The role of genetic and ecological factors in development of resistant phenotype in mice during experimental trichinelliasis

The role of genetic (genes for wool, eyes colour, X and Y chromosomes, H-2 haplotype) and ecological (contamination intensity leading to strengthening of illness) factors in forming phenotype of resistance in mice under experimental trichinelliasis is studied. The experiments have been performed on male and female mice CBA/Ca, BALB/c, C57/BL/6J, DBA/2J, C3HA/Mv, CC57BR/Mv, CC577W/Mv and hybrids /C57BL/6J x CBA/Ca/F having 19-25 g mass each, which were infected with trichinella larvae of Byelorussian laboratory "strains" in dosage of 5, 20, 35 and 70 units per 1 g body mass. The intensity of intestine invasion, the level of free histamine in the liver, the index of inhibition of spleen leucocyte migration on the 7th day and intensity of muscle invasion on the 30th day after contamination were defined. The analysis of the results of the study allowed to formulate the following points of regularity of trichinella resistance phenotype formation in mice: 1. The phenotype is formed as the result of interaction of genetic and ecological factors. 2. Mice of different genotypes form different phenotypes of resistance to trichinella. 3. Mice of the same genotypes form different phenotypes of resistance to intestine and muscle trichinella. The problems of inheritance and mechanisms of resistance are discussed.     

Differences in initial rate of intracellular killing of Salmonella typhimurium by resident peritoneal macrophages from various mouse strains

To determine the underlining mechanism of the difference in innate susceptibility of mouse strains to infection by Salmonella typhimurium, the ingestion and in vitro intracellular killing of S. typhimurium by resident peritoneal macrophages of mouse strains that differ in natural resistance to this microorganism has been studied. The results revealed that the rate constants of in vitro phagocytosis (Kph) in the presence of inactivated rabbit immune serum did not differ between macrophages of susceptible C57BL/10 and resistant CBA mice (for both strains: Kph = 0.021 min-1). The rate constant of in vitro intracellular killing (Kk) was determined 1) after in vivo phagocytosis (CBA, Kk = 0.055 min-1; C57BL/10, Kk = 0.031 min-1), 2) after in vitro phagocytosis of preopsonized bacteria (CBA, Kk = 0.020 min-1; C57BL/10, Kk = 0.012 min-1), and 3) during continuous phagocytosis in vitro (CBA, Kk = 0.029 min-1; C57BL/10, Kk = 0.013 min-1). With all three approaches, the initial rate of intracellular killing by normal macrophages of Salmonella-resistant CBA mice amounted to about 1.7 times the value found for macrophages of susceptible C57BL/10 mice (p less than 0.01). This trait difference was independent of the previous way of ingestion of the bacteria, unaffected by the kind of opsonization, and specific for S. typhimurium, because Staphylococcus aureus and Listeria monocytogenes were killed by macrophages of these mouse strains with equal efficiency (p greater than 0.50). These findings indicate that a difference in genetic background expressed in the efficacy of intracellular killing by resident peritoneal macrophages immediately upon ingestion of S. typhimurium is relevant for the innate resistance of mice against S. typhimurium.     

Influence of immunizing dose and presence or absence of adult worms on the development of resistance to Nematospiroides dubius challenge infections of mice

H-2 congenic strains expressing resistant (H-2q, H-2f) or susceptible (H-2k) haplotypes were compared for their ability to resist challenge infection with N. dubius following a 6- or 14-day ivermectin-abbreviated immunizing infection. B10.BR mice (H-2k) were considerably more resistant to infection when the priming interval was shortened from 14 to 6 days. B10.Q (H-2q) and B10.M (H-2f) mice resisted challenge regardless of which immunization regimen was used. The influence of parasite numbers on the response to challenge was studied by comparing infections in resistant DBA/1 (H-2q) and susceptible CBA/J (H-2k) mice that differ at both H-2 and non-H-2 genes. DBA/1 mice, immunized with 50 or 150 L3 of N. dubius for 14 days, resisted challenge, whereas mice receiving 300 worms did not. In contrast, CBA/J mice failed to resist challenge at all priming doses tested. When the immunizing infection was shortened from 14 to 6 days, DBA/1 mice resisted challenge regardless of priming dose and CBA/J mice resisted challenge only when the highest dose of 300 worms was used for priming. The data suggest that susceptible strains of mice may be preferentially immunosuppressed, particularly at low infective doses, and that suppression is associated with adult worms present in the lumen of the small intestine.     

Effect of Salmonella enteritidis 11RX infection on two-stage skin carcinogenesis in mice.

S. enteritidis 11RX infection inhibits the growth of a number of transplantable tumours in mice. In addition, oral infection of mice with S. enteritidis 11RX inhibits colon carcinogenesis by 1,2 dimethylhydrazine. This study has examined the effect of S. enteritidis 11RX infection on two-stage skin carcinogenesis in mice using 7,12 dimethylbenz(a)anthracene (DMBA) as initiator and croton oil as promoter. No protection was observed in either LACA or (BALB/c x C57Bl/6J)F1 mice when live 11RX was repeatedly administered i.v. during promotion. When a protein antigen extract from S. enteritidis 11RX was administered i.v. to previously immunised mice during skin carcinogenesis, significant protection was observed both in terms of the number of mice with papillomas and the number of papillomas per mouse. However, the protection was weak and transient. LACA mice were much more susceptible to skin carcinogenesis by DMBA and croton oil than were (BALB/c x C57B1/6J)F1 mice. A preliminary study indicated that BALB/c, C57B1 and CBA mice were also relatively resistant to skin carcinogensis.     

Differences in initial rate of intracellular killing of Salmonella typhimurium by granulocytes of Salmonella-susceptible C57BL/10 mice and Salmonella-resistant CBA mice

The contribution of granulocytes to differences in the innate susceptibility of mouse strains to infection by Salmonella typhimurium was assessed on the basis of the size and composition of the inflammatory exudate after i.p. injection of bacteria and the intracellular killing of the bacteria by exudate peritoneal cells and blood granulocytes of resistant CBA and susceptible C57BL/10 mice. The increase in the numbers of both peritoneal granulocytes and macrophages 24 hr after i.p. injection of various numbers of live S. typhimurium was two to four times higher in C57BL/10 mice (p less than 0.05) than in CBA mice. However, despite the larger number of phagocytes in the inflammatory exudate, the numbers of viable S. typhimurium in the peritoneal cavity 24 hr after injection was higher (p less than 0.01) in C57BL/10 mice than in CBA mice. Because the proportion of noningested bacteria was similar in the two mouse strains (less than 30%), these findings indicate a difference in the rate of intracellular killing of the bacteria by exudate peritoneal cells (greater than 75% granulocytes) of the two mouse strains. Subsequent determination of the initial rate of intracellular killing (Kk) of S. typhimurium revealed that after phagocytosis of the bacteria in vivo, exudate peritoneal granulocytes (harvested 24 hr after i.p. injection of 10(3) live S. typhimurium) of CBA mice killed S. typhimurium twice as efficiently (Kk = 0.014 min-1; p less than 0.01) as exudate granulocytes of C57BL/10 mice (Kk = 0.008 min-1) did. Similarly, the initial rate of intracellular killing of the ingested S. typhimurium by blood granulocytes of CBA mice (Kk = 0.017 min-1) was two times higher (p less than 0.01) than that of C57BL/10 mice (Kk = 0.007 min-1). These findings may be specific for S. typhimurium, because L. monocytogenes were killed with equal efficiency by exudate granulocytes and blood granulocytes of these mouse strains (p greater than 0.20). The results of the present study are relevant with respect to the innate resistance of mice to S. typhimurium, particularly during the initial phase of infection when the inflammatory exudate contains predominantly granulocytes.     

Strongyloides ratti: Susceptibility to infection and resistance to reinfection in inbred strains of mice as assessed by excretion of larvae

Eleven inbred strains of mice, and one outbred strain, were infected with Strongyloides ratti and larvae in the faeces were quantitated. Three strains, C57B1/6, CBA and BALB/c mice were susceptible to infection while other strains demonstrated negligible infections as assessed by this method. Larvae were first seen in the faeces on day 5, peak levels were reached on days 6 and 7, and excretion ceased 10 days after infection. Factors influencing intensity of larval excretion were examined in C57B1/6 mice. Young mice (1 month of age) were found to be more susceptible to infection than 2 and 6 month old animals. Male mice were much more susceptible to infection than female animals. There was a direct relationship between the number of S. ratti injected and the number of larvae excreted over the range 200–1600 larvae; subsequent increments in dose of injected larvae failed to increase the larval output. Infection by the percutaneous route resulted in a heavier infection than did subcutaneous injection. Previous exposure to S. ratti induced a profound resistance to reinfection. It is suggested that S. ratti infections of C57B1/6 and CBA mice provide a useful model for the investigation of factors influencing the host-parasite relationship in strongyloidiasis.     

Nematospiroides dubius: genetic control of immunity to infections of mice

Inbred strains of mice differ in their susceptibility and resistance to challenge infections with Nematospiroides dubius. In our studies, F1 hybrid mice from resistant SJL and susceptible CBA parents were resistant to N. dubius challenge infections. Only 22% of backcrosses to SJL were susceptible while backcrosses to CBA had a wide range of susceptibility. Male mice were more susceptible than female mice. In another experiment, inbred strains of mice were compared in their ability to resist N. dubius challenge infection: SJL and A.SW (H-2s) mice became resistant after one immunizing infection, A, A/He (both H-2a), as well as BALB/c and DBA/2 (both H-2d) mice became resistant after two immunizing infections, while C57BL/6 (H-2b), C3H/He, CBA, and AKR (H-2k) mice remained susceptible. The resistance to reinfections was characterized by reduction of worm burdens between Days 6 and 14 postinfection. It was concluded that (1) resistance to N. dubius challenge infections is inherited in a dominant fashion and that multiple genes may influence such response, which in turn might be modulated by the Y chromosome; (2) both MHC and non-MHC genes may influence, in conjunction with the number of exposures to parasite antigens, the resistance to challenge infections.     

Mouse strain variation and effects of oocyst dose in infection of mice with Eimeria falciformis, a coccidian parasite of the large intestine

Stockdale P. G. H., Stockdale M. J., Rickard M. D. and Mitchell G. F. 1985. Mouse strain variation and effects of oocyst dose in infection of mice with Eimeria falciformis, a coccidian parasite of the large intestine, International Journal for Parasitology15: 447–452. Five inbred strains of mice and three hypothymic (nude) strains were infected orally with different doses of E. falciförmis oocysts. After resolution of primary infection as determined by faecal oocyst output, mice were challenged orally with a second dose of E. falciformis. Amongst the intact mice, BALB/c proved the most resistant to primary infection, while C3H/He mice were most susceptible, in terms of faecal oocyst production. Resistance was far more dramatic in BALB/c mice given high numbers of challenge oocysts. In terms of mortality at high oocyst doses, CBA/H were the most susceptible. All of the strains of mice were highly resistant to reinfection. In the case of nude mice, BALB/c. nu/nu were more susceptible than CBA/H.nu/nu or C57BL/6.nu/nu both in terms of faecal oocyst production and mortality. Thus the most resistant inbred mouse strain (BALB/c) is the least resistant in the absence of T cells. Unlike intact mice, nude mice showed no resistance to reinfection, this result being in line with previous work on this and other Eimeria spp. in nude mice.     

Strain variation in the susceptibility and immune response to Clonorchis sinensis infection in mice

Mice have shown various susceptibility to infection by Clonorchis sinensis. To compare the intra-specific variation in the host-parasite relationship of C. sinensis, 6 strains of mice (ICR, BALB/c, C57BL/6, DDY, CBA/N, and C3H/HeN) with 3 different haplotypes were evaluated on their susceptibility. The worm recovery rate and immunological responses were observed after 4 and 8 weeks of infection with 30 metacercariae. The highest worm recovery rate was observed as 20.7% in the C3H/HeN strain after 4 weeks of infection along with histopathological changes. The rate was 10.0% in C57BL/6 mice after 8 weeks. ICR, BALB/c, and CBA/N showed elevated levels of IgE at both time points when compared to the rest of the strains. The serum IgG1 and IgG2a levels were elevated in most of the strains; however, the C57BL/6 strain showed a lower level of IgG2a that indicated the IgG1 predominance over IgG2a. The production of IL-4 after concanavalin-A stimulation of splenocytes slightly increased among the mouse strains except C3H/HeN after 4 or 8 weeks of infection, but each strain produced high levels of IFN-γ after 8 weeks, which implied mixed Th1/Th2 responses. ICR, DDY, CBA/N, and C3H/HeN strains showed a significantly increased level of IL-10 after 8 weeks as compared to C57BL/6. All of the strains showed an increased level of IL-13 and suggested fibrotic changes in the mice. In conclusion, mice are insusceptible to infection with C. sinensis; however, the C57BL/6, BALB/c and ICR strains are relatively susceptible after 8 weeks of infection among the six strains. Worm expulsion may be one of the causes of low susceptibility of C3H/HeN mice strain at the 8th week. Elevated IgE, IFN-γ, and IL-13 of infected mice suggest both Th1 and Th2 responses that may be related to the low host susceptibility.     

A Staphylococcus aureus mouse keratitis topical infection model: cytokine balance in different strains of mice

Staphylococcus is a leading cause of the potentially blinding disease microbial keratitis. Even with the use of antibiotic therapy, the host inflammatory response continues to damage the cornea, which may lead to blindness. Manipulation of the host response may help improve patient outcome from this devastating disease. We aim to understand the contribution of the host response to Staphylococcus aureus infection. A S. aureus keratitis mouse model was developed in both C57BL/6 and BALB/c mice using two different strains of S. aureus (8325-4 and Staph 38). Twenty-four hours postinfection, mice were killed and eyes were harvested for enumeration of bacteria, polymorphonuclear leucocytes, chemokines and cytokines. The laboratory strain 8325-4 was not as virulent as the clinical isolate Staph 38. In vitro data showed a 250-fold increase in invasion of human corneal epithelial cells by Staph 38 compared to 8325-4. BALB/c mice were susceptible to S. aureus infection whereas C57BL/6 mice were resistant. The resistant C57BL/6 mice were polarized towards a Th2 response, which may be protective for these mice. IL-4, IL-10 and IL-6 were elevated significantly in C57BL/6 mice infected with Staph 38 (P < 0.05). Macrophage inflammatory peptide (MIP)-2 was also significantly elevated in C57BL/6 mice (P < 0.001). The susceptible BALB/c mice had a muted cytokine response, which suggests that S. aureus might be 'walled off' during infection and might avoid host defences. IL-4, IL-10 and IL-6 cytokines may be protective during Gram-positive corneal infection and therefore may be useful for adjunct therapies in the treatment of this disease.     

Gene dose effects in Ir gene-controlled systems.

(B10.A x B10.S)F1 hybrid mice produce lower levels of anti-GL phi antibody than B10.S(9R) and B10.HTT mice. To determine whether this difference is due to a gene dose or a cis-trans effect, [B10.S(9R) x B10.S(8R)]F1 mice were immunized with GL phi. These mice carry one dose of the responder Ir gene alleles in the cis position whereas the recombinant B10.S(9R) and B10.HTT mice carry two doses of the relevant genes. Both (B10.A x B10.S) and [B10.S(9R) x B10.S(8R)] F1 mice produced comparably lower amounts of antibodies as compared to the recombinant strains. The data therefore demonstrate that gene dose and not cis-trans effect accounts for the differences between F1 and recombinant strains in their antibody response to GL phi controlled by complementary Ir genes.     

Marked difference in sensitivity to gamma-ray-induced cataract between BALB/c and CBA-C3H strain mice]

Nineteen BALB/c, 14CBA/KI, 12C3H/HeJ and 15 (CBA/Kl x C3H/HeJ) F1 female mice were irradiated with 850 rad gamma-rays and transferred with 10(7) syngeneic bone marrow cells 24 hrs later. The occurrence of cataract was examined in these animals. All the BALB/c mice showed visible lens opacification in both eyes between 113 and 149 days after irradiation. All the animals were autopsied 6 months after irradiation and examined for opacification of their lenses. The proportion of opaque lenses was 100, 7.1, 16.7 and 0% in BALB/c, CBA/Kl, C3H/HeJ and (CBA/Kl x C3H/HeJ) F1 mice, respectively. The results indicate that BALB/c mice are much more sensitive to radiation-induced cataractogenesis than CBA and C3H mice.     

Lethality in LPS-induced endotoxemia in C3H/HeCr mice is associated with prevalence of proinflammatory cytokines: lack of protective action of lactoferrin

C3H/HeCr mice are more susceptible to infection compared with other strains. Lactoferrin (LF), a protein involved in innate defense, was shown to protect mice against lethal endotoxemia. In this investigation we attempt to explain the cause of increased susceptibility of C3H/HeCr mice to LPS and lack of protective LF action in these mice. We found that C3H/HeCr mice produced up to 5-fold more serum TNFalpha and 66% higher IFNgamma levels in response to i.v. LPS injection than the control, CBA strain. 24 h pretreatment of C3H/HeCr mice with LF did not cause inhibition of the LPS-induced TNFalpha serum levels, whereas in CBA mice LF significantly decreased TNFalpha level. IL-6 serum levels, in turn, were lowered in C3H/HeCr mice but elevated in CBA mice. That differential regulation of cytokine production by LF in C3H/HeCr mice paralleled a decreased survival after lethal LPS injection - 10% vs. 60% in control, PBS treated mice. In addition, determination of colony forming units (CFU) in livers and spleens after administration of 10(8) Escherichia coli revealed that pretreatment of CBA mice with LF caused a marked reduction of CFU in these organs, whereas in C3H/HeCr mice the changes were insignificant. These results indicate that the altered TNFalpha/IL-6 ratio in C3H/HeCr mice, as compared to control CBA mice, as well as the increased IFNgamma level, may be responsible for the increased susceptibility to endotoxemia in that substrain. We also suggest that an association exists between the LF protective effect against endotoxic sequelae and the insult-induced systemic immune response.     

IL-1 receptor-associated kinase 1 mediates protection against Staphylococcus aureus infection

The interleukin-1 receptor-associated kinase-1 (IRAK-1) mediates signal transduction from Toll-like/IL-1/IL-18 receptors. Though a critical protective role against Staphylococcus aureus infection has been previously attributed to myeloid differentiation factor 88 (MyD88) and IRAK-4, both also involved in TLR/IL-1/IL-18 signaling, the role of IRAK-1 is unknown. IRAK-1-deficient (IRAK-1-/-) and wild-type mice were inoculated i.v. with 2 x 10(7) or 1 x 10(6) S. aureus per mouse to evaluate the role of IRAK-1 in S. aureus sepsis. Since IRAK-1 transduces IL-1R signals, IL-1R-/- mice were also included in experiments. IRAK-1-/- mice are susceptible to a high dose of S. aureus compared to wild-type controls. In contrast to the high mortality and extensive weight loss seen in IL-1R-deficient mice in response to 1 x 10(6) S. aureus, IRAK-1-/- mice are resistant to this low dose of S. aureus. Thus IRAK-1 plays an important role in the host response to staphylococcal sepsis.     

Genetic susceptibility to chlamydial salpingitis and subsequent infertility in mice.

Groups of mice from genetically defined inbred strains were infected genitally with a pathogenic human strain of Chlamydia trachomatis and their subsequent fertility was compared. The CBA, C3H (H-2o) and C3H/He-mg (H-2k) mice were less fertile than control mice, at least up to 6 months after infection. In contrast, fertility was not impaired in BALB/c mice or in congenic BALB/K mice, which had the H-2k haplotype. Reduced fertility was paralleled by the extent of histological oviductal inflammation in mice of each strain. No salpingitis was seen 21 days after infection in the BALB strains, but lesions were apparent in CBA and C3H strains up to about 70 days after inoculation and these sometimes developed into hydrosalpinges. These results indicate that susceptibility to chlamydial salpingitis and subsequent infertility is under genetic control. This control was not simply associated with the major H-2 gene complex, as mouse strains of the same haplotype (H-2k) differed in susceptibility. The fertility of BALB/c (H-2d) and BALB/K (H-2k) strains was no different from that of controls, and congenic C3H mice of differing H-2 haplotypes (H-2k and H-2o) showed reduced fertility. Although all the infected F1 (BALB/K x C3H/He-mg) mice produced litters at the same rate as untreated controls, the litters were considerably smaller. This was due to the occurrence of unilateral pregnancies in the mice inoculated under the ovarian bursae and possibly also to early fetal death in mice inoculated directly in the uterus. These findings emphasize the importance of early diagnosis and treatment of infection of the lower genital tract of women.     

Resistance of C57BL/6 mice to amoebiasis is mediated by nonhemopoietic cells but requires hemopoietic IL-10 production

Resistance to intestinal amoebiasis is mouse strain dependent. C57BL/6 (B6) mice clear Entamoeba histolytica within hours of challenge, whereas C3H and CBA strains are susceptible to infection and disease. In this study, we show using bone marrow (BM) chimeric mice that mouse strain-dependent resistance is mediated by nonhemopoietic cells; specifically, B6 BM --> CBA recipients remained susceptible as measured by amoeba score and culture, whereas CBA BM --> B6 recipients remained resistant. Interestingly, hemopoietic IL-10 was required for maintaining the resistance of B6 mice, in that B6 IL-10-deficient mice and IL-10(-/-) BM --> wild-type recipients, but not IL-10(+/+) BM --> IL-10(-/-) recipients, exhibited higher amoeba scores than their wild-type controls. Additionally, C57BL/10 IL-10(-/-)Rag2(-/-) mice exhibited diminished amoeba scores and culture rates vs IL-10(-/-) mice, indicating that lymphocytes potentiated the susceptibility of IL-10-deficient mice. We conclude that nonhemopoietic cells mediate the natural resistance to intestinal amoebiasis of B6 mice, yet this resistance depends on hemopoietic IL-10 activity.     

Genetics of resistance to the African trypanosomes. V. Qualitative and quantitative differences in interferon production among susceptible and resistant mouse strains

The induction of interferon (IFN) was examined in different inbred mouse strains infected with Trypanosoma brucei rhodesiense. Relatively susceptible C3HeB/FeJ mice that do not exhibit variant-specific immunity or control parasitemia did not exhibit detectable IFN throughout the infection. Relatively resistant B10.BR mice that exhibit variant-specific immunity and control the first peak of parasitemia exhibited detectable IFN at two intervals. The appearance of IFN in B10.BR serum first coincided with the onset of the parasitemia 4 days after infection and then disappeared; this IFN peak was predominantly IFN-alpha/beta. The second time of appearance coincided with high titers of antibody and remission of the parasitemia. This IFN was predominantly IFN-gamma. Intermediately susceptible CBA/J mice also exhibited two detectable peaks of IFN; the first IFN-alpha/beta peak coincided with the onset of the parasitemia as in B10.BR mice. The second peak of IFN in the serum of CBA mice, however, was delayed in appearance and lower in concentration compared with B10.BR mice. This peak was characterized as being predominantly IFN alpha/beta. BALB/c mice (also intermediately susceptible) did not exhibit a first peak of IFN-alpha/beta production, but the second peak of IFN-alpha/beta production was similar to that seen in CBA mice. In contrast to infected mice, IFN was induced in both susceptible (C3H) and resistant (B10.BR) mice after immunization with glutaraldehyde-fixed trypanosomes or after chemotherapy of infection. We conclude that both the levels of IFN as well as the type of IFN induced during infection with T. b. rhodesiense depend upon the genetic background of the mouse strain infected. The induction of IFN-gamma in mice of the C57BL background may be linked functionally to more effective parasite control and to the presence of an effective immune response to T. b. rhodesiense.     

SJL/J Mice Are Highly Susceptible to Infection by Mouse Adenovirus Type 1

Mouse adenovirus type 1 (MAV-1) targets endothelial and monocyte/macrophage cells throughout the mouse. Depending on the strain of mouse and dose or strain of virus, infected mice may survive, become persistently infected, or die. We surveyed inbred mouse strains and found that for the majority tested the 50% lethal doses (LD(50)s) were >10(4.4) PFU. However, SJL/J mice were highly susceptible to MAV-1, with a mean LD(50) of 10(-0.32) PFU. Infected C3H/HeJ (resistant) and SJL/J (susceptible) mice showed only modest differences in histopathology. Susceptible mice had significantly higher viral loads in the brain and spleen at 8 days postinfection than resistant mice. Infection of primary macrophages or mouse embryo fibroblasts from SJL/J and C3H/HeJ mice gave equivalent yields of virus, suggesting that a receptor difference between strains is not responsible for the susceptibility difference. When C3H/HeJ mice were subjected to sublethal doses of gamma irradiation, they became susceptible to MAV-1, with an LD(50) like that of SJL/J mice. Antiviral immunoglobulin G (IgG) levels were measured in susceptible and resistant mice infected by an early region 1A null mutant virus that is less virulent that wild-type virus. The antiviral IgG levels were high and similar in the two strains of mice. Taken together, these results suggest that immune response differences may in part account for differences in susceptibility to MAV-1 infection.     

Genetic control of allogenic inhibition of hematopoietic stem cells]

Adult mice of C57BL/6, CBA (CBA X C57BL/6) F1, (CBA X C57BL/6) F2, F1 X CBA and F1 X C57BL/6 strains were lethally irradiated and reconstituted with a constant dose of 3-10(5) C57BL/6 bone marrow cells. At the 9th day after the bone marrow transplantation the colony count was performed in spleen of irradiated recipients. In the spleen of F1, CBA and C57BL/6 mice were registered low (0--8, intermediate (6--18) and high (22-40) numbers of colonies respectively. The segregation ratios in F2 progeny were close to 2 (low): 1(intermediate): 1(high). The segregation ratios in backcross (F1 X CBA) were close to 1(low): 1(intermediate)numbers of colonies. Backcrosses (F1 X C57BL/6) were distributed to low and high numbers of colonies with the ratio 1:1. The number of spleen colonies of males and females was the same in all segregating progeny. The results of hybrid analysis suggest that a single pair of allelic genes is involved in genetic control of allogenic inhibition, and that the resistance (manifestation of inhibition) to C57BL/6 stem cells is conferred by the dominant allele.