Thymosin fraction 5: effects on T cell functions in mice immunosuppressed by severe dietary protein deficiency

The Tolerance Model of Non-Inflammatory Immune Competence in Acute Pediatric Malnutrition: Origins, Evidence, Test of Fitness and Growth Potential

The tolerance model rests on the thesis of a physiologically regulated, albeit unsustainable, systemic attempt to adapt to the catabolic challenge posed by acute prepubescent malnutrition even in its severe forms. The model centers on the immunological component of the attempt, positing reorientation toward a non-inflammatory form of competence in place of the classic paradigm of immunological attrition and exhaustion. The foundation of the model was laid in 1990, and sixteen years later it was articulated formally on the basis of a body of evidence centered on T cell cytokines and interventions with cytokine and hormonal mediators. The benefit originally suggested was a reduced risk of autoimmune pathologies consequent to the catabolic release of self-antigens, hence the designation highlighting immune tolerance. Herein, the emergence of the tolerance model is traced from its roots in the recognition that acute malnutrition elicits an endocrine-based systemic adaptive attempt. Thereafter, the growth of the evidence base supporting the model is outlined, and its potential to shed new light on existing information is tested by application to the findings of a published clinical study of acutely malnourished children. Finally, some knowledge gaps pertinent to the model are identified and its potential for growth consonant with evolving perceptions of immunobiology is illustrated.

Effects of a protein-free diet or food restriction on the immune system of Wistar and Buffalo rats at different ages

The effects of a protein-free diet or food restriction on the immune system were examined in two rat strains, Wistar and Buffalo, in different age-groups. Unlike Wistar rats, Buffalo rats have an unusually hyperplastic thymus and a large number of peripheral T cells. The protein-free diet (PFD) in rats resulted in marked thymic involution together with a reduction of splenic T cells, both in number and in antibody response to sheep red blood cells. The depressive effect of the PFD on the immune system was more serious in young immature rats than in older rats, but less serious in Buffalo rats having enhanced T cell functions regardless of age. Thymic involution was also accelerated in both strains of rats by feeding them a restricted amount of the control diet containing well-balanced nutrients (food restriction, FR). In the FR experiment, no significant change was observed in immune functions of Wistar rats. A slight reduction was observed in the immune functions of Buffalo rats with FR, but absolute levels were distinctly higher in Buffalo rats than in Wistar rats even after FR. These results suggested (1) that the thymic function is sensitive to protein deficiency; (2) that a well-balanced dietary condition is necessary for immunological maturation in the early stage of life and preservation of immune functions at older age; (3) that animals having higher immune functions are more resistant to malnutrition than ordinary ones.

The effects on complement component 3 of dietary variation of protein, fat and vitamin E during growth of young mice

Some studies have shown that nutrition lowers overall immunity to disease. To further elucidate the role of nutrition on immunity, we have investigated the effect on serum Complement C3 by three nutrients, protein, lipid and vitamin E, in BALB/c mice for up to 24 weeks. The group with high dietary vitamin E had slightly higher C3 for the first four months but by the 22nd week was lower than control. The groups receiving high or low protein had, respectively, high or low C3. Injection of thymosin fraction 5 increased the C3, suppressed by the low protein diet. The group on the high lipid diet had high C3 until the 14th week whereupon it declined to control level by the 22nd week. The low lipid diet resulted in low C3 during the early weeks but increased to control level by the 22nd week. We conclude that diet is important to complement mediated immunity of young mice.