IL-2 production, IL-2 receptor expression, and IL-2 responsiveness of spleen and mesenteric lymph node cells from inbred mice infected with Trichinella spiralis

The in vitro production of IL-2 and IL-2R expression by lymphoid cells of inbred mice of strong (NFS), intermediate (C3H), or weak (B10.BR) in phenotype of Trichinella spiralis (TS) rejection was measured during a primary infection. Maximum production of IL-2 by spleen and mesenteric lymph node (MLN) cells occurred at 5 days postinfection. Cell depletion experiments demonstrated that Lyt-1.2+ T cells were predominantly responsible for in vitro IL-2 production. Cells from strong-responder NFS mice produced more IL-2 than cells from intermediate-responder C3H or weak-responder B10.BR mice. Similarly, after TS infection, NFS mice had significantly more IL-2R expressing MLN cells than B10.BR or C3H MLN cells. All mouse strains displayed a dose-dependent increase in in vitro IL-2 production after infection with 100 to 800 TS. This effect was most pronounced in NFS mice. Limiting dilution analysis of day 5 infected MLN cells demonstrated that the frequency of TS-reactive CD4+ cells was threefold higher in NFS mice than B10.BR and fourfold higher than in C3H mice. Finally, MLN cells taken from infected NFS mice responded to an exogenous source of IL-2, whereas MLN cells from infected C3H or B10.BR mice were unable to do so. We conclude that strong responsiveness in parasite rejection may be related to the amount of IL-2 produced as well as to the capacity of the lymphocytes of each mouse strain to respond to IL-2. Although these differences help explain the strong rejection phenotype of NFS mice, they fail to separate C3H and B10.BR mice where TS-responsive CD4+ precursors, IL-2 production, and dose responsiveness are all lower for the intermediate phenotype (worm rejection) C3H than the weak phenotype B10.BR mice.     

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.     

Genetic analysis of expulsion of adult Trichinella spiralis in NFS, C3H/He, and B10.BR mice

The genetics of T. spiralis rejection from the intestine was examined in inbred mice belonging to three phenotypic categories of expulsion: strong (NFS), intermediate (C3H), and weak (B10.BR). Experiments used various worm doses to analyze the day of worm rejection, defined as the day at which 98% expulsion of the infectious dose occurred. The F1 of NFS (strong) x B10.BR (weak) was a strong responder and the F1 of the cross C3H (intermediate) x B10.BR (weak) was intermediate. Analysis of time of rejection among offspring of the (NFS/B10.BR) x B10.BR backcross showed three segregating phenotypic categories which occurred in a ratio of 1:2:1 strong:intermediate:weak. Segregation analysis of C3H/B10.BR intercross (F2) mice produced a ratio of 3:1, intermediate:weak. The backcross C3H/B10.BR to the C3H parent produced 100% intermediate offspring and the backcross to the B10.BR parent segregated in a 1:1 ratio of intermediate:weak. Taken together the results of both sets of crosses demonstrated that strong responsiveness was a consequence of the additive effects of two dominant genes; either gene by itself conferred intermediate responsiveness. The additive nature of these dominant genes suggested that two distinct processes each lead to the expression of worm expulsion that is phenotypically intermediate and kinetically identical.     

Trichinella spiralis: evidence that mice do not express rapid expulsion.

The rapid expulsion of Trichinella spiralis by mice of a variety of inbred and F1 mouse strains was examined. Mice were reinfected once with T. spiralis during and immediately after the natural termination of a primary infection and worm rejection was measured less than or equal to 24 hr after the challenge. The results showed that the challenge (super)infection was consistently rejected by all mouse strains before rejection of the adult worms from the primary infection commenced. Rejection of the challenge infection began at different times after the primary infection with NFS (2 days) less than C3H less than or equal to B10.Q approximately B10.BR (greater than 5 days). In all strains, rejection of the challenge infection preceded adult worm rejection from the primary infection by 5-8 days. At its peak, the loss of challenge worms related directly to the strength of the primary rejection process NFS greater than or equal to 98%, C3H 90-98%, and B10 mice 80-90%. Furthermore, loss of the capacity to reject the challenge followed approximately 7 days after the complete loss of the primary infection in each strain examined. Thus, the sooner worms from the primary infection were lost, the earlier the capacity to promptly reject the challenge infection disappeared. B10.Br mice still partially rejected a superinfection 35 days after the primary infection began, whereas NFS mice lost this capacity around 25 days. However, premature termination of the primary infection in B10.BR mice with methyridine at the same time that NFS mice naturally terminated their infection (15 days) abrogated the capacity of B10.BR mice to reject the superinfection at 24 days. Passive transfer of protective rat IgG monoclonal antibody to mice did not lead to rapid expulsion. Transfer of mouse immune serum to intestinally primed rats did result in rapid expulsion, suggesting that mouse antibody responses were adequate. The expression of superinfection rejection was susceptible to the administration in vivo of GK1.5, anti-mouse L3T4 antibody. The data indicate that the principal determinant of the strength, time of initiation, and longevity of rejection of a challenge infection was the response to the primary infection of that individual mouse strain. The genetic determinants of challenge infection rejection were seen to be identical to those that determined rejection of the primary infection. Since no evidence could be found to support the identity of this response with rapid expulsion, as defined in rats, a new term, "associative expulsion," is proposed.(ABSTRACT TRUNCATED AT 400 WORDS)     

Trichinella spiralis: murine strain variation in response to monoclonally defined, protective, nonstage-specific antigens

Nine hybridoma cell lines secreting monoclonal antibodies (mAbs) against Trichinella spiralis muscle larvae (ML) excretory/secretory antigens (ESA) were developed. Two mAbs, 6-D8-E3 (6D8) and 6-B1-G10 (6B1), were studied in detail. Western blot analysis using ML ESA showed that 6D8 recognized 35- and 40-kDa constituents whereas 6B1 identified a doublet of 33 kDa. However, Western blots of SDS-PAGE of crude ML homogenate showed that 6D8 identified proteins of approximately 35 and 43-60 kDa, whereas 6B1 recognized bands of 42-50 kDa. These results indicated substantial apparent MW differences between secreted and nonsecreted proteins recognized by both mAbs. Neither 6D8 nor 6B1 reacted with adult worm ESA, but both recognized antigens in aqueous extracts of homogenates of whole adult worms. Competitive inhibition experiments using ML ESA as a target demonstrated that the antigen epitopes recognized by monoclonals 6D8, 6B1, a rat mAb, 9D4, and a 37-kDa antigen previously defined were noncross-reactive. MAbs 6D8, 6B1, and 9D4 were used to isolate proteins possessing target determinants by affinity chromatography from crude ML homogenates. Each mAb isolated distinct protein species as determined by SDS-PAGE (6B1, approximately 42 kDa; 6D8, approximately 28, 37, and 61 kDa; 9D4, approximately 29, 33, 38-57, 80, and 86 kDa). NFS mice responded in a dose-dependent manner to affinity-purified antigens and were 25-fold more effective (by weight of antigen) than either C3Heb/Fe(C3H) or B10.BR mice. Immunization of mice with 6D8, 6B1, or 9D4 antigens induced strong protection against a subsequent challenge infection in NFS mice as indicated by accelerated intestinal adult worm expulsion, reduced fecundity of the female worms, and reduction of ML burden. Affinity-isolated antigens stimulated in vitro proliferation of spleen and MLN cells from immune mice; however, the mitogenic response to these antigens barely varied among NFS, C3H, and B10.BR strains.     

Evidence for differential induction of helper T cell subsets during Trichinella spiralis infection

The H-2-compatible mouse strains, AKR and B10.BR, exhibit disparate responses to infection with the parasitic nematode Trichinella spiralis. The resistant AKR mice expel intestinal adult worms faster than susceptible B10.BR mice. We tested antibody and lymphokine responses in these strains. With respect to antibody responses, the B10.BR mice had 3- to 10-fold more serum IgE and T. spiralis-specific IgG1 and IgA than AKR mice. The B10.BR mice also had greater numbers of IgG and IgA plaque-forming cells than AKR mice. In contrast, AKR mice produced T. spiralis-specific IgG2a, whereas the B10.BR mice did not. The antibody response kinetics of these strains were similar. We also analyzed lymphokine secretion after restimulating lymphocytes in vitro with T. spiralis Ag. The AKR mesenteric lymph node cells produced more IFN-gamma and less IL-4 than the B10.BR mesenteric lymph node cells. The B10.BR splenocytes produced more IL-4 than the AKR splenocytes, although splenocyte IFN-gamma production was not different. The kinetics of IL-4 production also differed between the two strains. In summary, resistant AKR mice produced more IFN-gamma and T. spiralis-specific IgG2a than susceptible B10.BR mice, which produced more IL-4, IgE, and T. spiralis-specific IgG1. Our results are consistent with differential activation of Th cell subsets in T. spiralis-infected AKR and B10.BR mice.     

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.     

Genetic control of immune responses to the 18-kDa protein of Mycobacterium leprae. Different TH1 subsets may be involved in proliferative and delayed-type hypersensitivity responses.

In vitro and in vivo responses to the 18-kDa protein of Mycobacterium leprae have been analysed in different strains of mice. Lymphocytes from BALB/cJ (H-2d), BALB.B (H-2b), B10.BR (H-2k), and B10.M (H-2f) mice primed with 18-kDa protein yielded high T cell proliferative responses, while those from C57BL/10J (H-2b) mice yielded lower responses. Both H-2 and non-H-2 genes contributed to the magnitude of responsiveness. F1 mice from high and low responder strains showed high responsiveness to the 18-kDa protein. Supernatants from lymph node cell cultures prepared from 18-kDa protein-immunised BALB/cJ, B10.BR, and C57BL/10J mice contained IL-2 but no IL-4, indicating that activated T cells from both high and low responder mice were of a TH1 phenotype. Cell cultures from low responder C57BL/10J mice produced less IL-2 than those from high responders. The low responsiveness to the 18-kDa protein in proliferative assays might be due to a low frequency of antigen-specific T cells in the C57BL/10J mouse strain. BALB/cJ, C57BL/10J, and F1 (BALB/cJ x B10.BR) mouse strains were tested for in vivo DTH reactions to the 18-kDa protein. All strains, including C57BL/10J, were high DTH responders. Although DTH effector cells and 18-kDa protein-specific proliferative T cells belong to the TH1 subset, our data comparing high and low responder status indicate that distinct TH1 subpopulations are stimulated in response to the 18-kDa protein of M. leprae.     

Heterogeneity in the immune response to serotype b LPS of Actinobacillus actinomycetemcomitans in inbred strains of mice

We investigated the heterogeneity of the humoral immune responses to whole cells and lipopolysaccharide (LPS) of Actinobacillus actinomycetemcomitans serotype b and production of cytokines in inbred strains of mice. Nine such strains were tested: A/J (H-2(a)), C57BL/6 (H-2(b)), BALB/c (H-2(d)), DBA/2 (H-2(d)), B10.BR (H-2(k)), C3H/He (H-2(k)), C3H/HeJ (H-2(k)), DBA/1 (H-2(q)) and B10.S (H-2(s)). Mice were immunized intraperitoneally with whole cells of A. actinomycetemcomitans ATCC 43718 (serotype b) in phosphate buffered saline (PBS; pH 7.2) emulsified with an equal volume of Freund's incomplete adjuvant. Serum immunoglobulin G (IgG), immunoglobulin A (IgA) and immunoglobulin M (IgM) levels against A. actinomycetemcomitans were measured by an ELISA system. ELISA analysis, using LPS fractions from serotype a, b or c strains of A. actinomycetemcomitans as the coating antigens, revealed that mice strains C3H/He, C3H/HeJ, B10.BR and B10.S had an extremely high-IgM response against serotype b LPS. High-IgM titer sera contain also elevated levels of IgA antibodies to the antigen. To compare the cytokine production among inbred mice, the amounts of interleukin-4 (IL-4), interleukin-5 (IL-5), and interleukin-6 (IL-6) released from mouse splenocytes were measured using ELISA systems specific for these cytokines. A. actinomycetemcomitans serotype b LPS stimulation induced IL-6 release from murine splenocytes of all tested strains. However, IL-4 and IL-5 were detected only in high-IgM/IgA responders to A. actinomycetemcomitans serotype b LPS, not in low-IgM/IgA responders. Thus, we found a relationship between the humoral immune response to LPS of A. actinomycetemcomitans serotype b and production of type 2 cytokines by splenocytes.     

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.     

Regulation of IFN-γ and IL-10 synthesis in vivo, as well as continuous antigen exposure, is associated with tolerance to murine skin allografts

C3H/HEJ mice are rendered hyporesponsive to multiple minor incompatible (B10.BR) skin allografts by pretreatment with irradiated B10.BR lymphoid cells injected via the portal vein, but not the lateral tail vein. As assessed by PCR with lymphocytes taken from grafted mice, or by measuring cytokines in vitro from antigen-restimulated cells, this hyporesponsiveness is associated with decreased mRNA for IFN-γ and IL-2 production, but enhanced mRNA for IL-4 and IL-10 production. In mice given B10.BR cells via the tail vein, but in addition injected every second day with anti-IFN-γ antibody, similar enhanced graft survival (with diminished IFN-γ/IL-2 and enhanced IL-4/IL-10 production) was seen. In a separate study spleen cells from pretreated mice were “parked” in lethally irradiated syngeneic mice for 21 days, along with B10.BR skin grafts to some of the recipients. Only when recipients received this reexposure to B10.BR antigen did adoptively transferred spleen cells show “persistence” of the ability to produce delayed graft rejection and preferential IL-4 production in vitro.     

Trichinella spiralis: quantitative relationships between intestinal worm burden, worm rejection, and the measurement of intestinal immunity in inbred mice

The effect of widely different doses of Trichinella spiralis muscle larvae on time to rejection of intestinal adults and on host survival was assessed in mice of the three rejection phenotypes; strong, intermediate, and weak. Rejection is weak with doses of less than 50 larvae per mouse. At these doses all mice rejected worms at a similar rate and no phenotypic variation was evident among strains. In contrast, rejection time was shortest for all strains and phenotypic variation among strains was evident in the range 50-100 muscle larvae/mouse. Above this dose the time taken to rejection increases monotonically with dose for all mouse strains examined. Despite this, the relative strength of rejection (i.e., phenotype) of a given strain of mouse was not changed at higher doses. Based on an end point of 98% rejection of the infective dose, time to rejection was predictable to +/- 1 day for all mouse strains and doses tested over the range 100-1000 worms administered. The principal reason for the increased time to complete rejection with larger worm doses was a delay in the initiation of intestinal rejection. This delay was evident above a dose of 50-100 larvae per mouse and occurred in all strains. Once begun, rejection was faster and eliminated more worms in unit time at higher doses (400-800 more) than at lower doses of worms. This appeared to be due to a stronger immune response of the host at higher doses. However, the increase in the rate of rejection was still not as great as the increase in the dose. We postulate that the delay in rejection with increased dose is due to a requirement for a "critical mass" of effectors/worm required to cause rejection. As dose increases, more time is required to reach the level at which worm rejection commences. Deaths due to higher doses of worms also occurred in a strain-specific manner and were temporally biphasic. The intestinal phase of infection produced mortality from 1 to 5 days after infection and the strongest rejection phenotype (NFS) was also the most resistant to intestinal deaths. Deaths occurring after Day 5 were due to the parenterally migrating newborn larvae. The weakest rejection phenotype, that of the B10 congenics, was also the least resistant to intestinal deaths. An experimental formula describing 98% worm rejection time with different doses was derived from the data.(ABSTRACT TRUNCATED AT 400 WORDS)     

Trichinella spiralis: Genetics of worm expulsion in inbred and F1 mice infected with different worm doses

The nematode Trichinella spiralis is rejected from the intestine at a time that is characteristic for each inbred strain of mouse. Previous work (R. G. Bell et al. 1982a) had empirically identified strong, intermediate, and weak phenotypes (NFR, $\text{C}\text{H}\text{He}$, and $\text{C57}\text{10}$ mice, respectively) in mice infected with 400 muscle larvae. It is shown that this classification applies to another eight inbred strains: SWR, $\text{DBA}\text{2}$, $\text{DBA}\text{1}$, LP, $\text{Bub}\text{Bn}$—all intermediate, and $\text{NZB}\text{BIN}$, C57L, A, and Mus molossinus—all weak. This phenotypic classification consistently applies with infections of 400–800 muscle larvae. Below doses of 300 muscle larvae, the strain designation of phenotype does not consistently apply. By this it is meant that the relative rejection rate changes for certain strains so that eventually some strains that were strong (NFR) or intermediate (AKR) responders to 400 muscle larvae become weak responders to 50 muscle larvae. Other strains increase their relative rejection time (B10 · BR, B10 · Q) while many do not change (NFS, $\text{C}\text{3}\text{Heb}\text{Fe}$, $\text{DBA}\text{2}$, $\text{DBA}\text{1}$). The phenomenon is most apparent in inbred parental strains rather than in F₁ crosses, and it represents a phenotypic variation in rejection time that is dependent on dose. It is also demonstrated that time of rejection is directly proportional to dose in all inbred and F₁ mouse strains that we have examined. Analysis of F₁ crosses shows that most have the rejection time of the strongest responding parental line, suggesting simple genetic control of strong, intermediate, and weak responses. Two F₁ crosses invalidated this theory. The $\text{DBA}\text{1}\text{×}\text{C3}\text{H}\text{He}$ (intermediate × intermediate) showed a strong response. The additive effects of parental rejection phenotype indicated that these lines could not be genetically identical for intermediate responsiveness. Similarly, the NFR (strong) × B10 · BR (weak) F₁ showed intermediate rejection, indicating partial dominance of $\text{C}\text{57}\text{B}\text{1}\text{10}$ genes over the strong responder NFR strain. Neither the primary expulsion time phenotype, phenotypic variation to low doses, or the rejection characteristics of F₁ crosses could be ascribed to genes linked to the major histocompatibility complex.     

Genetic differences in BCG-induced resistance to Schistosoma mansoni are not controlled by genes within the major histocompatibility complex of the mouse.

Induction of nonspecific resistance to Schistosoma mansoni infection after the i.v. injection of viable BCG was investigated in outbred mice and a panel of inbred and H-2 congenic strains. Significant protection was induced in CF1, A/J, C57BL/6, C57BL/10, DBA/2, C57BR, and SJL mice. BALB/c mice were not protected whereas CBA and C3H mice expressed intermediate degrees of protection. Expression of the protective phenomenon is not controlled by genes within the MHC as shown by the marked differences in response between BALB/c and DBA/2 (H-2d) as well as between C57BR and C3H (H-2k) mice. H-2 congenic strains with C57BL/10 background (B10.A and B10.D2) were high responders. BALB.B10 mice carrying the high responder (B10) MHC on the nonresponder (BALB/c) background were not protected. The degree of splenic hypertrophy did not correlate with the expression of nonspecific resistance. These results demonstrate that, in addition to controlling specific immune responses, genetic differences influence the nonspecific protective phenomena related to BCG administration as well.     

Trichinella spiralis: nonspecific resistance and immunity to newborn larvae in inbred mice

The implantation and development of intravenously injected Trichinella spiralis newborn larvae were examined in different strains of inbred mice by determining muscle larvae burden. This was compared to the numbers of muscle larvae that established after a natural infection during which a quantitative assessment of intestinal newborn larvae production was made. In most inbred strains of mice, newborn larvae do not all successfully implant in muscle. Mice of the DBA/1 strain are the most resistant to successful implantation, and C3H mice are the most permissive. This pattern is evident in the strains studied whether newborn larvae are injected intravenously or are produced by intestinal adults. Thus, after a natural infection, 100% of intestinally produced newborn larvae implanted in C3H mice, whereas in NFR 68% and DBA/1 mice 62% successfully matured in muscle. Immunity to newborn larvae could be demonstrated as early as 10 days after exposure to this stage of the life cycle. This immunity was protective against a complete challenge infection given 9 days after newborn larvae had been injected intravenously. Protection against newborn larvae was identical in male and female mice or in mice from 1 to 9 months of age. We conclude that there are two mechanisms by which mice impair newborn larvae establishment or development in muscle. The first appears to be nonimmunological (non-specific resistance), and the second is immunological. Genetically determined variation in strain-specific expression is apparent with both mechanisms. In strains displaying high intrinsic "resistance" (DBA/1), this process is likely to account for most of the 38% reduction in newborn larvae establishment in a primary infection. However, immunity against newborn larvae develops quickly enough to have a significant effect on migratory larvae in primary infections where adults persist in the intestine (e.g., the B10 congenic mice), or when high adult worm burdens delay adult worm rejection. Muscle larvae burden, therefore, reflects systemic nonspecific resistance to newborn larvae as well as immunological processes that occur in the intestine and systemically.     

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.     

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.     

Trypanosoma musculi with Trichinella spiralis or Heligmosomoides polygyrus: concomitant infections in the mouse

Inbred mice infected with Trypanosoma musculi displayed wide variations in peak blood parasitemia. The most susceptible mice were C3H and A strain, while Balb/c, C57B1/6, and the related congenic B10 strains were the most resistant. The effect of an intestinal infection with either Trichinella spiralis or Heligmosomoides polygyrus on proliferation of T. musculi was investigated. T. spiralis infections given at the same time or up to 45 days before a T. musculi infection always caused an increase in blood parasitemia in C3H mice. Maximum increases were observed when T. spiralis infections preceded T. musculi by 5-10 days. In all mouse strains examined, dual infections increased maximum parasitemia by two- to four-fold, regardless of the degree of resistance of that mouse strain to either T. musculi or T. spiralis. This suggested that the immunological "cost" of a T. spiralis infection was the same for strains that were strong or weak responders to a primary infection with T. spiralis. In contrast, infection with H. polygyrus did not promote T. musculi parasitemia over the level of a single infection. The increase in blood parasitemia in T. spiralis-infected mice was largely due to the intestinal adult worm, but migratory larvae and mature muscle larvae also stimulated increased parasitemias. The increase in parasitemia was proportionate to the dose of T. spiralis, and the sex of the host did not affect the blood trypanosome level.     

Polymorphisms in Toll-Like Receptor 4 Underlie Susceptibility to Tumor Induction by the Mouse Polyomavirus

PERA/Ei (PE) mice are susceptible to tumor induction by polyomavirus (Py), while C57BR/cdJ (BR) mice are resistant. Antigen-presenting cells from BR mice respond to the virus with interleukin-12 (IL-12) and those from PE mice with IL-10. These polarized cytokine responses underlie the development of effective antitumor immunity in BR mice and the lack thereof in PE mice. An ex vivo cytokine production assay using spleen cells from infected [PE × BR] F2 mice together with a genome-wide SNP (single-nucleotide polymorphism)-based QTL (quantitative trait locus) analysis was used to map the determinant of cytokine production to a region of chromosome 4 carrying the Toll-like receptor 4 (TLR4) gene. Genotyping of infected F2 mice showed concordance of TLR4 allele-specific DNA sequences with the cytokine profile. Cytokine responses elicited by Py are MyD88 dependent. Bacterial lipopolysaccharide (LPS), a known TLR4 ligand, induced the same polarized responses as the virus in these host strains. Spleen cells from C3H/HeJ and C57BL/10ScNJ LPS-nonresponsive mice challenged in vitro with Py showed an impaired IL-12 response but were unaffected in IL-10 production. TLR4s of strains PE and BR differ by 3 amino acid substitutions, 2 in the extracellular domain and 1 in the intracellular domain. cDNAs encoding the TLR4s signaled equally to an NF-κB reporter in 293 cells in a ligand-independent manner. When introduced into TLR2/TLR4 double-knockout macrophages, the TLR4 cDNA from BR mice conferred a robust IL-12 response to Py and no IL-10 response. The TLR4 cDNA from PE mice failed to confer a response with either cytokine. These results establish TLR4 as a key mediator of the cytokine response governing susceptibility to tumor induction by Py.