the timing of this phenomenon relative to the development of depression in cell-mediated immune competence. Two experiments were conducted in which male and female weanling C57BL/6J mice, initially 19 d of age, either were permitted free access to a complete purified diet or were subjected to restricted intake of this diet, producing loss of 1.5-2% of initial body weight daily. In the first experiment, feeding periods of 3, 6, 9, 12 and 14 d were examined, and a zero-time control group (19 d old) was also included. Expression of CD45RA was assessed by flow cytometry in CD4(+) T cells from the blood, spleen and mesenteric lymph nodes. Despite reduction in CD4(+) T-cell numbers, evident in all three lymphoid compartments of the malnourished mice by d 6, energy-restricted mice maintained the numbers of CD4(+)CD45RA(+) T cells at the level found in the zero-time control group. Consequently, the malnourished group exhibited a high percentage of CD4(+) T cells expressing CD45RA by d 9 in the blood and mesenteric nodes and by d 12 in the spleen. In the second study, malnourished and age-matched control groups were sensitized to sheep red blood cells on d 3 and energy-restricted mice exhibited depression in the delayed hypersensitivity response to this antigen when assessed on d 9 after challenge 24 h previously. Energy deficiency pathology includes a shift toward CD4(+) T cell quiescence that may contribute to ongoing immunodepression without being involved in its initiation. Remarkably, this imbalance develops because involution of the CD4(+) subset in the energy-deficient mice is confined to the CD45RA(-) population.