Cell Immunol. a systemic contamination in humans and in other mammals that is controlled by T-cell-dependent immune responses but not completely Metoclopramide HCl eliminated. Control of the acute phase of contamination is usually critically dependent on cytokine-mediated macrophage activation of intracellular killing. Treatment of mice with anti-gamma interferon (anti-IFN-), anti-tumor necrosis factor (anti-TNF), and anti-interleukin-12 (anti-IL-12) neutralizing monoclonal antibodies (MAbs) leads to aggravation of the disease, reinforcing the importance of these cytokines in the in vivo resistance to contamination (2, 3, 11, 18). Furthermore, although neutralization of IL-10 MAbs was not usually effective at changing the course of contamination, the importance of IL-10 in the regulation of parasitism and IFN- production was shown using mice with disrupted IL-10 genes (2, 12). The importance of IL-4 in determining susceptibility to contamination has not yet been fully decided. On the basis of in vitro screening, two contrasting roles for IL-4 have been described: enhancement of intracellular destruction by macrophages (19) and inhibition of IFN–mediated trypanocidal activity (9). Low levels (less than 0.32 ng/ml) of IL-4 in splenocyte culture supernatants from mice infected with have been reported (1, 2). However, IL-4 secretion by spleen cells (SC) was associated with enhanced susceptibility in Tulahen strain-infected BALB/c mice (10). Treatment with a neutralizing anti-IL-4 MAb decreased parasitemia levels and increased survival of BALB/c mice infected with the reticulotropic Tulahen or RA strain of contamination, we studied the responses of 129/J, BALB/c, and C57BL/6 mice with disruption in the IL-4 genes (IL-4?/?) and of the respective wild-type (WT) mice infected with the Y strain of infections and is also a reticulotropic strain (4). In addition, we investigated the effects of treatment of Ten- to 12-week-old female Metoclopramide HCl 129/J, BALB/c, and C57BL/6 IL-4?/? and WT mice were used. 129/J IL-4?/? and WT mice were bred at the DNAX Research Institute. BALB/c IL-4?/? and C57BL/6 IL-4?/? mice were a gift from Luiz Rizzo and were bred, as well as their WT counterparts, at the Department of Immunology, Instituto Cincias Biomdicas, Universide de S?o Paulo. All mice were bred and maintained in specific-pathogen-free conditions and housed in microisolator cages with ad libitum access to food and water. Groups of 5 or 6 mice were infected intraperitoneally (i.p.) with Y strain blood trypomastigotes (BT) obtained as previously described (7). WT and IL-4?/? mice of the highly susceptible 129/J strain were infected with 500 BT, and BALB/c (moderately susceptible) and C57BL/6 (resistant) mice were infected with 5,000 BT. Parasitemia counts were performed by counting the parasites in 5 l of citrated blood obtained from the lateral tail veins. Mortality was evaluated by daily inspection of the cages. Cytokines and anticytokine MAbs and in vivo treatments. 129/J WT mice were treated with the anti-IL-4 MAbs (11B11) or with murine rIL-4 in doses and schedules that have been shown previously to be effective in vivo (6, 15); 11B11 Metoclopramide HCl and rIL-4 were given alone or in association with anti-IL-10 MAb 2A5 or murine rIL-10, respectively. The rat anti-mouse cytokine MAbs, dissolved in sterile 0.15 M NaCl, were administered i.p. on days 0 (before contamination) and 7 after contamination in the following doses per animal: anti-IL-4 11B11 (immunoglobulin G1 [IgG1]), 5 and 2.5 mg; anti–galactosidase GL 113 isotype control (IgG1), 5 and 2.5 mg; anti-IL-10 2A5 (IgG1) or anti-IFN- XMG1.2 (IgG1), 2 and Metoclopramide HCl 1 mg. The recombinant cytokines rIL-4 and rIL-10 were a gift from Satish Menon (DNAX Research Institute). rIL-4 was injected i.p. (5 g complexed to 50 g of MAb 11B11) every third day (8), and rIL-10 was injected i.p. daily (20 g/day/mouse). Spleen cell cultures and in vitro treatments with cytokines or MAbs. SC from WT or IL-4?/? mice of strains 129/J, BALB/c, and C57BL/6 or from 129/J WT FLJ14936 mice treated in vivo with cytokines or anticytokines were obtained on day 11 after contamination as previously described (1) and cultured at 8 106/ml (0.5 ml in 24-well plates) in RPMI 1640 medium containing 10% fetal calf serum, 2 mM l-glutamine, 0.05 mM 2-mercaptoethanol, and penicillin and streptomycin (100 U/ml and 100 g/ml, respectively) (Sigma Chemical Co., St..