Abnormal regulatory control of the antibody response to heterologous erythrocytes in protein-calorie malnourished mice

Influence of protein restriction on lymphoid cell populations characterized by the binding of peanut agglutinin

Cells binding peanut agglutinin (PNA) were studied in the thymus, spleen, and mesenteric lymph nodes from mice placed in the post weaning period on protein-restricted diets containing 8% (R8%) and 4% (R4%) casein. The proportion of PNA+ thymocytes and the absolute number of total and PNA+ cells in the thymus were significantly diminished in R8% and R4% mice. Larger proportion of PNA+ thymocytes showed weaker fluorescence in R8% and R4% than in normally fed (N) animals. Recovery of PNA+ thymocytes was observed in R8% but not in R4% mice at 8 weeks. The number of total and PNA+ cells was significantly diminished although the proportion of PNA+ cells was not modified in the peripheral lymphoid organs of R8% and R4% mice. Results indicate that protein restriction preferentially affected the immature cortical PNA+ cells in the thymus whereas cell depletion in the peripheral lymphoid organs occurred at the expense of both the PNA+ and PNA- subpopulations.

Affinity and distribution of subpopulations of antibody-producing cells in protein-restricted C57BL/6 mice

To study the effect of protein restriction on the affinity of antibodies produced by plaque-forming cells (PFC), C57BL/6 mice were fed diets containing 4% (R4%), 8% (R8%), or 27% (N) casein for 2 (short-term) or 12 (long-term) weeks and immunized with dinitrophenyl (DNP) bovine gamma-globulin in complete Freund's adjuvant. Affinity was assessed by inhibition of plaque formation in the presence of free hapten. Anti-DNP PFC per 10(7) spleen cells were not diminished in short- and long-term R8% mice, and were increased in the former group at certain times after immunization. Affinity of indirect PFC was increased at Days 14 and 21 after immunization in short-term R8% mice and at Day 7 in R4% mice, and was similar in long-term R8% and N animals. No limitation in the heterogeneity of PFC affinities was observed in the restricted groups. Short-term restricted mice showed a rise of the high-affinity PFC subpopulation. The number of mice with hapten-augmentable PFC was diminished in the short-term R8% group at 7 days after immunization and in long-term restricted mice at 14 days, suggesting depressed levels of auto-anti-idiotypic antibodies in protein restriction.

The effect of protein restriction on the development of protective immunity to Leishmania mexicana

Protein deprived C57BL/6 mice infected with 10(3) amastigotes of Leishmania mexicana showed early arrest of lesion progression during the first 5 weeks of infection with subsequent development of progressive non-healing lesions. In contrast, well nourished mice similarly infected developed gradual healing lesions. The early resistance of malnourished mice to 10(3) amastigotes was overcome by a larger dose. After a primary inoculation with 10(3) amastigotes protein deprived mice failed to express protective immunity to a challenge inoculum given at 5 weeks of infection. When challenge was delayed until 10 weeks, protein deprived mice developed lesions at the site of challenge which tended to regress but were unable to manifest the high level of protective immunity seen in normally nourished reinfected controls. A challenge infection given at 5 or 10 weeks prejudiced the control of primary lesions particularly in the group of protein deprived mice challenged at 10 weeks. Equivalent levels of specific delayed hypersensitivity responses were found in protein deprived and normally nourished uninfected mice immunized with killed parasites which imply that the impaired protective immunity observed in protein deprived mice is not due to a deleterious effect of protein deprivation on the ability of the host to develop cellular responses such as delayed type hypersensitivity to Leishmania antigens.

Polyclonal B-cell response to stimulation with Escherichia coli lipopolysaccharide in dietary protein restriction

The polyclonal B-cell response to Escherichia coli lipopolysaccharide was studied in C57BL/6 mice maintained after weaning on either a moderate protein-restricted diet with 8% casein or a normal diet. After in vitro or in vivo stimulation with the endotoxin, autoreactive and anti-hapten antibody-producing cells were quantitated by direct plaque assay, using bromelain-treated mouse erythrocytes and trinitrophenylated sheep erythrocytes as targets. Larger numbers of plaque-forming cells were generated in cultures of spleen cells from dietary-restricted than from normal mice stimulated with various doses of lipopolysaccharide. The number of background plaque-forming cells was also higher in nonstimulated spleen cell cultures from restricted animals. After injection of lipopolysaccharide in vivo, the number of cells producing antibodies to bromelain-treated mouse erythrocytes per 10(7) spleen cells was significantly increased in dietary-deficient mice. The results are discussed in relation to the different sensitivities of lymphocyte populations to protein deficiency and to the possible presence of high levels of endogenous polyclonal B-cell activators in the restricted mice.

Alteration of cell-mediated immunity to Listeria monocytogenes in protein-malnourished mice treated with thymosin fraction V

Cell-mediated immune reactivity, measured by lymphocyte responsiveness to phytohemagglutinin, was higher in both young or aged mice fed a 4% casein diet compared with age-matched controls. Treatment in vivo with bovine thymosin fraction V decreased the responsiveness to phytohemagglutinin of lymphocytes from mice fed either the control or moderately protein-deficient diets when compared with mice treated in vivo with saline. Resistance against Listeria monocytogenes, known to be a cell-mediated immune function, was impaired in young and aged mice which were fed the low-protein diet. Treatment with thymosin was able to significantly improve the cell-mediated immune resistance to L. monocytogenes of moderately protein-malnourished mice. Thymosin treatment impaired the resistance to L. monocytogenes of young or aged mice fed the control diet. The splenic natural killer cell cytotoxicity of protein-malnourished mice was impaired compared with that of mice fed the control diet. Treatment with thymosin did not restore the natural killer cell cytotoxic activity in protein-malnourished mice, but did enhance that activity in control mice.

The effect of diet on immune responsiveness and aging

Immunologic changes which occur during aging include decreased responsiveness to exogenous antigens and increased autoimmune responses. Autoimmune reactions to autologous antigens may interfere with the physiologic function of these antigens and be a factor in the 'wearing out' of tissue during aging. Amelioration of age associated autoimmunity may result in an increased life span. Dietary manipulation has been shown to produce changes in the immune system of experimental animals. Some benefits include a decreased propensity to spontaneous autoimmune disease with a resultant increased life span. Dietary changes may be capable of producing similar beneficial effects in humans.

Resistance to bacterial and parasitic infections in the nutritionally compromised host

Over the past few years the relationships and interactions of diet, disease, and immunology are becoming better defined with the development and understanding of host defenses. Nutritional state, immunity, and disease all influence each other in the hospitalized patient, the elderly, and the young. Disease can alter nutritional needs and immune responses to antigens. The roles of both dietary excesses and deficiencies on cellular, secretory, and humoral immune responses are related to diseases and disease incidence in humans and experimental animals. Malnutrition alters incidence and severity of fungal, bacterial, viral, and parasitic pathogens. The mechanisms of altered disease resistance in nutritionally stressed animal models occurs via changes in the lymphoreticular endothelial system. The effects of common nutritional deficiencies, low protein, and low carbohydrate diets on antibody production, macrophage function, secretory IgA synthesis, and T-cell functions. Nutritional supplementation can increase lymphocyte function and decrease growth of some pathogens and tumors. Alternatively, obesity and high fat have roles in infectious disease and immunity.