Induction of Listeria monocytogenes infection by the consumption of ponderosa pine needles.

Congenitally athymic homozygous (nu/nu) mice were shown to be significantly more susceptible to Trypanosoma cruzi infection than their thymus-bearing heterozygous (nu/+) littermates, as measured by increased parasitemia, mortality rate, and shortened survival time. In addition, transplantation of neonatal thymus into athymic mice reestablished normal levels of resistance to T. cruzi, i.e., comparable to those of normal littermates. These results constitute conclusive evidence that host defense mechanisms active in experimental Chagas' disease are under thymic control.     

The influence of a gastrointestinal microflora on natural killer cell activity

These studies demonstrate that the natural cytotoxicity of BALB/c mouse spleen cells for 51Cr-labeled YAC-1 cells can be significantly enhanced by microorganisms in the alimentary tract. Spleen cells from germfree BALB/c mice, euthymic, athymic, or non-nude background (+/+), had natural cell-mediated cytotoxicity for YAC-1 cells. Intestinal colonization with a few (flora-defined) or many (complex flora-conventionalized) microorganisms significantly enhanced natural cell-mediated cytotoxicity of athymic and euthymic mice over their germfree counterparts. Conversely, colonization of the alimentary tract of athymic and euthymic germfree mice with a pure culture of Candida albicans or colonization with Candida and a Bacillus sp. did not enhance natural cell-mediated cytotoxic activity over germfree levels. Spleen cells from germfree athymic mice were significantly more cytotoxic than spleen cells from germfree BALB/c mice that did not carry the nude gene (ie, +/+). In the germfree or gnotobiotic state, no difference in natural killer cell activity was evident between athymic (nu/nu) and heterozygous (+/nu) littermate mice; however, athymic (nu/nu) flora-defined or conventionalized mouse spleen cells were significantly more cytotoxic for YAC-1 cells than splenocytes from flora-defined or conventionalized heterozygous (+/nu) littermates. Spleen cells from BALB/c mice that were athymic (nu/nu) and colonized with a complex microbial flora (ie, conventionalized) had the highest percentage of cytotoxicity, at three different effector to target ratios, for YAC-1 cells. These studies indicate that the intestinal microflora can alter murine natural cell-mediated cytotoxicity.     

Susceptibility of congenitally athymic (nude) mice to sporotrichosis

Congenitally athymic (nu/nu) mice were found to be more susceptible to intravenous challenge with Sporothrix schenckii than their phenotypically normal (nu/+) littermates as measured by lethality and the number of viable yeast cells in the liver 7 days postinfection. Thymus reconstitution of nu/nu mice (nu/thy) conferred a significant degree of resistance to sporotrichosis. Immunization greatly enhanced the resistance of nu/thy and nu/+ mice, but unexpectedly increased the susceptibility of nu/nu mice. The susceptibility of nonimmunized nu/nu mice and the finding that thymus transplants augmented resistance to sporotrichosis suggest that T lymphocytes are critical to host defense.     

Modulation of total IgE levels in serum of normal and athymic nude BALB/c mice by T cells and exogenous antigenic stimulation

Several different grades of T-system impairment were studied for their effects on the total serum IgE concentration in BALB/c mice. Homozygous athymic nu/nu mice and their heterozygous nu/+ littermates were compared for serum IgE levels while kept under either barrier-maintained or conventional conditions. The results show a paradox between the T-cell dependency of the IgE immune response and the increased levels of serum IgE in the absence of T cells. Both barrier-maintained and conventionalized nu/nu mice have at least twofold increased serum IgE levels as compared to nu/+ mice. With age, IgE levels increased faster and reached higher plateau values in nu/nu than nu/+ mice. Moreover, after adult thymectomy of BALB/c mice the serum IgE levels increased up to 15-fold at 4 months of age, while infusion of immunocompetent T cells in nude mice resulted in a 2- to 5-fold decrease of the IgE level.     

Chlamydia trachomatis pneumonia in the immune,athymic and normal BALB mouse.

This paper compares the histopathology of pneumonia due to murine Chlamydia trachomatis (MoPn, mouse pneumonitis agent) in susceptible athymic nude mice (nu/nu), resistant heterozygous littermates (nu/+) and very resistant immunized nu/+ mice. While all groups had an early heterophil response, successful host defence correlated with the presence of large numbers of plasma cells, lymphocytes, monocytes, and lipid laden macrophages. Reticulate bodies were seen in all groups, predominantly in type I alveolar epithelial cells. By 24 h in the immune nu/+ group, no intact organisms were visible. Optimal control of infection was thus rapid and not clearly related to heterophils. These studies show that the histopathology of chlamydial infection may be quite atypical in the immunocompromised host, mononuclear cells seem critical in host defence, and B cell activation with plasma cell infiltration is dependent on intact T cell function in this model.     

Chlamydia trachomatis pneumonia in the immune, athymic and normal BALB mouse

This paper compares the histopathology of pneumonia due to murine Chlamydia trachomatis (MoPn, mouse pneumonitis agent) in susceptible athymic nude mice (nu/nu), resistant heterozygous littermates (nu/+) and very resistant immunized nu/+ mice. While all groups had an early heterophil response, successful host defence correlated with the presence of large numbers of plasma cells, lymphocytes, monocytes, and lipid laden macrophages. Reticulate bodies were seen in all groups, predominantly in type I alveolar epithelial cells. By 24 h in the immune nu/+ group, no intact organisms were visible. Optimal control of infection was thus rapid and not clearly related to heterophils. These studies show that the histopathology of chlamydial infection may be quite atypical in the immunocompromised host, mononuclear cells seem critical in host defence, and B cell activation with plasma cell infiltration is dependent on intact T cell function in this model.     

The role of the thymus in the pathogenesis of hind-limb paralysis induced by ts1, a mutant of Moloney murine leukemia virus-TB

Newborn homozygous BALB/c nude (nu/nu) mice, their heterozygous (+/nu) littermates, and normal BALB/c (+/+) mice were infected with ts1, a paralytogenic mutant of Moloney murine leukemia virus-TB (MoMuLV-TB). Our results indicate that while infection of +/nu and +/+ mice with ts1 results in severe pathological changes in the central nervous system (CNS) and paralysis, infection of nu/nu mice results in only mild to moderate pathology within the CNS and no paralysis. On the other hand, 50% of nude mice reconstituted with T cells when infected with ts1 developed paralysis and showed more pronounced degeneration of nervous tissue than nude mice infected with ts1 alone. These observations strongly suggest that the thymus, the functional T lymphocytes, or both play an important role in the ts1-induced neurologic disorders in infected mice.     

Nephrotoxic nephritis in nude mice.

We investigated the role of T cells in the pathogenesis of murine nephrotoxic nephritis (NTN). The disease was produced by injecting congenitally athymic nude (nu/nu) mice and their normal heterozygous (nu/+) littermates with rabbit anti-rat glomerular basement membrane (GBM) antiserum. Within 2-4 weeks we noted marked thrombotic lesions and depositions of mouse IgG, IgM, C3 and rabbit IgG along the GBM in both groups of mice. There was no significant difference in the extent of glomerular involvement between the two groups of mice. We conclude that T cell immunodeficiency plays no role in the development of severe glomerular lesions in murine NTN.     

Adoptive transfer of immunity to Nocardia asteroides in nude mice.

Nude mice on a BALB/c background were adoptively transferred with unprimed spleen cells, Nocardia-primed spleen cells, or Nocardia-primed splenic T lymphocytes from syngeneic, heterozygous (nu/+) littermates. Two days later, these recipient mice and unmanipulated (control) nude mice were infected intravenously with a 50% lethal dose of Nocardia asteroides GUH-2 from an early stationary-phase culture. Antibody titers, spleen weights, percent mortality, and organ clearance of the microorganisms were measured at 3 h to 28 days after infection. Adoptively transferred nude mice had larger spleens and greater titers of anti-nocardial antibody 7 to 28 days after infection as compared with control nude mice. Adoptive transfer with either primed spleen cells or primed splenic T lymphocytes enhanced both the survival of recipient nude mice and their ability to eliminate N. asteroides from the liver and spleen. These data indicate that adoptive immunity to infection with N. asteroides can be transferred with either specifically primed spleen cells or splenic T lymphocytes. Thus, it appears that cell-mediated immunity and T lymphocytes are of uppermost importance in host resistance to nocardial infection.     

Herpetic keratitis in athymic (nude) mice.

The inflammatory response to herpes simplex virus infection of the cornea was studied in athymic nude (nu/nu) and heterozygote (nu/+) BALB/c mice. Although athymic mice were highly susceptible to HSV infection and died 13 to 17 days after corneal inoculation, they failed to develop necrotizing keratitis of the cornea. Heterozygote mice survived the initial virual infection, but many of these mice developed necrotizing keratitis and permanent corneal scarring. Light and electron microscopy showed numerous inflammatory cells (polymorphonuclear leukocytes and lymphocytes) in the corneas of heterozygote mice, but not in the athymic mice. These studies suggest that the immune system plays a dual role in herpes simplex virus infection of the cornea: protection against dissemination of the virus and immunopathogenesis of necrotizing keratitis in the cornea.     

Trichinella spiralis infection in congenitally athymic (nude) mice. Parasitological, serological and haematological studies with observations on intestinal pathology.

In six experiments the course of a Trichinella spiralis infection in congenitally athymic (nu/nu) mice and their heterozygous thymus-bearing littermates (+/nu) was followed. In the +/nu mice worms were expelled at day 10 post infection. In nu/nu mice worms remained in the intestine until the end of the observation period (83 days post infection). In testing the yield of muscle larvae in +/nu and nu/nu mice 4--5 times more muscle larvae were isolated from nu/nu mice than from infected +/nu mice. The following phenomena were observed in +/nu mice only: anti-T. spiralis antibodies detected by immunofluorescence, intestinal plasma-cell production and intestinal eosinophilia. In nu/nu mice no blood eosinophilia was observed in contrast to the induction of eosinophilia both in infected +/nu and infected nu/nu mice reconstituted with thymuses from heterozygous littermates. Intra-epithelial lymphocytes, more numerous in +/nu than in nu/nu mice, were not attracted by Trichinella antigen. The data supported the hypothesis that worm expulsion is a T cell-dependent phenomenon. Plasma cell and antibody production as well as tissue and blood eosinophilia were shown to be thymus-dependent in a T. spiralis infection.     

Bacterial translocation from the gastrointestinal tract of athymic (nu/nu) mice.

The immune system may be one host defense mechanism preventing viable indigenous bacteria from translocating from the mouse gastrointestinal lumen to the mesenteric lymph nodes, spleen, liver, or kidney. The role of T-cell-dependent immunity in preventing bacteria from translocating from the gastrointestinal tract was tested with congenitally athymic nude (nu/nu) mice, heterozygous (nu/+) mice, and thymus-grafted nude (nu/nu) mice. Viable bacteria were cultured from 50% of the mesenteric lymph nodes, spleens, livers, and kidneys of athymic (nu/nu) mice, whereas heterozygous (nu/+) mice exhibited viable bacteria in only 5.2% of these organs. Both aerobic and strictly anaerobic bacteria were cultured from these organs with Escherichia coli and Lactobacillus predominanting. Grafting thymuses to the athymic (nu/nu) mice restored their immunological responses to sheep erythrocyte antigens. The incidence of bacterial translocation from the gastrointestinal tract was reduced from 50% in the athymic (nu/nu) mice to 7.8% in the thymus-grafted (nu/nu) mice. Thus, T-cell-dependent immunity restored by thymic grafts inhibited the translocation of certain indigenous bacteria from the gastrointestinal tract to the spleen, liver, and kidney in nu/nu mice.     

Heightened Resistance of Athymic, Nude (nu/nu) Mice to Experimental Pseudomonas aeruginosa Ocular Infection

BALB/c-derived athymic, nude (nu/nu) mice exhibited a heightened natural resistance to experimental corneal infection with Pseudomonas aeruginosa when compared with their heterozygote (nu/+) littermates. Stereomicroscopic examination of the eyes of nu/nu mice 24 h after corneal trauma and topical bacterial application revealed slightly cloudy corneas (iris visible), whereas nu/+ littermate corneas were opaque (iris not visible). Nu/+ mice failed to resolve the infection, and endophthalmitis and shrinkage of the infected eye occurred in these mice within 2 weeks after experimental Pseudomonas infection, as in the parent BALB/c strain. However, nu/nu mice, similarly infected, resolved the infection within 24 h and never exhibited full corneal opacity or eye shrinkage. Histological examination of the corneas of nu/nu mice 24 h after experimental wounding and bacterial application demonstrated subepithelial capillaries and a few polymorphonuclear neutrophils (with numerous intracellular bacteria) in the central cornea. In contrast, the equivalent corneal areas of infected nu/+ littermates, examined similarly, showed a more striking neutrophilic response (but with few intracellular bacteria) to similar bacterial infection, as well as a lack of blood vessels within the central cornea. The central corneas of uninfected and saline control nu/nu mice also were observed. This area in nu/nu mice exhibited an infrequent polymorphonuclear neutrophil (with no intracellular bacteria) and capillaries similar in size and location to those described for experimentally infected nu/nu mouse corneas. Untreated and saline control nu/+ mice, on the other hand, lacked both vessels and polymorphonuclear neutrophils in the central cornea.     

Role of T-lymphocytes in production of antibody to antigens of Rickettsia tsutsugamushi and other Rickettsia species.

The requirement of thymus-dependent lymphocytes for antibody production to Rickettsia tsutsugamushi, Rickettsia akari, Rickettsia conorii, and Rickettsia typhi was investigated by comparing antibody production in athymic (nu/nu) or thymus-bearing BALB/c mice. Athymic BALB/c mice produced antibody after infection with R. akari, R. conorii, and R. typhi as measured by indirect fluorescent antibody titration or radioimmunoassay. Antibody production in these mice was a great or greater than in the thymus-bearing mice and demonstrated similar kinetics. In contrast, athymic BALB/c mice infected either intraperitoneally or subcutaneously with the Gilliam strain of R. tsutsugamushi failed to produce demonstrable antibody. The requirement of thymus-dependent lymphocytes for antibody production to R. tsutsugamushi was further suggested by the demonstration of antibody production after transfer of immune thymus-dependent lymphocytes to athymic mice and the demonstration of R. tsutsugamushi-specific T helper cells in immune thymus-bearing mice. The antibody produced in athymic mice after infection with R. akari, R. conorii, and R. typhi was predominantly immunoglobulin M, based on isotype-specific radioimmunoassays and sucrose gradient fractionation. Furthermore, the antibody produced by athymic mice in response to R. akari infection reacted with a carbohydrate-containing outer membrane component.     

Effects of cyclophosphamide on the in vivo response of outbred athymic (nude) mice to a thymus-independent antigen (DNP-AGG-Ficoll).

Both nude mice (nu/nu) and their heterozygous littermates (nu/+) were injected with a single IP dose of 300 mg cyclophosphamide (CY)/kg. CY is a known immunosuppressive agent, which affects primarily B lymphocytes. Immunization with the thymus independent antigen DNP-AGG59-Ficoll after CY treatment disclosed that restoration of the primary direct PFC response occurred more rapidly in nude mice than in nu/+ mice. However in these same experiments, the primary indirect PFC response, recovered earlier in nu/+ mice than in nude mice. After CY treatment, secondary indirect PFC responses were delayed in both nude and nu/+ mice, but the greatest effect was seen in nude mice. The data suggest that the presence of T cells has little if any influence on the recovery capacity of those B cells which are destined to become direct PFC. However the recovery of B cells which are destined to produce indirect PFC responses is facilitated by the presence of T cells.     

Mouse model for Pneumocystis carinii pneumonia that uses natural transmission to initiate infection.

Animal models for Pneumocystis carinii, for the most part, have been limited to immunosuppressed rats and ferrets, while a dependable mouse model has been more difficult to develop. A P. carinii mouse model has now been established with several strains of mice, including C3Heb/FeJ, C3HeN, BALB/c, DBA/2N, and BALB/c nu/nu (athymic). In lieu of using invasive methods for initiating P. carinii infections, mice harboring P. carinii transmitted the disease to mice without latent infection via short-term cohabitation. After the exposure period, the seed mice were sacrificed to confirm the presence of acute P. carinii pneumonia. Acute infections in recipient mice developed at approximately 7 to 8 weeks, while control unseeded littermates remained uninfected. All recipient mice and their littermates were maintained in isolation hoods to eliminate the possibility of exposure to other sources of P. carinii. This approach allows investigators to consistently transmit P. carinii to mice and to select the strain of mouse desired for use in a particular study. The results presented here suggest that more attention should be given to the potential for patient-to-patient transmission of P. carinii in immunocompromised patients such as those with AIDS.     

Role of activated macrophages in resistance of congenitally athymic nude mice to hepatitis induced by herpes simplex virus type 2.

Congenitally athymic nude (nu/nu) mice of a BALB/c genetic background were found considerably more resistant to the induction of focal necrotic hepatitis by herpes simplex virus type 2 (HSV-2) tha, were phenotypically normal littermates (nu/+) or BALB/c mice. The augmented resistance was age dependent, as it was only manifested in mice from 4 to 5 weeks of age. Studies of the course of infection showed that nude mice were able to restrain virus multiplication in the liver far better than normal mice in the early phase of infection. However, they seemed inferior to normal mice in eliminating the infectious process. In vitro investigation of peritoneal macrophages revealed that macrophages from 6-week-old nude mice exhibited accelerated spreading and were three times as restrictive in the replication of HSV-2 as macrophages from normal mice. However, no difference was found in the efficiency of adsorption/phagocytosis between macrophages from nude and normal mice. The increased resistance of nude mice could be abolished by blockade of the microphage function of the mice by silica. Nude mice reconstituted at birth with thymus cells were just as susceptible to infection as normal mice. These data suggest that the increased resistance of nude mice to HSV-2 hepatitis is due to the presence of nonspecifically activated macrophages before infection.     

Experimental pyelonephritis. The effect of T-cell deficiency on the course of hematogenous enterococcal pyelonephritis in the mouse

The course of experimental hematogenous pyelonephritis due to Streptococcus faecalis was compared in athymic (nu/nu) mice and euthymic (nu/+) littermates. Up to 7 weeks following infection, there were no significant differences in renal microbial populations. At 63 and 107-131 days there was significant escalation of infection in nu/nu mice, while the nu/+ mice were decreasing their infections. There was no increase in gross abscess formation in nu/nu mice, but in late stages significantly more gross scarring occurred in nu/nu as compared with nu/+ mice. Microscopically there was also greater scarring in nu/nu mice late in the disease, except for calyceal lesions. The data suggest that immunologic factors (T cells) are involved in the pathogenesis of chronic pyelonephritis.     

Experimental Q fever infection in congenitally athymic nude mice.

Congenitally athymic nude (nu/nu) mice and their phenotypically normal (nu/+) euthymic littermates were exposed to Coxiella burnetii administered as small-particle aerosols. After challenge, both strains of mice became infected, as characterized by rickettsemia, viable rickettsiae in the spleen, and serological conversion. The major difference noted was that euthymic animals had cleared rickettsiae from peripheral circulation and the spleen within 14 days. In contrast, rickettsiae were detected and isolated from spleen and blood of athymic mice through 60 days.     

Salmonella typhimurium aroA, htrA, and aroD htrA mutants cause progressive infections in athymic (nu/nu) BALB/c mice.

Athymic (nu/nu) BALB/c mice and their euthymic (nu/+) littermates were inoculated intravenously with live attenuated vaccine strains of Salmonella typhimurium. All strains caused progressive infections in the athymic mice but not in their euthymic littermates. Athymic mice given strain SL3261, an aroA derivative of SL1344, in doses between log 4.7 and 5.7 CFU were all severely ill and were killed by weeks 4 to 5. Athymic mice given log 4.7 CFU of a derivative of S. typhimurium C5 carrying a mutation in htrA, encoding a stress protein, were ill and were killed by week 7 in one experiment but survived to week 13 in another. Athymic mice given log 4.6 CFU of a C5 aroD htrA double mutant were ill and were killed at week 7. Athymic mice given SL3261 had high bacterial counts in the reticuloendothelial system at 4 weeks. Athymic mice given SL3261 or C5 htrA made immunoglobulin G3 (IgG3) (and to a lesser extent IgM) antibody to lipopolysaccharide (LPS), whereas euthymic mice made IgM, IgG1, IgG2a, IgG2b, and IgG3 anti-LPS antibodies. The results indicate that both aroA and htrA strains will produce slow, progressively lethal infections in athymic mice, that the htrA strain is more attenuated than the aroA strain as measured by time to death in this model, and that IgG3 anti-LPS antibody alone cannot suppress the progress of infections by very attenuated strains in athymic mice.