Modulation of cytokine production and response phenotypes in murine trichuriasis

BALB/K mice are usually resistant to infection with the intestinal nematode parasite Trichuris muris and exhibit a Th2 dominated (IL-5, IL-9) response. Conversely in B10.BR mice, which are unable to expel T. muris, Th1 type (IFN-gamma producing) cells predominate. We have manipulated the course of infection in these two strains of mice such that the period of host-parasite contact is extended in the former and curtailed in the latter. Extension of host-parasite contact in BALB/K mice beyond normal (day 21) resulted in the modulation of cytokines produced by in vitro concanavalin A (Con-A) stimulated MLNC away from IL-5 and IL-9 (Th2-type cytokines) in favour of the Th1-type cytokine IFN-gamma. Curtailment of host parasite contact in B10.BR mice to less than 21 days resulted in elevated production of IL-5 and IL-9 by MLNC in the absence of elevated IFN-gamma levels. Thus modulation of expulsion phenotype also modulates cytokine production by T-cells in the MLN draining the site of infection, with a Th2 response being associated with resistance and a Th1 type response with the inability to expel the parasite. Mechanisms by which the modulated cytokine profiles arise are discussed.     

Lymphocyte, antibody and cytokine responses during concurrent infections between helminths that selectively promote T-helper-1 or T-helper-2 activity

The injuence of Trichinella spiralis on infections with Trichuris murk was studied in non-responder B10. BR mice. Mice infectedonly with T. muris were unable to expel parasites and had many adult worms 35 days later. Infection with 300 larvae of T. spiralis, given seven or 14 (but not 28) days after T. muris, enabled mice to expel up to 90% of T. muris; expulsion of T. spiralis was not altered. Concurrently infected mice produced less T. murisspecijic IgG2a antibody than mice infected with T. muris only, andshowed higher proliferative responses when spleen and mesenteric lymph node cells were cultured in vitro with T. murk antigens. When T. spiralis was present mucosal mast cells were generated in T. muris-infected mice, whereas almost no mast cells were seen with only T. muris. Lymphocytes from doubly-infected mice produced significantly more interleukin 4 and 5 (IL-4, IL-5) and significantly less interferon-gamma (IFN-y) when stimulated in vitro with Concanavalin A (Con-A) than cells from mice infected with T. murk only. These data demonstrate that BI0.BR mice, which in single infections produce a Thl response to T. muris and develop no protective immunity, can mount a protective T-helper-2 (Th2) response and expel T. murk when concurrently infected with the ‘Th2 inducing’ nematode T. spiralis.     

NK1.1+ cell depletion in vivo fails to prevent protection against infection with the murine nematode parasite Trichuris muris

Protection against the murine nematode parasite Trichuris muris has been shown to involve interleukin 4 (IL-4). NK1.1+ T cell receptor alphabeta+ cells, designated Natural Killer T (NKT) cells, produce a large amount of IL-4 in response to anti-CD3 stimulation and numerous pieces of evidence suggest that NKT cells provide the initial source of IL-4 for T helper 2 (Th2) priming. These observations allow the hypothesis that NKT cells produce a large amount of IL-4 in response to T. muris infection and augment Th2 responses and IL-4 production, thus achieving protection against T. muris. To investigate the involvement of NKT cells in protection against T. muris infection, NK1.1+ cell-depleted B10.BR mice were prepared by anti-NK1.1 monoclonal antibody injection. Efficient expulsion of T. muris worms occurred in NK1.1+ cell-depleted infected mice, and the expulsion kinetics of T. muris worms, the levels of IL-4 production by mesenteric lymph node cells, and the kinetics of the specific IgG1 and IgG2a responses to T. muris were similar to those in mouse IgG-treated or non-treated control B10.BR mice. These observations suggest that NK1.1+ cells and NKT cells are not involved in the induction of Th2 responses and protective immunity to T. muris infection.     

Protection in lambs vaccinated with Haemonchus contortus antigens is age related, and correlates with IgE rather than IgG1 antibody

The involvement of mucosal mast cells (MMC) in protection against infection with the murine nematode parasite Trichuris muris was studied in genetically mast cell-deficient WBB6F1-W/Wv mice and their normal littermates WBB6F1-+/+ mice. Expulsion of T. muris worms occurred in infected +/+ mice, whereas no worm expulsion was observed in infected W/Wv mice where the infection persisted until at least day 46 postinfection. No MMC responses were induced in either infected W/Wv or +/+ mice. Specific IgG1and IgG2a antibodies to T. muris excretory/secretory antigens were observed in infected W/Wv and +/+ mice, and antibody production showed similar kinetics. Interleukin 4 production by concanavalin A (Con A)-stimulated mesenteric lymph node cells (MLNC) was induced preferentially in infected +/+ mice. T. muris infection increased the levels of IFN-gamma produced by Con A-stimulated MLNC of infected W/Wv and +/+ mice, with the levels of IFN-gamma in infected W/Wv mice being higher than those in infected +/+ mice. Taken together, these results indicate that W/Wv and +/+ mice are susceptible and resistant to T. muris infection, respectively, and that MMC responses are not required for protective immunity.     

T-cell activity associated with secondary infections and implanted cysts of Echinococcus granulosus in BALB/c mice

Selected cytokine profiles of lymphocytes were assessed in BALB/c mice infected with protoscoleces of Echinococcus granulosus . Late stages of the infection (three months +) were characterized by more dominant Th2 activity with elevated IL-4 and IL-10 and reduced IFN-γ output by Con-A and antigen stimulated splenocytes. Circumparasitic leucocytes produced mainly IL-10 by five months post infection. A peak in IFN-γ production in the first month of infection may suggest Th1 or Th0 activity at this time and this may be correlated with initial protoscolex death. In addition, cytokine profiles from mice implanted with intact hydatid cysts were also assessed. At two weeks post implantation all cysts were still viable and cytokine production was characterized mainly by elevated IL-10 production. However, at four months post implantation, some of the cysts from two mice had been killed whilst all cysts in the remaining mouse remained viable. In the mice where dead cysts were present, elevated levels of IFN-γ were detected from splenocytes and circumparasitic cells. Elevated IL-4 was also evident with the splenocytes. In the mouse with viable cysts IFN-γ production was reduced. Results indicate that IFN-γ (Th1) activity may be correlated with killing of both protoscoleces and established cysts of E. granulosus.     

Genetic variation in the humoral immune responses of mice to the nematode Trichuris muris

Genetically based differences in the antibody responses to the large intestinal nematode Trichuris muris were studied in two groups of H-2 congenic strains of mice that differed in their relative resistance to infection with this parasite. The primary antibody response to parasite excretory/secretory (E/S) antigen was predominantly an IgG response with the strains forming two distinct groups, defined by their genetic background. The more susceptible B10 genetic background mice had strikingly higher antibody levels than mice of the BALB genetic background. Superimposed upon these background effects were clearly defined influences attributable to H-2-linked genes, strains which differed genetically only at H-2 loci exhibiting differences in the kinetics of the antibody response. Only B10.G and B10.BR mice showed any great increase in IgM levels post-infection. No IgA specific to E/S antigen was detected in the peripheral circulation of any strain at any time post-infection. Antibody responses to a 40-43 kD antigen revealed clear H-2-linked gene effects, with mice sharing the H-2k haplotype (B10.BR, BALB/K) exhibiting considerably higher total antibody levels than strains expressing other haplotypes; mice of the H-2d haplotype (BALB/c, B10.D2/n) responded very weakly to this antigen. A Western blot analysis of antigen recognition by antibody revealed similarities between the mouse strains in their total antibody responses to T. muris E/S antigen. However, immunoprecipitation studies showed that in general the more susceptible B10 congenic strains had wider spectra of antigen recognition than the BALB congenics. Strains sharing the same H-2 haplotype had dissimilar antigen recognition profiles, but strains sharing the H-2b haplotype (B10, BALB/B) recognized a low mol. wt antigen (20-23 kD) not recognized by any other strain, suggesting an exclusively H-2b restriction in the recognition of this antigen. These results support the conclusion that both H-2-linked and background genes play important roles in controlling the humoral immune response to T. muris infection.     

MHC-restricted antibody responses to Trichuris muris excretory/secretory (E/S) antigen

Two panels of H-2 recombinant mice were used in a detailed serological study to analyse the role of H-2-linked genes in the control of the antibody response to excretory/secretory (E/S) antigens of Trichuris muris. An apparent H-2q (I-Aq) restriction on the early development of high levels of IgG1 antibody to E/S antigen was revealed by ELISA. No such restriction was demonstrated for the specific IgG2a response patterns. Recognition of two high molecular weight antigens (90-95 kDa, 105-110 kDa) by IgG antibodies was also shown to be almost exclusively H-2q restricted and may be related at least in part to the high antibody levels seen for H-2q strains of mice. Immune serum from resistant (B10.BRxB10.G) F1 hybrid mice (H-2q/k) containing high levels of IgG1 antibodies specific for T. muris E/S and IgG antibodies which recognized the 90-95 kDa and 105-110 kDa E/S antigens was effective in transferring protection to the non-responsive B10.BR mouse strain as seen on day 35 post-infection (p.i.). It is suggested that the IgG responses described for the generally very resistant H-2q mouse strains may contribute to, but not be an absolute requirement for, protective immunity, antibody-mediated damage facilitating a subsequent cellular attack in certain strains of mice.     

MHC-restricted antibody responses to Trichuris muris excretory/secretory (E/S) antigen

Summary Two panels of H-2 recombinant mice were used in a detailed serological study to analyse the role of H-2-linked genes in the control of the antibody response to excretory/secretory (E/S) antigens of Trichuris muris. An apparent H-2 ^q ( 1-A ^q) restriction on the early development of high levels of IgGl antibody to E/S antigen was revealed by ELISA. No such restriction was demonstrated for the specific IgG2a response patterns. Recognition of two high molecular weight antigens (90–95 kDa, 105–110 kDa) by IgG antibodies was also shown to be almost exclusively H-2 ^q restricted and may be related at least in part to the high antibody levels seen for H-2 ^q strains of mice. Immune serum from resistant (B10.BR × B10.G) Fl hybrid mice ( H-2 ^qk) containing high levels of IgGl antibodies specific for T. muris E/S and IgG antibodies which recognized the 90–95 kDa and 105–110 kDa E/S antigens was effective in transferring protection to the non-responsive B10.BR mouse strain as seen on day 35 post-infection (p.i.). It is suggested that the IgG responses described for the generally very resistant H-2 ^q mouse strains may contribute to, but not be an absolute requirement for. protective immunity, antibody-mediated damage facilitating a subsequent cellular attack in certain strains of mice.     

Accumulation of eosinophils in intestine-draining mesenteric lymph nodes occurs after Trichuris muris infection

Eosinophils have recently been demonstrated capable of localizing to lymph nodes that drain mucosal surfaces, in particular during T helper 2 (Th2) responses. Resistance of mice to infection with the gastrointestinal nematode Trichuris muris depends critically on mounting of a Th2 response and represents a useful model system to investigate Th2 responses. Following infection of resistant BALB/c mice with T. muris, we observed accumulation of eosinophils in intestine-draining mesenteric lymph nodes (MLNs). The accumulation of MLN eosinophils was initiated during the second week of infection and peaked during worm expulsion. In contrast, we detected a comparably late and modest increase in eosinophil numbers in the MLNs of infected susceptible AKR mice. MLN eosinophils localized preferentially to the medullary region of the lymph node, displayed an activated phenotype and contributed to the interleukin-4 (IL-4) response in the MLN. Despite this, mice genetically deficient in eosinophils efficiently generated IL-4-expressing CD4(+) T cells, produced Th2 cytokines and mediated worm expulsion during primary T. muris infection. Thus, IL-4-expressing eosinophils accumulate in MLNs of T. muris-infected BALB/c mice but are dispensable for worm expulsion and generation of Th2 responses, suggesting a distinct or subtle role of MLN eosinophils in the immune response to T. muris infection.     

The role of IL-4, IL-13 and IL-4Ralpha in the development of protective and pathological responses to Trichinella spiralis

T helper type 2 (Th2) responses have been shown to be important in protective responses to gastrointestinal (GI) helminth infections and in the development of the intestinal pathology accompanying expulsion of the parasite. Different inbred mouse strains have been shown to develop different cytokine profiles following infection with GI helminths with increased resistance observed in those strains where Th2 cytokines predominate. The aim of this study was to determine the role of IL-4, IL-13 and IL-4Ralpha and the impact of host background on the development of the protective and pathological responses induced by infection with the gastrointestinal helminth Trichinella spiralis. IL-4, IL-13 and IL-4Ralpha were required for the generation of Th2 responses to T. spiralis; however, the role these responses play in the development of protection and enteropathy was less clear. IL-4Ralpha-deficiency mice resulted in substantially reduced parasite expulsion, intestinal pathology and Th2 responses. Similarly, lack of IL-13 resulted in inhibited expulsion and the development of enteropathy. Although Th2 responses were reduced in BALB/c IL-4-/- mice, neither expulsion nor enteropathy were different from wild-type mice. In contrast, C57BL/6 IL-4-/- exhibited delayed expulsion and reduced pathology, suggesting that host genetics are important in the function of individual cytokines. Thus, differences in background genotype may be an important component in the development host protection and the development of intestinal pathology accompanying the loss of GI helminths.     

Resolution of Cryptosporidia! infection in mice correlates with parasite-specific lymphocyte proliferation associated with both Th1 and Th2 cytokine secretion

This study was designed to investigate and characterize T-cell responses which lead to elimination of a primary infection of Cryptosporidium muris in BALBjc mice. The proliferative response of spleen cells to parasite antigen was measured by uptake of ³H-thymidine and, in parallel, supernatants were removed from cells to measure levels oflFN-γ, TNF, IL-2 and IL-4 by ELISA. Oocyst excretion in faeces was first detected on day 10 post infection (p.i.); the level of shedding subsequently increased until day 14 and then declined until no oocysts were detected by day 25. The proliferative response of spleen cells from infected animals was similar to control levels up to day 14p.i. but increased significantly on day 21 and was even greater on day 26. IFN-γ and IL-2 were detected initially on day 14 p.i. and significantly higher concentrations were found on days 21 and 26. IL-4 secretion was also detected, but not until day 21 p.i., and production of TNF was not found at any time. Depletion of T-cells or CD4 + cells from spleen cells cultured with antigen resulted in a significant decrease in the levels of cytokine detected. These results indicated, therefore, that in BALB/c mice there was a correlation between the development of immunity to C muris infection and both a parasite antigen-specific proliferative response and T_hl and T_h,2 cytokine production by spleen cells     

Zinc deficiency and energy restriction modify immune responses in mice during both primary and challenge infection with Heligmosomoides polygyrus (Nematoda)

This study characterized the consequences of zinc-sufficient (Zn+, 60 mg zinc/kg diet, ad libitum ), zinc-deficient (Zn−, 0.75 mg zinc/kg diet, ad libitum ) and energy-restricted (ER, 60 mg zinc/kg diet which was restricted to match food intake of Zn− mice) diets on the in vivo and in vitro immune response of BALB/c mice during both primary and challenge infection with Heligmosomoides polygyrus . In Zn+ mice, both primary and challenge infection with H. polygyrus induced not only a strong Th2 response (IgE, IgG1, eosinophilia, IL-4, IL-5, IL-10), but also elements of a Th1 response (IgG3, IFN-γ). Zinc deficiency significantly depressed Th2-dependent antibody production during both primary and challenge infection, and reduced mitogen and antigen-induced T cell proliferation during the challenge infection. Th2 cytokine production was reduced by zinc deficiency (IL-4), energy restriction (IL-5) and by zinc deficiency possibly in combination with energy restriction (IL-10) during the primary infection whereas Th1 cytokine production (IFN-γ) was depressed during the challenge infection by zinc deficiency, possibly together with energy restriction. Both zinc deficiency and energy restriction reduced eosinophilia with the more profound effect being exerted by zinc deficiency. Thus, both zinc deficiency and its concurrent energy restriction modify immune responses in the mice during primary and challenge infection with H. polygyrus.     

In vivo treatment with recombinant IL-12 protects C57BL/6J mice against secondary alveolar echinococcosis

Using an experimental model of hepatic Echinococcus multilocularis infection in C57BL/6J mice, intraperitoneal administration of 0.8 μg of recombinant IL-12 to mice with an established infection was shown to reduce the parasite burden as soon as two weeks after the end of treatment. At that time, in vitro Echinococcus multilocularis -induced spleen T cell proliferative responses as well as IFN-γ and IL-5 production were higher in IL-12 treated mice than in untreated mice. Administration of 0.8 μg of IL-12 at the time of infection was shown to be without effect on the parasite establishment. However, this treatment greatly inhibited the subsequent metacestode development. Indeed, ten weeks after infection, it induced a complete healing in 37.5% of mice. At that time, the development of metastases was inhibited in 68.75% of IL-12-treated mice. This reduction of parasite burden was mainly associated with a strong proliferation of spleen cells to E. multilocularis antigen and with a high IFN-γ production. Altogether, our results show that IL-12 is of crucial importance in inhibiting the larval growth after the metacestode establishment in the liver and suggest that this cytokine could be of potential value in the treatment of human alveolar echinococcosis .     

Exogenous cytokines released by spleen and Peyer's patch cells removed from mice infected with Giardia muris

The role that T and B lymphocytes play in the clearance of Giardia muris in the mouse model is well known, but the cytokines produced by CD4⁺ T cells in response to Giardia antigenic stimulation are unknown. In this study, we have determined how Giardia trophozoite antigenic crude extract and T cell mitogens can trigger the production of cytokines by Peyer's patch and spleen cells removed from infected animals. When Giardia trophozoite proteins were used to challenge the cells in vitro , IL-4, IL-5 and IFN-γ were not detected in the culture supernatant. When the cells were challenged with Con-A, all three cytokines were released in vitro . However, the level of each cytokine released by the spleen or Peyer's patch cells varied with the latent, acute and elimination phases of the infection. The high levels of IL-4 and IL-5 released by Peyer's patch cells confirm the importance of IgA in the control of the infection. However, we propose that the relative success of G. muris in completing its life cycle in a primary infection might be due, in part, to the stimulation of a Th2-type response (IL-4, IL-5). A stronger Th1 response (IFN-γ) may lead to a better control of the primary infection .     

Recovery from Strongyloides venezuelensis infection in Lewis rats is associated with a strong Th2 response

In this study, we investigated the characteristics of the infection and subsequent immunity induced by Strongyloides venezuelensis in Lewis rats. Animals were infected with 4000 L3 of S. venezuelensis and number of eggs per gram of faeces indicated an acute phase around day 8 and a recovery phase around day 32 after infection. A strong Th2 polarization during recovery phase was ascertained by a significant increase in IgG1 and IgE compared with that in the acute period. A shift in the cytokine profile confirmed these findings. A predominant production of IFN-γ during the acute phase was followed by IL-10 production during recovery. Together these findings show that experimental infection of Lewis rats with S. venezuelensis presents a kinetics of parasite establishment and immunity similar to that described in other models of helminthic infection.     

Mesenteric lymph node T cells but not splenic T cells maintain their proliferative response to Concanavalin-A following peroral infection with Toxoplasma gondii

The suppression of T cell responsiveness which occurs after infection with Toxoplasma gondii in mice has been widely studied using spleen cells. Because the natural route of infection with T. gondii is the peroral route, we examined the proliferative responses of mesenteric lymph node (MLN) cells, in addition to spleen cells, to Concanavalin-A (Con-A) in mice perorally infected with T. gondii. Proliferative responses of spleen cells were significantly suppressed seven and ten days after infection when compared with spleen cells from uninfected mice (62% and 91% reduction, respectively). In contrast, proliferative responses of MLN cells from these infected mice did not differ from those of normal MLN cells. Since IFN-γ-induced reactive nitrogen intermediate (RNI) production has been reported to play a major role in suppression of proliferative responses in spleen cells of infected mice, we compared production of IFN-γ and RNI by spleen and MLN cells following infection. MLN cells produced as much IFN-γ as did spleen cells, but produced 70% less nitrite (as a measure of RNI) after Con-A stimulation. Proliferative responses of MLN cells were suppressed when co-cultured with spleen cells from infected mice, and addition of an inhibitor of RNI to these co-culture inhibited this suppression, suggesting that reduced RNI production by MLN cells contributes to their maintenance of higher proliferative responses. These results demonstrated a clear difference in activity of T cells in the MLN and spleen during the acute stage of the infection .     

IL-17-producing CD4+ T cells, pro-inflammatory cytokines and apoptosis are increased in low risk myelodysplastic syndrome

Immunological responses are increasingly recognised as being important in the initiation and progression of myelodysplastic syndrome (MDS). Indeed, autoimmune diseases commonly occur in association with MDS, particularly in subtypes with a low risk of leukaemic transformation. This study showed for the first time that the numbers of CD3⁺ CD4⁺ IL-17 producing T cells (Th17) were markedly increased in low risk MDS compared with high risk MDS ( P  < 0·01). An inverse relationship between the numbers of Th17 cells and naturally occurring CD4⁺CD25^high FoxP3⁺ regulatory T cells (Tregs) were also described. The Th17:Tregs ratio was significantly higher in low risk disease ( P  < 0·005) compared with high risk MDS and was correlated with increased bone marrow (BM) apoptosis ( P  < 0·01). Tregs from MDS patients suppressed interferon-γ (IFN-γ) secretion by effector CD4⁺ T cells but had no effect on interleukin (IL)-17 production. In addition, the serum levels of IL-7, IL-12, RANTES and IFN-γ are significantly elevated in low risk MDS, while inhibitory factors, such as IL-10 and soluble IL-2 receptor, are significantly higher in high risk disease. The 'unfavourable' Th17:Tregs ratio in low risk MDS may explain the higher risk of autoimmunity and the improved response to immune suppression in patients with low risk MDS compared to those with high risk disease.     

A comparison of local and peripheral parasite-specific antibody production in different strains of mice infected with Trichuris muris

The serum parasite-specific antibody responses of different mouse strains infected with Trichuris muris reflect the nature of the T-helper response mounted by the host, in that resistant Th2-responding strains, such as BALB/K, produce immunoglobulin (Ig)G1 and susceptible predominantly Th1-responding strains, such as AKR, produce IgG2a and IgG1. However, the kinetics of antibody production in the sera, as determined by enzyme-linked immunosorbent assay, do not reflect infection status in that resistant strains can expel their worm burdens before antibodies are detectable in the sera. Here, we show that parasite-specific antibody production by in vitro lipopolysaccharide-stimulated mesenteric lymph node cells (MLN) not only correlate with serum antibody isotypes, but also follow expulsion kinetics. Additionally, the antibody levels seen locally match changes in absolute B220+ cell numbers in the MLN (determined by flow cytometry) and changes in MLN parasite-specific plasma cells in the MLN (determined by ELISPOT). These results show that B cell responses are tightly regulated locally in both resistant and susceptible strains of mice infected with T. muris.     

T-cell cytokine profiles are altered in childhood asthma exacerbation

Background and objective:   Stable asthma is characterized by the production of Th2 cytokines, although Th1 cytokines may play a key role in aspects such as airway hyper-responsiveness. This study explored cytokine profiles associated with asthma exacerbation.
Methods:   Intracellular T-cell cytokine production was measured in 16 children with acute severe asthma (emergency department), after convalescence (6 weeks, n  = 13), with stable disease (after 6 months, n  = 7) and in 14 age-matched hospital controls. Flow cytometry was used to identify CD4+ and CD8+ cells and to quantify intracellular T-cell production of the cytokines interferon (IFN)-γ, IL-4 and IL-13. Cytokine production was compared using analysis of variance and random-effects generalized linear models and associations were examined using Pearson's correlation.
Results:   Cytokine production was evident in CD4+ and CD8+ cells, and compared with asthmatic children, non-asthmatics had a higher percentage of IFN-γ+CD4+ cells ( P  = 0.01). The percentage of CD8+IFN-γ+ cells was increased in the convalescent phase compared with acute ( P  = 0.009) and stable asthma ( P  = 0.004). IL-4+ cells were not significantly altered. IL-13 levels were higher in acute disease than in stable asthma ( P  = 0.009 in CD4+ cells) and IFN-γ/IL-13 ratios indicated a Th2 profile during exacerbation ( P  = 0.005 in CD4+ cells).
Conclusions:   IL-13, rather than IL-4, may play a pro-inflammatory role during acute severe asthma, whereas IFN-γ responses were associated with recovery from acute severe asthma. These results suggest that altered T-cell cytokine profiles may contribute to the pathogenesis of and recovery from asthma exacerbations.     

伯氏疟原虫氯喹抗性株感染ICR小鼠脾脏树突状细胞成熟和B细胞活化

目的 研究伯氏疟原虫氯喹抗性株(RC株)和氯喹敏感株(N株)感染鼠脾脏B细胞活化与树突状细胞(DC)的关系。 方法 分别用感染N株或RC株疟原虫的红细胞(iRBC)腹腔接种感染ICR小鼠(1×10⁶个iRBC/只)。当小鼠原虫血症N株达50%～80%、 RC株达61.7%～68.4%时, 断颈处死取脾脏。 常规方法制作石蜡切片, HE染色或免疫组织化学染色, 进行组织学观察。 制作超薄切片, 透射电镜观察脾脏细胞的变化。制作冰冻切片进行免疫荧光观察。流式细胞仪分析比较B细胞和DC变化。 结果 RC株感染小鼠脾脏白髓增生明显, 抗B细胞的特异性表面分子CD45R/B220和CD19抗体同时表达阳性的B细胞在脾细胞中的百分比增加, 中、 小淋巴细胞数量增多, 在红髓内浆母细胞与成熟的浆细胞数量增多。而N株感染小鼠脾小体则以大、 小淋巴细胞为主, 生发中心不明显, 红髓可见大量的含疟原虫的红细胞、 小淋巴细胞, 而浆母细胞和其他发育期浆细胞则少见。 RC株感染小鼠脾脏内白细胞分化抗原11c(CD11c) 阳性的DC数量明显增多, 尤其动脉周围淋巴鞘T细胞区。并且这些DC表面主要组织相容性复合体Ⅱ (MHCⅡ) 类分子表达明显升高, 表明主要是成熟的DC增多。DC外形不规则, 胞质丰富, 电子密度高, 含发达的高尔基复合体和吞噬泡样结构。 结论 RC株感染小鼠脾脏成熟的DC 明显增加, 从而诱导B细胞的活化增殖。