Heligmosomoides polygyrus: influence of infection on lymphocyte subpopulations in mouse mesenteric lymph nodes

The immune response to a primary infection of Heligmosomoides polygyrus (Nematospiroides dubius) was studied by flow cytometry in three strains of mice, BALB/c, CBA, and NIH. The chief feature of the response was a pronounced increase, during the first week, in the proportion of B lymphocytes in the mesenteric lymph nodes. All three strains also showed an increase in lymph node cellularity, although this was delayed in NIH and CBA mice. Total B cell numbers thus also increased, particularly in the BALB/c and NIH strains but only in the latter was this response maintained throughout the 4-week study. Although the early changes in B cell frequency were similar in all three strains, B cell responses were greatest in BALB/c mice, and most prolonged in NIH, when they persisted into the adult phase of the infection. These features distinguished them from CBA mice, and could be associated with known variations in resistance to challenge infections. An increase in T cell numbers was delayed in comparison with the changes in the B cell population, and the ratio of 'helper' to 'suppressor/cytotoxic' T cells remained more or less constant in all three strains. There was thus no evidence for an increase in the frequency of suppressor T cells in any strain of mouse.     

Responses of inbred mouse strains to infection with intestinal nematodes

Comparisons were made of the immune and inflammatory responses of four strains of inbred mice to infection with the intestinal nematodes Trichinella spiralis and Nippostrongylus brasiliensis to determine whether genetically determined 'high responsiveness' to infection, seen most clearly in intestinal responses, is independent of the parasite concerned and necessarily correlated with protection. The time course of infection was followed by counting adult worms at intervals after infection. Mucosal mast cells and Paneth cell numbers were determined as indices of the intestinal inflammatory response. Levels of IgG2a and IgG1 antibodies and of the cytokines IFN-gamma and IL-5 released from in vitro-stimulated mesenteric node lymphocytes were measured to assess type 1 and type 2 responses. NIH and CBA mice were the most resistant to T. spiralis and N. brasiliensis respectively, resistance in each case being correlated with the most intense intestinal inflammatory responses. C57BL/10 (B10) and B10.BR were the least resistant to T. spiralis, but were as resistant as CBA to N. brasiliensis, despite their intestinal inflammatory responses to both parasites being much lower than the other two strains. Mice infected with T. spiralis made the expected switch from a type 1 (IFN-gamma) to a type 2 (IL-5) response between days 2 and 8, and there were no significant differences in levels of these cytokines between the strains. In contrast, when infected with N. brasiliensis, CBA showed an IFN-gamma response at day 4, all strains switching to IL-5 by day 8 and NIH mice releasing the greatest amount of IL-5. The results indicate that the "high responder" phenotype to intestinal nematode infection is in part determined by host characteristics, but is also determined by the parasite concerned--seen most clearly by the differences between NIH and CBA when infected with T. spiralis and N. brasiliensis. The fact that "low responder" B10 background mice were more resistant to N. brasiliensis than "high responder" NIH implies that each parasite elicits a particular pattern of protective host responses, rather than parasites being differentially susceptible to the same response profile.     

Immune responses to Trichinella pseudospiralis and Trichinella spiralis in mice

Primary infections with Trichinella pseudospiralis and Trichinella spiralis were followed in rapid- (NIH) and slow- (B10G) responder strains of mice. Expulsion of T. pseudospiralis was slower in both strains, but markedly so only in slower responder B10G mice. Blast cell activity in the mesenteric lymph nodes of the mice correlated with the expulsion patterns. In NIH mice, both parasites stimulated a strong response by day 8 of infection and activity had returned to control levels by day 11. In B10G mice, T. spiralis elicited an earlier peak response (day 12) than T. pseudospiralis (day 18), but in both, activity returned to control levels by day 21. Immunity to T. pseudospiralis and T. spiralis could be stimulated in NIH mice by prior infection with either parasite, by injection of T. spiralis larval antigen and by adoptive transfer of immune mesenteric lymph node cells taken from mice infected with either parasite. This extensive cross reactivity, and the differences seen during primary infections, are discussed in relation to the biology and specific identity of the two worms.     

Non-H-2 linked control of low versus high responses of antigen-induced lymph node cell proliferation: possible role for antigen-presenting cells.

Quantitative differences in the magnitude of antigen-induced proliferative responses of sensitized lymph node cells between low (C3H/Anf or C3H/Cr) and high (C3H/Hej or CBA/j) responder H-2k mice have been observed 1 to 2 weeks after in vivo sensitization with antigen (OVA, PPD, and GAT). We have shown that antigen presentation is less effective in the sensitized lymph node cell populations from low responder mice compared with those from high responder mice, suggesting that the number and/or functional status of antigen-presenting cells in the regional lymph nodes may be a key factor in determining the magnitude of antigen-induced proliferative responses. These data are consistent with the hypothesis that cell traffic after sensitization plays an important role in determining the immune responsiveness of lymph nodes.     

In vitro T-lymphocyte proliferative response to mouse thyroglobulin in experimental autoimmune thyroiditis

The in vitro lymphocyte proliferative response to mouse thyroglobulin (MTg) was studied in good and poor responder mice in relationship to in vivo antibody formation and thyroid infiltration. CBA(H-2^k) and BALB/c(H-2^d) mice were immunized in the hind footpads with MTg incorporated into complete Freund's adjuvant (CFA). At weekly intervals up to 28 days, groups of mice were sacrificed. Their popliteal lymph nodes were cultured in vitro for proliferative response to MTg and their antibody levels and thyroid involvement determined. In good responder CBA mice, the proliferative responses to MTg were strongest on Days 8 to 14, where they were 9- to 14-fold over control levels, depending on the day of harvest. The response declined to 2- to 4-fold over background on Days 21 to 28, although high antibody levels were present throughout this period. The proliferative response was abrogated by anti-Thy-1 treatment, indicating its dependence on T cells. In poor responder BALB/c mice, no significant proliferative responses to MTg were observed at any time, although the animals displayed moderate levels of MTg antibody. The responses to PPD, in contrast, were similar in both strains, usually being 4- to 7-fold above background. Thyroid infiltration, like the proliferative response to MTg, was observed only in CBA mice. Thus lymphocyte proliferation at 8 to 14 days represents a reliable, early in vitro correlate of autoimmune thyroiditis induced with CFA as adjuvant.     

Cellular immune responses in mice infected with the intestinal nematode Trichuris muris.

CBA and B10.BR mice show variation in immune response to the intestinal nematode Trichuris muris. CBA mice develop strong resistance, eliminating worms from the intestine; B10BR mice are permissive and develop chronic infections. It is already known that resistance and permissiveness reflect differential T helper responses. The data reported here show that resistant CBA mice express good antigen-specific lymphocyte proliferative responses to infection, whereas cells from B10.BR mice are relatively anergic, although still responsive to Concanavalin A (ConA). The possibility that the altered proliferative responsiveness seen in infected B10.BR mice reflected quantitative or qualitative changes in T helper cells was examined by comparing cytokine production and expression of cell surface markers (CD4, CD8, and CD28) in mesenteric lymph node cells and spleen cells from both strains and comparing these with the characteristics of cells from resistant CBA mice and from CBA mice that had been rendered permissive to infection by a combination of irradiation and corticosteroid treatment. As expected, cells from B10.BR mice produced high levels of interferon-gamma (IFN-gamma), whereas those from CBA mice released high levels of IL-5, whether stimulated with adult worm somatic antigens, excretory/secretory antigens, or ConA. Immunosuppressed CBA mice produced high levels of both IFN-gamma and IL-5 throughout the experiment. FACS analysis revealed a decrease of CD4+ and an initial increase in CD8+ cells in all infected mice. No major changes occurred in the relative proportion of CD28(+) cells. Further evaluation of the CD28 costimulatory molecule, measured as mean fluorescence intensity, displayed down-regulation in permissive and immunosuppressed mice. The data obtained suggest that lymphocyte unresponsiveness and permissiveness to T. muris infection may be associated with a down-regulation or an initially reduced expression of costimulatory CD28 molecules.     

Antigen-specific lymphocyte proliferative responses in inbred mice after Trichinella spiralis infection.

The in vitro antigen-specific lymphoproliferative response of spleen, mesenteric lymph node (MLN), and coeliac lymph node (CLN) cells taken from various strains of inbred mice infected with Trichinella spiralis was assessed. In most experiments cell populations were stimulated with excretory/secretory antigens (ESA) derived from adult and larval worms. Lymphoid cells collected 5-7 days postinfection were usually the most responsive to ESA as measured by [3H]thymidine uptake. Spleen cells were more responsive than either MLN or CLN cells. There was a correlation between in vitro ESA stimulation and worm rejection in strong- and weak-responder strains of mice. Spleen and MLN cells of NFS mice showed higher antigen-specific responsiveness, whereas the same cells from B10.BR (H-2k) and B10.Q (H-2q) strains of mice were less responsive. Among intermediate responder strains 2 patterns were observed. Spleen and MLN cells of BuB and DBA/1 mice responded more strongly than those of C3H mice. Dose-response experiments demonstrated that increasing the infective dose of larvae to the host usually increased subsequent in vitro antigen-specific lymphoproliferation. Furthermore, non-MHC-linked genes appear to be the primary determinant of antigen-specific T-cell-proliferative responses in inbred mice infected with T. spiralis.     

Heligmosomoides polygyrus: decreased apoptosis in fast responder FVB mice during infection

Primary infection with Heligmosomoides polygyrus in some strains of mice is chronic although fast responder mouse strains eliminate the parasite in a short period of time. The reason for the differences is unknown. In this study apoptosis, proliferation, IL-2 and IL-6 production of mesenteric lymph node (MLN) and spleen cells in vitro from fast (FVB) and slow (C57Bl/6) responder mice were compared during H. polygyrus infection. FVB cells showed decreased apoptosis, more proliferation and more cytokine production than cells from C57Bl/6 mice during infection. At the beginning of infection in C57Bl/6 mice the apoptosis of CD4(+) but not CD8(+) cells significantly increased in MLN and spleen cell cultures. Apoptosis, when the first immune signal is given by infective larvae, might play an important role in the modulation of the response in slow responder mice.     

A vaccine based on exosomes secreted by a dendritic cell line confers protection against T. gondii infection in syngeneic and allogeneic mice

Our results show that exosomes secreted by SRDC pulsed in vitro with Toxoplasma gondii-derived antigens (Exo-TAg) induced protective responses against infection with the parasite in both syngeneic and allogeneic mice. After oral infection, syngeneic CBA/J mice exhibited significantly fewer cysts in their brains and allogeneic C57BL/6 mice survived. This protection was associated with strong humoral responses in vivo in serum from both CBA/J and C57BL/6 mice, and with high levels of anti-TAg IgA antibodies in intestinal secretions from CBA/J mice alone. Furthermore, strong cellular responses in vivo were observed in both mouse models. Cellular proliferation was associated with cytokines production by spleen and mesenteric lymph node cells. The results presented here show that exosomes are nucleic acid free vesicles that are able to induce immune responses correlated with protection against parasitic infections in both syngeneic and allogeneic mice. They could constitute an efficient tool for use in vaccination and antitumor strategies based on exosomes.     

MAdCAM-1 expressing sacral lymph node in the lymphotoxin beta-deficient mouse provides a site for immune generation following vaginal herpes simplex virus-2 infection

The members of the lymphotoxin (LT) family of molecules play a critical role in lymphoid organogenesis. Whereas LT alpha-deficient mice lack all lymph nodes and Peyer's patches, mice deficient in LT beta retain mesenteric lymph nodes and cervical lymph nodes, suggesting that an LT beta-independent pathway exists for the generation of mucosal lymph nodes. In this study, we describe the presence of a lymph node in LT beta-deficient mice responsible for draining the genital mucosa. In the majority of LT beta-deficient mice, a lymph node was found near the iliac artery, slightly misplaced from the site of the sacral lymph node in wild-type mice. The sacral lymph node of the LT beta-deficient mice, as well as that of the wild-type mice, expressed the mucosal addressin cell adhesion molecule-1 similar to the mesenteric lymph node. Following intravaginal infection with HSV type 2, activated dendritic cells capable of stimulating a Th1 response were found in this sacral lymph node. Furthermore, normal HSV-2-specific IgG responses were generated in the LT beta-deficient mice following intravaginal HSV-2 infection even in the absence of the spleen. Therefore, an LT beta-independent pathway exists for the development of a lymph node associated with the genital mucosa, and such a lymph node serves to generate potent immune responses against viral challenge.     

Lymphocyte function in experimental African trypanosomiasis. VIII. Loss of suppressor T cell function in lymph nodes

The immunosuppression that occurs in mice experimentally infected with African trypanosomiasis has been examined further. In the present study we have examined lymph node cells from Trypanosoma rhodesiense-infected C57Bl/6J mice for the ability to produce mitogen induced antigen-nonspecific suppressor T cells (Ts). Inguinal, mesenteric, and brachial lymph node cells were harvested from uninfected control mice and from mice at different periods of infection. These cells were cultured with or without concanavalin A (Con A) for 48 hr to induce Ts activity. After stimulation, the control and infected lymph node cells were passed over Sephadex G-10 columns to remove suppressor macrophages that arise during the infection from Con A-induced Ts. The column passed cells were then added to normal mouse responder spleen cells in a primary in vitro antibody response culture system with sheep erythrocytes (SRBC) as antigen. The resultant plaque-forming cell responses to SRBC indicated that Ts function was not induced in infected lymph node cell populations. However, early in the infection, a stimulatory signal was provided by both the untreated and Con A-treated infected lymph node cells, which was lost in the terminal stage. Determinations of T cell subpopulations revealed that the infected Lyt 2.2-bearing subpopulation was not significantly altered from normal controls. We conclude that T. rhodesense infected mice fail to mount normal lymph node cell antigen nonspecific Ts responses and that this loss of activity may be due to an intrinsic dysfunction in the suppressor T cell population.     

Characterization of Nippostrongylus brasiliensis infection in different strains of mice

Five mouse strains, CBA/J, BALB/c, C3H/HeJ, A/J, and C57Bl/6J-bg-bg, all showed similar expulsion kinetics for Nippostrongylus brasiliensis (infective dose = 500 L3). Typically, parasite recovery was maximal on day 2 in the lungs and by day 4 in the small intestine. Few worms (less than 5% infective dose) were recovered on day 14 in all strains. These same mouse strains exhibited immune depression on day 5 of infection with mesenteric lymph node cells (MLN) showing reduced (10-30% normal) IgM, IgG, and IgA responses against heterologous antigen. The intestinal mast cell numbers and tissue histamine levels were examined in CBA/J mice. Mast cell numbers increased (normal = less than 1/villous crypt unit; VCU) from day 5 and peaked on day 12 (greater than 15/VCU). Intestinal histamine levels did not completely correlate with mast cell numbers with maximum concentrations (240 +/- 73 ng/g, 2-fold over normal) reached by day 8. Histamine concentrations in the intestine returned to normal levels by day 20.     

Immunity to leprosy. II. Genetic control of murine T cell proliferative responses to Mycobacterium leprae

T cell proliferative responses to Mycobacterium leprae were measured after immunization of mice at the base of the tail with antigen and challenging lymphocytes from draining lymph nodes in culture with M. leprae. This T cell response to M. leprae has been compared in 18 inbred strains of mice. C57BL/10J mice were identified as low responder mice. The congenic strains B10.M and B10.Q were found to be high responders, whereas B10.BR and B10.P were low responders. F1 (B10.M X C57BL/10J) and F1 (B10.Q X C57BL/10J) hybrid mice were found to be low responders, similar to the C57BL/10J parent, indicating that the low responsive trait is dominant. Whereas B10.BR mice were shown to be low responders to M. leprae, B10.AKM and B10.A(2R) were clearly high responders, indicating that the H-2D region influences the magnitude of the T cell proliferative response. Gene complementation within the H-2 region was evident. Genes outside the H-2 region were also shown to influence the response to M. leprae. C3H/HeN were shown to be high responder mice, whereas other H-2k strains, BALB.K, CBA/N, and B10.BR, were low responders. Gene loci that influence the T cell proliferation assay have been discussed and were compared to known background genes which may be important for the growth of intracellular parasites. Because mycobacteria are intracellular parasites for antigen-presenting cells, genes that affect bacterial growth in these cells will also influence subsequent immune responses of the host.     

Observations on the gross changes in the secondary lymphoid organs of mice infected with Nematospiroides dubius

Gross changes in the size of the secondary lymphoid organs were studied during infection with the nematode parasite Nematospiroides dubius. In the strong responder NIH strain, the wet weight of the mesenteric lymph nodes (MLN) increased rapidly following infection with 400 larvae to peak on day 28 at approximately three times the resting weight. Enlargement of the spleens was also marked but regression to normal size took place when the MLN had achieved maximum size. In contrast in C57BL/10 mice, a slow responder strain, the enlargement of the MLN following infection was relatively slow, and there was no evidence of the regression of the spleen, once maximum enlargement had been achieved. When adult worms were removed by anthelmintic, the enlarged MLN and spleens returned rapidly to normal size. However, in mice infected with irradiated larvae (25 krad) the MLN stayed enlarged, despite the absence of adult worms but the spleens of these mice returned to normal size fairly rapidly. It was suggested that irradiated worms survive, perhaps as arrested larvae in the intestinal tissue, for a fairly long time, thereby providing a continual stimulus for the MLN.     

A vaccine based on exosomes secreted by a dendritic cell line confers protection against T. gondii infection in syngeneic and allogeneic mice

Our results show that exosomes secreted by SRDC pulsed in vitro with Toxoplasma gondii-derived antigens (Exo-TAg) induced protective responses against infection with the parasite in both syngeneic and allogeneic mice. After oral infection, syngeneic CBA/J mice exhibited significantly fewer cysts in their brains and allogeneic C57BL/6 mice survived. This protection was associated with strong humoral responses in vivo in serum from both CBA/J and C57BL/6 mice, and with high levels of anti-TAg IgA antibodies in intestinal secretions from CBA/J mice alone. Furthermore, strong cellular responses in vivo were observed in both mouse models. Cellular proliferation was associated with cytokines production by spleen and mesenteric lymph node cells. The results presented here show that exosomes are nucleic acid free vesicles that are able to induce immune responses correlated with protection against parasitic infections in both syngeneic and allogeneic mice. They could constitute an efficient tool for use in vaccination and antitumor strategies based on exosomes.     

The dynamics of trickle infections with Heligmosomoides polygyrus in syngeneic strains of mice.

NIH, CBA, SWR and C57B1/10 mice were repeatedly infected with Heligmosomoides polygyrus, using doses of 10-50 larvae at frequencies of 2-16 days. NIH and SWR mice regulated the worm burdens at a stable dose-dependent level for a period of several weeks, following which expulsion occurred and immunity to subsequent re-infection was established. This regulation did not occur in CBA or C57B1/10 mice, and was inhibited by cortisone treatment. Evidence was found to suggest that regulation is the result of an immune response directed against the late larval stages of the parasite, shortly after their emergence into the lumen of the gut. The frequency of infection was an important factor in determining the course of infection. Frequently infected mice expelled the parasites more rapidly than mice infected with the same total number of larvae in fewer less frequent doses.     

Genetic control of eosinophilia in parasitic infections: Responses of mouse strains to treatment with cyclophosphamide and parasite antigen

, and 1988. Genetic control of eosinophilia in parasitic infections: responses of mouse strains to treatment with cyclophosphamide and parasite antigen. International Journal for Parasitology18:1077–1085. Strain-dependent variation in the capacity of inbred and congenic mice to mount an eosinophilia in response to inoculation with the antigens of Mesocestoides corti, Trichinella spiralis or with Limulus haemocyanin (LCH), following pretreatment with cyclophosphamide (CY), is described. SWR, NIH, BALB/c, C3H and SJL mice were eosinophil high responder strains whereas C57 BL/10 and CBA mice were eosinophil low responder strains. Congenic strains with the B10 background (B10.S, B10.G and B10.BR) were all low eosinophil responders, although B10.G mice showed a level of response consistently above the other B10 congenic strains. Some of the gene(s) for high responsiveness appeared to be dominant, because F(In1)hybrids between high and low eosinophil response parental strains were intermediate to high responders. The strain-dependent pattern of eosinophil responsiveness to LHC or to M. corti and T. spiralis antigens, following CY pretreatment, was similar to that obtained previously following infection with either M. corti or T. spiralis, suggesting that heterogeneity in capacity to produce eosinophils operates independently of the nature of the eliciting stimulus.     

The immune response of male DSN hamsters to a primary infection with Ancylostoma ceylanicum

The immune response of hamsters to a chronic hookworm infection has been investigated. Ancylostoma ceylanicum caused long term infections in hamsters which were associated with prominent changes in secondary lymphoid organs. The mesenteric lymph nodes and spleens increased rapidly in size stabilizing at approximately 3-4 times the weight in control animals by weeks 3-7. Cells from both the mesenteric lymph node and spleen, after an initial period of increased blast cell activity, became less reactive in the latter stages of infection. Serum antibody responses were marked, commencing in weeks 3-4 and increasing in intensity throughout the 10 week period of measurement. The results are discussed in relation to their contribution to the understanding of human hookworm infection.     

Experimental pathogenicity of a presumed monoxenous trypanosomatid isolated from humans in a murine model

Two strains of a presumed lower trypanosomatid isolated from immunocompetent and HIV-infected humans in French West Indies were investigated in vitro and in vivo in a murine experimental model. The ability of parasites to grow in vitro in bone marrow-derived macrophages and their virulence in vivo were assessed. For in vivo infection, two groups of BALB/c mice were inoculated either by the subcutaneous or intravenous route with 10(7) promastigotes at day 0. Infection was monitored by measuring parasite load in liver, spleen, foot pad, popliteal, and mesenteric lymph nodes and brain from day 7 to day 150 post-infection using a microtitration technique. Parasites multiplied in mouse macrophages in vitro. In vivo, both strains proved infective to mice and capable of visceralization and dissemination in the popliteal and mesenteric lymph nodes, liver, spleen, and even brain. Both strains elicited a strong humoral response against trypanosomatid antigen in mice, which cross-reacted with Leishmania antigen. Contrasting with the straightforward dissemination of parasites, the infection was strikingly well tolerated by the murine host with no clinical signs and minimal tissue changes around parasitized macrophage infiltrates.