[Effect of neonatal immunization with different dosage allergen on the immunity of mice when grown up]

To study the effect of neonatal immunization with different dosage allergen on the immunity of mice when grown.

Fifty neonatal BALB/c mice were divided into 4 groups randomly and subcutaneous injected with different dosage of ovalbumin (OVA) on day 1, 8 and 15 after born [NS group(10): injected with saline alone; NS + AL group (10): injected with saline and AL(OH)3; small dosage (SD) group (15): injected with 10 microg OVA and AL(OH)3; large dosage (LD) group (15): injected with 1000 microg OVA and AL(OH)3]. The mice were then challenged using caudal vein injection on 5 weeks old (NS group and NS + AL group were challenged with saline, SD group and LD group were challenged with 100 microg OVA). The blood was collected 1 week later to examine OVA specific IgE, IgG1 and IgG2a. Mononuclear cells were drawn from the spleen and cultured. Concentration of IL-4, IFN-r, IL-10 was examined in the cultural supernatant. Flow cytometry was used to test the expression of CD4+ IL-4+, CD4+ IFN-gamma+, CD4 IL-10 cells.

It was found that concentration of OVA specific IgE (OVA-sIgE) in SD group (0.33 +/- 0.18) was significantly higher than that of NS (0.07 +/- 0.01) and NS + AL (0.09 +/- 0.04) group (t value was -3.46 and -3.21, all P < 0.01), and LD group (0.17 +/- 0.10) as well (t = 2.58, P < 0.05). The concentration of OVA-sIgE was higher in LD group than that of NS group (t = -2.53, P < 0.05), but similar with that of NS + AL group (t = -2.04, P > 0.05). Both the concentration of OVA-sIgG1 and sIgG2a was higher in SD and LD group than that of NS and NS + AL group (all P < 0.05). The concentration of IL-4, IFN-gamma and IL-10 in the cultural supernatant of spleen mononuclear was all higher in SD group than that of NS and NS + AL group (all P < 0.01). The ratio of IFN-gamma/IL-4 was significantly lower in SD group than that of NS and NS + AL group (t value was 2.14, 3.44, all P < 0.05), while the same ratio was higher in LD group than that of NS and NS + AL group (t value was -2.14, -1.61, all P < 0.05). Ratio of CD4+ IL-4+ cells was significant lower in LD group than that of SD group (P < 0.05), while it was not different with that of NS and NS + AL group (P > 0. 05).

Neonatal immunization with low dosage OVA could generate a specific immunity with Th2 direction, while with large dosage OVA could generate a specific immunity with Th1 direction.