Elevated blood interleukin-10 levels and undiminished systemic interleukin-10 production rate prevail throughout acute protein-energy malnutrition in the weanling mouse

The objectives were to determine if blood IL-10 levels rise during the early stages of acute (wasting) pre-pubescent malnutrition in metabolically distinct murine models known to depress inflammatory immune competence and whether systemic IL-10 production is affected in these pathologies. Weanling C57BL/6J mice were assigned to dietary protocols that elicited wasting pathologies mimicking the human diseases of marasmus (restricted-intake group) or incipient kwashiorkor (low-protein group). An age-matched control group also was included. Serum IL-10 bioactivities were assessed in the early (day 3) and advanced (day 14) stages of weight loss, and net systemic IL-10 production was assessed at the same stages of pathology by in vivo cytokine capture. Blood IL-10 levels were elevated in both malnourished groups relative to controls at days 3 and 14 (range of P values: 0.03-0.0001). Further, despite a limited supply of energy and nitrogenous substrates, the systemic IL-10 production rate was at least sustained in the malnourished groups and, in fact, was elevated in the marasmic group (P=0.05) throughout the progression of weight loss. IL-10 emerges as an anti-inflammatory mediator positioned to participate in initiating and upholding the depressed immune competence that accompanies acute pre-pubescent deficits of protein and energy.

Adoptively transferred dendritic cells restore primary cell-mediated inflammatory competence to acutely malnourished weanling mice

Immune depression associated with prepubescent malnutrition underlies a staggering burden of infection-related morbidity. This investigation centered on dendritic cells as potentially decisive in this phenomenon. C57BL/6J mice, initially 19 days old, had free access for 14 days to a complete diet or to a low-protein formulation that induced wasting deficits of protein and energy. Mice were sensitized by i.p. injection of sheep red blood cells on day 9, at which time one-half of the animals in each dietary group received a simultaneous injection of 10(6) syngeneic dendritic cells (JAWS II). All mice were challenged with the immunizing antigen in the right hind footpad on day 13, and the 24-hour delayed hypersensitivity response was assessed as percentage increase in footpad thickness. The low-protein diet reduced the inflammatory immune response, but JAWS cells, which exhibited immature phenotypic and functional characteristics, increased the response of both the malnourished group and the controls. By contrast, i.p. injection of 10(6) syngeneic T cells did not influence the inflammatory immune response of mice subjected to the low-protein protocol. Antigen-presenting cell numbers limited primary inflammatory cell-mediated competence in this model of wasting malnutrition, an outcome that challenges the prevailing multifactorial model of malnutrition-associated immune depression. Thus, a new dendritic cell-centered perspective emerges regarding the cellular mechanism underlying immune depression in acute pediatric protein and energy deficit.

The capacity of noninflammatory (steady-state) dendritic cells to present antigen in the primary response is preserved in acutely protein- or energy-deficient weanling mice

The objective of this investigation was to determine the influence of wasting protein and/or energy deficits on the capacity of dendritic cells to initiate primary responses. Weanling male and female C57BL/6J mice were permitted free access to a complete purified diet, free access to an isocaloric low protein purified diet (combined deficiencies of protein and energy) or restricted intake of the complete diet (energy deficiency) for up to 14 d; a 19-d-old zero-time control group was also included. Malnourished mice lost 1.5-2% of initial body weight daily. Antigen presentation by dendritic cells from spleen and lymph nodes was assessed in vitro by the primary one-way allogeneic mixed lymphocyte reaction using CBA/J mononuclear or CD4(+) T cells as responders. This function was sustained despite advanced weight loss and, remarkably, was increased in cell suspensions from 14-d energy-deficient mice. Antigen presentation by dendritic cells in mononuclear suspensions was examined in vivo using the host-vs.-graft response in CBA/J recipients, and an ontogeny-related increase was sustained in both malnourished groups through 14 d of weight loss. Neither wasting protocol influenced the proportion of mononuclear cells (1-2%) exhibiting dendritic cell phenotype (CD11c(+)F4/80(-/low)) in the cellular suspensions used to study antigen-presenting activity. Consequently, these functional studies are interpretable on a per dendritic cell basis. In the absence of infectious or inflammatory pressure, the dendritic cell retains antigen-presenting capacity despite acute (wasting) deficiencies of protein and/or energy. The results are relevant to presentation of both foreign (adjuvant role) and self (tolerizing role) antigens by the dendritic cell.

The proportion of CD45RA(+)CD62L(+) (quiescent-phenotype) T cells within the CD8(+) subset increases in advanced weight loss in the protein- or energy-deficient weanling mouse

Male and female C57BL/6J mice, initially 19 d old, had free access to a complete purified diet, were fed this diet in restricted daily quantities, or had free access to a low-protein diet. Three separate studies were conducted with feeding periods of 14, 9 or 6 d (n = 7-8 per dietary group and feeding period; 6 d: restricted intake and age-matched controls only). A zero-time control group (19 d old) was included in each study. Malnourished mice lost approximately 2% of initial body weight daily. Naïve-phenotype (quiescent) CD8(+) T cells of the blood, spleen and mesenteric lymph nodes were identified on the basis of surface coexpression of CD45RA and CD62L. Relative to age-matched controls, the percentage of naïve-phenotype CD8(+) T cells was high in energy-restricted groups after 9 d and 14 d of weight loss and in the protein-restricted groups after 14 d (P < or = 0.05). No ontogenetic change was apparent (age-matched vs. zero-time control). Other studies have demonstrated depression in cell-mediated immune competence in both malnutrition models within the first week of weight loss. An overabundance of quiescent-phenotype T cells within the involuted CD8(+) compartment may contribute to established immune depression but not to its initiation in weight loss pathologies.

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.

T cells with a quiescent phenotype (CD45RA+) are overabundant in the blood and involuted lymphoid tissues in wasting protein and energy deficiencies

The objective of this investigation was to determine the influence of distinct forms of acute weight loss on the expression of the quiescence marker, CD45RA, by T cells in several lymphoid compartments including the blood. Male and female weanling mice, CBA/J and C57BL/6J strains, were allocated to the following groups: ad libitum intake of a complete purified diet; restricted intake of the complete diet; and ad libitum intake of an isocaloric low-protein diet. The restricted intake protocol produced weight loss through energy deficiency (marasmic-type malnutrition), whereas the low-protein diet caused wasting through inadequate protein nitrogen and induced a condition mimicking incipient kwashiorkor. In one experiment, weanling mice of both strains were maintained for 14 days according to each of these dietary protocols and, in a supplementary study, C57BL/6J weanlings consumed either the complete diet or the low-protein diet ad libitum for 21 days. Zero-time control groups (19-days old and 23-days old in C57BL/6J and CBA/J strains, respectively) were included in the first experiment to control for ontogeny-related change. Expression of CD45RA was assessed by two-colour flow cytometry in CD4+ and CD8+ T cells from the spleen, mesenteric lymph nodes and blood. Within 14 days, energy-restricted mice exhibited a high percentage of CD4+ T cells expressing CD45RA in all three lymphoid compartments in both mouse strains (an average of 50% CD45RA+ versus 9% in well-nourished controls), and a similar outcome was apparent in the CD8+ subset (93% CD45RA+ versus 63%). Mice fed the low-protein diet required up to 21 days to exhibit the same imbalance within the CD4+ T-cell subset (33% CD45RA+ versus 4% in well-nourished controls). A shift toward a quiescent phenotype occurs throughout the peripheral T-cell system in acute wasting disease. Consequently, the quiescence-activation phenotype of blood T cells reflects the same index in secondary lymphoid organs in such pathologies. Naive-type quiescence among T cells is implicated as a component of depressed adaptive immunocompetence in the advanced stages of diverse forms of acute weight loss.