Effect of leptin on activation and cytokine synthesis in peripheral blood lymphocytes of malnourished infected children

Abstract

Malnutrition compromises immune function, resulting in reduced resistance to infection. Recent animal and human studies have suggested that leptin is capable of modulating the immune response and that its levels, which are regulated by nutritional status, fall rapidly during starvation. Leptin deficiency is associated with impaired cell-mediated immunity, an increased incidence of infectious disease and an associated increase in mortality. The purpose of this study was to examine the effect of leptin on activation and cytokine production in peripheral blood T cells from malnourished children. The data obtained in the present study demonstrate that leptin produced an increase in the percentage of CD4(+) and CD8(+) cells producing interleukin (IL)-2 and interferon (IFN)-gamma in 24-h cultures. Moreover, leptin decreased the percentage of CD4(+) and CD8(+) cells producing IL-4 and IL-10, and enhanced activation of circulating T cells when co-stimulated by phorbol 12-myristate 13 acetate (PMA)-ionomycin. Leptin enhanced the expression of activation markers CD69 and CD25 in both CD4(+) and CD8(+) cells after 5 h of stimulation. In conclusion, the results obtained show that leptin modulates CD4(+) and CD8(+) cell activation towards a T helper 1 (Th1) phenotype by stimulating the synthesis of IL-2 and IFN-gamma. In contrast, leptin decreases IL-4 and IL-10 production. Moreover, leptin enhanced the expression of CD69 and CD25 on CD4(+) and CD8(+) cells after stimulation with PMA-ionomycin.

Fig. 1

(a) The lymphocyte gate set in the forward scatter–side scatter distribution. (b) The peridinin chlorophyll-SSC distribution; this gate was set on to restrict the analysis to CD4⁺ or CD8⁺ cells. For the analysis of cytokine production and activation markers the cells were passed by windows (a) and (b).

Fig. 2

Effect of malnutrition on the percentages of cytokine-positive cells from well-nourished infected (WNI, n = 12) and malnourished (MN, n = 12) children. The percentage of interleukin (IL)-2-, interferon (IFN)-γ-, IL-4- and IL-10-producing resting cells in CD4⁺ and CD8⁺ cells is shown in the upper panel. The percentage of IL-2-, IFN-γ-, IL-4- and IL-10-producing activated cells in CD4⁺ and CD8⁺ cells is shown in the lower panel. Data are based upon flow cytometric analysis of 10 000 events and are means ± standard error. *P < 0·01; + +P < 0·05; +P < 0·005 and **P < 0·001; in all cases the difference was between WNI versus MNI group.

Fig. 3

Expression of activation antigen (a), CD25; (b), CD69 by CD4⁺ and CD8⁺ cells from unstimulated and stimulated peripheral blood cells. Cells were activated with phorbol 12-myristate 13 acetate (PMA)–ionomycin for 5 h at 37°C. Cells were stained and analysed as described in the Methods section. Data are based upon flow cytometric analysis of 10 000 events and are means ± standard error. Results are expressed as percentage of positive cells. (a) *P < 0·01 versus CD4⁺ stimulated cells from WNI children; **P < 0·001 versus CD4⁺ unstimulated cells from WNI children; +P < 0·05 versus CD8⁺ unstimulated cells from WNI children and ++P < 0·01 versus CD8⁺ stimulated cells from WNI children. (b) *P < 0·01 versus CD4⁺ stimulated and unstimulated cells from WNI children; **P < 0·001 versus CD8⁺ unstimulated cells from WNI children; ++P < 0·001 versus CD8⁺ stimulated cells from WNI children. All bars were significant different in stimulated versus unstimulated cells (P < 0·05).

Fig. 4

Effect of leptin on the cytokines production in peripheral blood lymphocytes of malnourished infected children. The percentage of interleukin (IL)-2-, interferon (IFN)-γ-, IL-4- and IL-10-producing cells in CD4⁺ cells is shown in the upper panel (a, b). The percentage of IL-2-, IFN-γ-, IL-4- and IL-10-producing cells in CD8⁺ cells is shown in the low panel (c, d). Cells were activated with phorbol 12-myristate 13 acetate (PMA)–inomycin for 5 h at 37°C. Data are based upon flow cytometric analysis of 10 000 events and are means ± standard error. *P < 0·05, **P < 0·001, +P < 0·01, + +P < 0·005 versus cells without leptin treatment.

Fig. 5

Leptin effects on activation antigens expression CD69 and CD25 by CD4⁺ (a) and CD8⁺ (b) cells from resting and activated peripheral blood cells from malnourished-infected children. Cells were activated with phorbol 12-myristate 13 acetate (PMA)–ionomycin for 5 h at 37°C. Cells were stained and analysed as described in the Methods section. Data are based upon flow cytometric analysis of 10 000 events and are means ± standard error. *P < 0·05 and +P < 0·01 versus cells without leptin treatment.