GENETIC CONTROL OF THE IMMUNE RESPONSE TO STAPHYLOCOCCAL NUCLEASE : I. IR-NASE: CONTROL OF THE ANTIBODY RESPONSE TO NUCLEASE BY THEIR REGION OF THE MOUSEH-2 COMPLEX

A number of inbred and congenic resistant strains of mice were immunized with staphylococcal nuclease (Nase). Antibody responses were measured in the sera of the animals by a sensitive method involving inhibition of enzymatic hydrolysis of DNA, High responder strains included A/J, DBA/2, BALB/c, AKR/J, C57BR, and SJL/J. DBA/1 and C57BL/6 mice were low responders. The strain distribution of anti-Nase response potential was compatible with the relevant immune response gene(s) being linked to the murine major histocompatibility complex. Linkage of this response to H-2 was demonstrated by the findings that: (a) the congenic C3H/HeJ and C3H.SW mice were respectively high and low responders; (b) the congenic lines B10.A and B10.D2 were high responders, whereas the C57BL/10 strain was a poor responder; and (c) anti-Nase response potential of F₂ progeny from DBA/1 x SJL/J matings correlated with their H-2 type. Three B10.A recombinant lines were used to map this Ir gene within H-2. B10.A(4R) was a high responder to Nase, whereas B10.A(2R) and B10.A(5R) were both low responders. We wish to propose the name Ir-Nase for the gene(s) controlling antibody responsiveness to this immunogen. Our data indicate that Ir-Nase is located within the same chromosomal segment of the H-2 complex as is Ir-IgG.     

GENETICS OF A NEW IgVH (T15 IDIOTYPE) MARKER IN THE MOUSE REGULATING NATURAL ANTIBODY TO PHOSPHORYLCHOLINE

The idiotype present on the Fab of a phosphorylcholine-binding IgA myeloma protein TEPC 15 (T15) of BALB/c origin was found in normal serum of BALB/c mice. Molecules carrying the T15 idiotype in normal serum could be adsorbed with Sepharose phosphorylcholine beads and R36A pneumococci. The T15 idiotype is absent in germ-free BALB/c but appears when the mice are conventionalized. A survey of normal sera of inbred strains for the T15 idiotype showed it to be present in BALB/c, 129, C57L, C58, and ST and absent or in low levels in CBA, C3H, C57BL/6, C57BL/Ka, C57BL/10, SJL, B10.D2, DBA/2, RIII, A, AL, AKR, NZB, and NH inbred strains of mice. The T15 idiotype is associated with some but not all strains carrying the IgC_H allotypes found in BALB/c. Linkage of genes controlling the T15 idiotype in normal serum to the IgC_H locus of BALB/c was demonstrated in F₂ progeny of a BALB/c and C57BL cross, Bailey's recombinant inbred strains, C x BD, C x BE, C x BG, C x BH, C x BI, C x BJ, C x BK, and CB20 congenic strains. Among these strains, only those possessing the IgC_H locus of BALB/c including the F₂ progeny consisting of BALB/c homozygotes and BALB/c/C57BL heterozygotes and C x BG and C x BJ recombinants showed the T15 idiotype.     

GRAFT-VS.-HOST REACTIONS IN RECIPROCAL HYBRID MICE : I. DISSOCIATION OF T-CELL ACTIVITIES IN THE MIXED LYMPHOCYTE REACTION AND TWO GRAFT-VS.-HOST ASSAYS

Spleen cells from BALB/c and C57BL/6 mice were tested for their reactivity against reciprocal hybrid tissues ((BALB/c x C57BL/6) F₁ and (C57BL/6 x BALB/c) F₁) in three assay systems: the mixed lymphocyte reaction (MLR); the Simonsen spleen-weight graft-vs.-host (GVH) assay; and a GVH mortality assay. It was shown that both F₁'s serve as equally effective stimulators of parental cells in the MLR. In the spleen-weight assay, BALB/c and C57BL/6 cells were equally active in a given host, but greater splenomegaly was observed in (BALB/c x C57BL/6) F₁ hosts regardless of the donor strain. By contrast, BALB/c cells were much less lethal than C57BL/6 cells in (BALB/c x C57BL/6) F₁ hosts than in (C57BL/6 x BALB/c) F₁ hosts, and to a lesser degree C57BL/6 cells were less lethal than BALB/c cells in (C57BL/6 x BALB/c) F₁ hosts. The possibility that modifying substances may differentially alter reactivity of parental lymphocytes and that considerations other than genotype determine the outcome of a GVH reaction are discussed in detail.     

AUTOGENOUS IMMUNITY TO ENDOGENOUS RNA TUMOR VIRUS : IDENTIFICATION OF ANTIBODY REACTIVITY TO SELECT VIRAL ANTIGENS

The viral antigenic determinants recognized in an autogenous immune response in mice against their endogenous C-type virus have been identified by SDS-polyacrylamide gel electrophoresis of immune precipitates between various sera and H³-labeled intact or disrupted AKR leukemia virus. Normal B6C3F₁ [(C57BL/6 x C3H/Anf)F₁] serum reacts with viral envelope antigens having mol wt of approximately 68,000, 43,000, and 17,000. In addition, minor reactions with viral antigens having mol wts of approximately 19,000 and 15,000 are demonstrable. The 68,000 and 43,000 mol wt antigens can be labeled with [³H]glucosamine and may correspond to the major viral envelope antigens M₂ and M₁, respectively. The antigens recognized by autogenous immune sera do not differ with respect to age of the animal, nor are they significantly different in sera from various strains of mice (BALB/c, C57BL/6, and C3H/Anf). These results suggest that the age-asociated and strain variations in the autogenous immune response, as determined by radioimmune precipitation assays against intact virus, are due to quantitative and qualitative alterations of antibody levels against common antigens.     

GENETIC CONTROL OF RESPONSES TO BACTERIAL LIPOPOLYSACCHARIDES IN MICE : I. Evidence for a Single Gene that Influences Mitogenic and Immunogenic Respones to Lipopolysaccharides

In vivo immune responses and in vitro mitogenic responses to bacterial lipopolysaccharides (LPS) have been compared in strains of C3H mice. C3H/HeJ spleen cultures did not support mitogenic responses to LPS and in vivo these mice produce low IgM responses to LPS. On the basis of these two responses, C3H/HeJ mice have been termed low LPS responders. All other strains of C3H mice tested (C3HeB/FeJ, C3H/DiSn, C3H/Str, CWB, CSW, and C3H/Sf and its H-2 congenics) are high LPS responders supporting large in vitro mitogenic and in vivo immune responses to LPS. The immune response difference between low and high LPS responders is a quantitative one. IgM responses are observed in C3H/HeJ mice in the range of 1.0–10 µg LPS. At lower and higher LPS concentrations, immune responses are not observed. In contrast, high LPS responders elicit LPS immune responses over a much wider dose range (0.1–200 µg). The ability to respond well to LPS is dominant as shown by the response of F₁ hybrid mice of low responder and high responder strains. The linkage relationships of mitogenic and immune responsiveness to LPS have been investigated in backcross (C3H/HeJ x CWB)F₁ x CWB mice. All mice that gave in vivo immune responses to LPS also supported mitogenic responses to LPS. The defect in C3H/HeJ mice that limits mitogenic and immune responsiveness to be due to a single autosomal gene which is not linked to the H-2 histocompatibility or heavy-chain allotype loci.     

Regulation of the anti-inulin antibody response by a nonallotype-linked gene

The antibody response to the inulin [(In), beta-(2 leads to 1) fructosan] determinant of bacterial levan [(BL), a beta-(2 leads to 6) polyfructosan that contains beta-(2 leads to 1) branch points] requires the presence of the a haplotype of the Igh gene complex. BALB/c (Igh a) mice immunized with BL produce IgG anti-In antibodies of a single spectrotype by isoelectric focusing analysis. C57BL/6 mice, which possess the b haplotype of the Igh gene complex and which fail to produce anti-In antibodies, nevertheless possess a gene, spectrotype regulation gene 1 (Sr-1), that regulates the isoelectric focusing (IEF) pattern of anti-In antibodies in mice of the a haplotype. Thus, the IEF patterns of anti-In antibodies of (BALB/c x C57BL/6)F1 mice and of B.C8 mice (C57BL/Ka . Igh-Ca) are considerably more complex than those of BALB/c. Backcross analysis indicates that Sr-1 is not linked to the Igh complex, the major histocompatibility complex, or to the genes that code for coat color. Studies of the heterogeneity of anti-In antibodies in recombinant inbred lines and their progeny from matings to BALB/c and C.B20 (BALB/c . Igh-Cb) suggest the existence of other regulatory genes.     

INHERITANCE OF ANTIBODY SPECIFICITY : I. Anti-(4-Hydroxy-3-Nitrophenyl)Acetyl of the Mouse Primary Response

Our data suggest that fine specificity of antihapten antibodies is a useful Mendelian marker of variable (V) genes. We found that some mouse strains (e.g., C57/BL6) consistently produced heteroclitic anti-(4-hydroxy-3-nitrophenyl)acetyl (NP) antibodies (relative affinity for related (4-hydroxy-5-iodo-3-nitrophenyl)acetyl and (4-hydroxy-3.5-dinitrophenyl)acetyl was always >2) while other strains (e.g., CBA) produced "conventional" anti-NP antibodies (relative affinities were consistently <1). 48 (CBA x C57BL/6)F₁ mice were studied and most of them had heteroclitic anti-NP antibodies. They were backcrossed to the recessive CBA parent, and 87 backcross animals were similarly tested. Those heterozygous for the C57BL/6 heavy (H)-chain allotype were similar to the C57BL/6 and the F₁ mice while mice homozygous for the CBA allotype were indistinguishable from the CBA. Such monogenic inheritance was observed only in the primary response. Predominance of allotype-linked genes in the control of the fine specificity characteristics was confirmed by immunizing selected homozygous mouse strains. These mice contained various mixtures of genes from C57BL, BALB/c, and other strains. Specificity of their anti-NP was exclusively determined by genes linked to the H-chain allotype, no influence could be attributed to other genes including the H-2-linked genes.     

CELL INTERACTIONS BETWEEN HISTOINCOMPATIBLE T AND B LYMPHOCYTES : IV. INVOLVEMENT OF THE IMMUNE RESPONSE (Ir) GENE IN THE CONTROL OF LYMPHOCYTE INTERACTIONS IN RESPONSES CONTROLLED BY THE GENE

In the present study we have asked the question of whether F₁ carrier-primed T cells can serve as helper cells for either or both parental B cells when (a) the carrier molecule employed is under genetic control such that one parental strain is a responder and the other is a nonresponder, and (b) the determinant specificity of the parental B cells being assessed is not under genetic control and bears no relationship to the specificity of the carrier molecule. Utilizing the system of immune response gene control of responses to the terpolymer L-glutamic acid-L-lysine-L-tyrosine (GLT) to which A strain mice (H-2^a) are nonresponders, whereas BALB/c (H-2^d) and (BALB/c x A)F₁ hybrids (CAF₁) are responders, these studies demonstrate that GLT-primed T cells of CAF₁ donors can provide for responder BALB/c, but not for nonresponder A/J, the required stimulus for the anti-DNP responses of DNP-specific B cells of these respective parental strains to the DNP conjugate of GLT. The implications of these findings for Ir gene function in physiologic T-B cell interactions are discussed in detail.     

RAPID VIRAL INDUCTION OF MURINE LYMPHOMAS IN THE GRAFT-VERSUS-HOST REACTION

When weanling (SJL/J x C57BL/1)F₁ hybrid mice were given five weekly-injections of small doses of viable SJL/J spleen cells, so as to induce a graft-versus-host reaction (GVHR), reticulum cell sarcomas were induced in all of the host mice by the 40th day after the first cell injection. Such tumors, on transplantation, were accepted by syngeneic (SJL/J x C57BL/1)F₁ and C57BL/1 hosts, but not by SJL/J or NZB mice. Cell-free extracts of SJL/J spleens injected into similar hybrids resulted in identical tumors in all hosts within the same period; the transplantation characteristics were also similar. Normal (SJL/J x C57BL/1)F₁ hybrids as well as similar hybrids injected with SJL/J liver or syngeneic F₁ spleen cells did not develop tumors. Cell-free preparations of eight tumors induced in F₁'s by viable SLJ/J spleen cells were injected into newborn (C57BL/1 x A)F₁ and C57BL/1 mice: tumors were induced, with seven of eight tumor preparations, with a latent period of 33–49 days. Such tumors were lymphosarcomas, and, in the case of (C57BL/1 x A)F₁ hosts, further transplantation revealed that they were antigenically C57BL/1 tumors. These experiments provide conclusive evidence for a viral etiology of GVHR-induced tumors. Furthermore, tumor induction in the GVHR does not appear to depend specifically on an immunological mechanism but is most probably due to release or activation of a sufficient quantity of oncogenic virus within a certain time period in a highly susceptible host. Comparison with radiation induction of viral leukemia in mice revealed similarities in regard to optimal host age and the spacing of administration of the tumor-inducing agent. SJL/J mice carry a type C virus which causes a high incidence of spontaneous Hodgkin-like tumors by 1 yr of age; C57BL/1 mice do not develop lymphomas spontaneously but carry a latent leukemogenic virus. Their hybrid also has a low incidence of spontaneous lymphomas. Based on the results of these and previous experiments, the viruses of these strains of mice appear to be highly synergistic in tumor induction in the GVHR. The SJL/J virus is a powerful oncogenic agent. The C57BL/1 virus may be a helper virus to the SJL/J, but is a more powerful determinant of the antigenic composition of the induced tumors. This suggests that the virus of C57BL/1 mice, when activated, is capable of controlling the C57BL/1 genome. Because of the ease and rapidity of viral tumor induction, the SJL/J and C57BL/1 strains of mice, with their F₁ hybrid, should be useful for further study of the mechanisms controlling induction of such tumors.     

ONTOGENY OF B LYMPHOCYTES : II. RELATIVE RATES OF APPEARANCE OF LYMPHOCYTES BEARING SURFACE IMMUNOGLOBULIN AND COMPLEMENT RECEPTORS

Many bursa-equivalent (B) lymphocytes of adult mice bear surface Ig and receptors for C3. The frequency of Ig-bearing cells increases rapidly immediately after birth, but these cells lack complement (C) receptors. Lymphocytes bearing C receptors are not found in the spleens of BALB/c, DBA/2, and C57BL/6 mice until 2 wk of age and do not attain substantial numbers until 3–4 wk of age. In AKR mice, a lag between appearance of Ig-bearing and complement receptor lymphocytes (CRL) is also observed but it is of much shorter duration. AKR mice have a frequency of CRL at 2 wk of age of 28% in comparison to a frequency of 4.8% for DBA/2 mice. The difference in frequency between young and adult mice and between "low" and "high CRL" strains cannot be explained by a nonspecific inability to form rosettes as similar results are obtained with soluble antigen-antibody-complement complexes. Analysis of CRL frequency in (AKR x DBA/2)F₁ mice and F₁ x parental backcross progeny suggests that two independent genes control the rate of appearance of CRL. Furthermore, the genetic difference in the ontogeny of CRL is recapitulated in the repopulation of the B-lymphocyte line in adult-irradiated mice restored with syngeneic bone marrow. Thus, the "CRL genes" described here appear to control B-cell differentiation throughout life.     

GENETIC CONTROL OF THYMUS-DERIVED CELL FUNCTION : I. IN VITRO DNA SYNTHETIC RESPONSE OF NORMAL MOUSE SPLEEN CELLS STIMULATED BY THE MITOGENS CONCANAVALIN A AND PHYTOHEMAGGLUTININ

Concanavalin A- or phytohemagglutinin-stimulated DNA synthetic responses of 1 million normal mouse spleen cells in vitro were significantly different among various inbred strains. BALB/cJ (H-2^d) responded better than C57BL/6J (H-2^b) spleen cells, and the responses of C3H/HeJ or AKR/J (both H-2^k) cells were intermediate. These responses, measured as the increment in thymidine-³H incorporation of mitogen-stimulated compared with unstimulated cultures, varied according to the number of cells cultured or the mitogen concentration. BALB/c spleens had the highest proportion of θ-positive cells, but no direct relationship between the proportion of θ-positive cells and the DNA synthetic response was observed. (BALB/cJ x C57BL/6)F₁ spleen cells responsed as well as BALB/c cells. Responses of spleen cells from (F₁ x C57BL/6) backcross littermates varied over a range equal to, or greater than, that of BALB/c and C57BL/6 cells. There was no correlation between H-2 specificity (H-2^bd or H-2^bb) or sex and the mitogen-stimulated DNA synthetic response of backcross animals. Con A- and PHA-stimulated responses of individual backcross animals were positively correlated with the level of thymidine-⁸H incorporation by unstimulated spleen cells. These results are consistent with autosomal dominant, non-H-2-linked, polygenic control of the mitogen-stimulated in vitro DNA synthetic response of mouse spleen cells.     

SYNERGY AMONG LYMPHOID CELLS MEDIATING THE GRAFT-VERSUS-HOST RESPONSE : II. SYNERGY IN GRAFT-VERSUS-HOST REACTIONS PRODUCED BY BALB/C LYMPHOID CELLS OF DIFFERING ANATOMIC ORIGIN

The capacity of cells from different lymphoid tissues obtained from Balb/c mice to produce graft-vs.-host (GVH) reactions was quantitatively determined in C57BL/6N by Balb/c F₁ hybrid recipients. Synergistic responses were observed when small numbers of cells from lymphoid tissues that were rich in GVH activity such as spleen and femoral lymph node were combined with weakly reactive thymus cells. Thymus and spleen cells obtained from 1-wk old mice were separately inactive but produced moderate GVH reactions when combined in equal proportions. GVH activity of spleen cells from mice thymectomized at 3 days of age was partially restored by the addition of small numbers of spleen or thymus cells from adult mice. Changes in ratio between the two cell populations markedly affected the degree of synergy. Synergy was not observed when Balb/c cells were combined with Balb/c x C57BL/6N F₁ hybrid cells and inoculated into C57BL/6N recipients, but was demonstrated when Balb/c and C57BL/6N cells were combined and inoculated into F₁ recipients, indicating that a genetic disposition to mount GVH reactions in both populations is required to produce synergy. The data indicate that at least two cell types are necessary for GVH reactions, and that synergy between cell populations results from favorable adjustments in the ratio between these two cell types.     

EVIDENCE FOR THE LINKAGE OF THE IGCH LOCUS TO A GENE CONTROLLING THE IDIOTYPIC SPECIFICITY OF ANTI-p-AZOPHENYLARSONATE ANTIBODIES IN STRAIN A MICE

Anti-p-azophenylarsonate (anti-Ar) antibodies elicited in all strain A/J mice tested share one or more idiotypic specificities. These specificities are also found in the anti-Ar antibodies of mice of the closely related strain, AL/N, but not in those of BALB/c mice. Anti-Ar antibodies were elicited in congenic mice in which the IgC_H locus of AL/N mice, which controls allotypic markers in the constant regions of heavy chains, had been introgressively backcrossed for nine generations onto a BALB/c background; the mice were then rendered homozygous for the AL/N allotypic determinant. On the average, these antibodies were quantitatively equivalent, with respect to content of the cross-reactive idiotype, to those of AL/N mice. This indicates that the gene controlling the idiotype is closely linked to the IgC_H locus. Since idiotype must be a function of V region sequences, the results suggest close linkage of V_H and C_H genes. The cross-reactive idiotype was found in nearly all F₁ mice (C57/BL x A/J or BALB/c x A/J) tested.     

Serum concentrations and allotypes of immunoglobulins in two lines of mice genetically selected for "high" or "low" antibody synthesis

Random-bred Swiss mice were selectively bred for 16 generations; selection was based on their agglutinin response to sheep and pigeon erythrocytes to produce a high and a low responder line. The serum levels of individual immunoglobulins differed significantly in these two lines before immunization. The differences in the levels of immunoglobulins were much more marked after immunization with pigeon or sheep erythrocytes. Greater differences between the two lines were noted in IgM and IgG levels than in IgA. Another remarkable finding was the presence of different immunoglobulin phenotypes in the two lines. The high responders were homozygous or heterozygous for heavy-chain linkage groups found separately in the prototype BALB/c and C57BL inbred strains. The low responders were homozygous for a heavy-chain linkage group not present in bred mice in the United States, but observed as a recombinant type among wild mice probably representing a crossover between the heavy-chain linkage groups of the prototype DBA/2 and NH inbred mice.     

COMPARISON OF THE IMMUNE RESPONSIVENESS OF NZB AND NZB x NZW F1 HYBRID MICE WITH THAT OF OTHER STRAINS OF MICE

The immune responsiveness of (NZB x NZW) F₁ hybrid mice (NZB/W) has been compared with that of three other strains of mice, A/J, BALB/c, and CBA/J. The antigens used included sheep red blood cells (SRBC), keyhole limpet hemocyanin (KLH), bovine serum albumin (BSA), and human γ-globulin (HGG). It was found that important strain differences existed in the amount of antibody produced, but the relative immune responsiveness depended very much upon the nature of antigen. By comparison with the other strains tested, NZB/W mice had a higher antibody production to some antigens (SRBC and BSA) but were low responders to others (KLH). Induction of unresponsiveness to HGG by treatment with ultracentrifuged HGG was studied in the strains cited above. NZB/W mice became tolerant after injection of HGG ultracentrifuged at 100,000 g for 2 hr. Similar experiments carried out with another preparation of HGG (centrifuged at 20,000 g for 30 min) failed to reveal any abnormal behavior of NZB/W mice as compared to BALB/c or A/J mice. These results do not support the concept that NZB/W mice possess a general immune hyperreactivity or a relative inability to be made tolerant to protein antigens. However, they do not rule out the possibility that these mice have a genetically determined hyperresponsiveness to some antigens, in particular to nuclear antigens.     

PRODUCTION OF RUNT DISEASE IN TOLERANT MICE BY THE INJECTION OF SYNGENEIC LYMPHOID CELLS

When chimeric A strain mice tolerant of (A x C57BL/1)F₁ hybrid skin grafts are injected with spleen cells from normal A donors the recipients develop weight loss, clinical evidence of runting, and death in some animals. Similar recipients injected with spleen cells from A strain donors immunized against C57BL/1 tissue show a more rapid onset of the runting process and increased mortality. Runting in. these experiments therefore results from an immune attack by the injected A strain lymphoid cells against the (A x C57BL/1)F₁ hybrid tissue harbored by the chimeric recipients. Since the hybrid tissues of the chimeric recipients were derived from spleen cell populations we conclude that the immunologic rejection of lymphoid and hematopoietic tissue is sufficient to cause the runting syndrome. C3H mice tolerant of A strain skin grafts because of the prior injection of viable or disrupted A strain spleen material were given 400 r of x-irradiation and an injection of C3H spleen cells. Only the chimeric C3H mice harboring viable A strain cells developed weight loss and clinical evidence of disease, showing again that runting occurs only when an attack can be made against viable lymphoid and hematopoietic tissue. Normal A strain mice injected intravenously with 850 million (A x C57BL/1)F₁ hybrid spleen cells reject hybrid skin grafts and do not develop runting, whereas the rejection of similar hybrid tissue present in chimeric A strain mice results in runting. It is concluded that runting will occur only when the immunologic attack is directed against lymphoid and hematopoietic tissue which has become established within host tissues. The possibility that runting may result from hypersensitivity reactions occurring in the lymphoid tissues is discussed.     

Genetic control of the immune response to myoglobins. Both low and high responder T cells tolerant to the other major histocompatibility complex help high but not low responder B cells

We sought to examine the role of immune response (Ir) genes in helper T cells. To eliminate allogeneic effects, we used neonatally tolerized mice. The results bear not only on the mechanism of Ir genes, but also on the development of the T cell repertoire. B 10.BR (H-2(k)) or C57BL/10 (H-2(b)) mice, which were low responders to myoglobin (Mb), were neonatally tolerized to high responder H-2(d) alloantigens, and B10.D2 mice, which were high responders to Mb, were neonatally tolerized to low responder H-2(k) or H-2(b) alloantigens. Spleen cells from these tolerized mice did not show any reactivity in mixed-lymphocyte reaction or cell-mediated lympholysis against alloantigens used in tolerization. Mb-immune F(1) B cells were helped comparably by Mb-immune tolerized low or high responder T cells. Thus, low responder T cells functioned equivalently to high responder T cells. The failure of nonimmune T cells from tolerized low responder mice to help F(1) B cells and antigen-presenting cells (APC) indicated that collaboration between B10.BR or C57BL/10 T cells and F(1) B cells was not caused by a positive allogeneic effect. Spleen cells from tolerized mice were contaminated with 2-4 percent chimeric F(1) cells, as judged by fluorescence-activated cell sorter analysis, and no F(1) alloantigens were detectable in the thymus. However, removal of chimeric F(1) T cells from the tolerized cell population by treatment with anti-H-2 and complement did not change the helper activity of tolerized low responder T cells. These data indicated that helper activity in the T cell population from low responder mice was not due to F(1) cells. Also, the level of contamination was not sufficient to quantitatively account for the help. In examining the genetic restriction of these tolerized T cells, we found that T cells from tolerized low responder B10.BR or C57BL/10 mice helped F(1) or high responder B10.D2 B cells and APC but not syngeneic B10.BR or C57BL/10 B cells and APC, which were immunized with Mb-coupled fowl gamma globulin instead of Mb to prime low responder B cells with Mb. On the other hand, high responder B 10.D2 tolerized T cells helped syngeneic B 10.D2 B cells but not allogeneic low responder B10.BR B cells. These data indicated that clones of helper T cells specific for Mb exist in low responder mice, and these are not phenotypically different from those in high responder mice, in that both help high responder and F(1) but not low responder B cells and APC. These data are discussed in terms of the mechanism for Ir gene control, and the mechanism of T cell repertoire development- whether intra- or extrathymically-in neonatally tolerized mice.     

CELLULAR DIFFERENTIATION OF THE IMMUNE SYSTEM OF MICE : VI. STRAIN DIFFERENCES IN CLASS DIFFERENTIATION AND OTHER PROPERTIES OF MARROW CELLS

Marrow cells and 5 x 10⁷ thymocytes of unprimed (C57BL/6 x DBA/2)F₁, (C57BL/10 x WB)F₁ and (C3H x C57BL)F₁ donor mice were mixed in vitro and transplanted into X-irradiated syngeneic hosts. Upon injection of sheep erythrocytes, splenic plaque-forming cells (PFC) secreting IgM (direct PFC or IgG (indirect PFC) hemolytic antibody were enumerated at the time of peak responses. By grading the numbers of marrow cells, inocula were found that contained few immunocompetent cells reaching the recipient spleens, interacting with thymocytes or other accessory cells (or both), and generating PFC. The frequency of responses in BDF₁ mice conformed to Poisson statistics, indicating that immunocompetent marrow cells participated in a single-hit interaction limiting PFC responses. The marrow cells assayed were not restricted for the antibody class (IgM versus IgG) to be secreted by mature PFC. Unrestricted marrow cells could have been either the precursors of PFC or accessory cells. Different results were obtained in BWF₁ and C3BF₁ mice. The frequency of responses in relation to the number of marrow cells grafted did not follow Poisson statistics, and the limiting cells were restricted for antibody class. Presumably, immunocompetent cells of these strains were more heterogeneous than those of BDF₁ mice and participated in a multiplicity of cell-to-cell interactions. The strain differences reflected inherent properties of marrow cells and not influences of the environment in which PFC were produced. The results confirmed for bone marrow the heterogeneity of immunocompetent cells reported by others for spleen, and suggested that genetic factors such as "immune response" genes regulate cellular differentiation also for functions other than those related to antibody specificity.     

The antibody response to specific immune complexes is under genetic control and correlates with the expression of a recurrent idiotype

The primary antigen-specific antibody response of various strains of mice to TEPC-15/PnC immune complexes has been examined. We found that both BALB/c and C3H mice were good responders to the PnC antigen; however, C3H mice were low responders, whereas BALB/c mice were high responders to the TEPC-15/PnC complexes. Using congenic strains on the C3H and BALB/c background, we have shown that the response to the complexes is not restricted by gene products of the H-2 complex or by the Igh (allotype) locus. However, responsiveness may be controlled by genes linked to the Igh locus, since we have shown that strains that are Ighj, Ighd, and Ighf are low responders, whereas strains that are Igha, Ighb, and Ighe are high responders to the immune complex. Moreover, responsiveness correlates with the expression of the T15 Id as measured using the anti-T15 monoclonal antibody, AB1-2. Thus, strains such as BALB/c, BALB.B, BALB.K, and CB-20, which express high levels of T15 (AB1-2) Id in their PFC response to PnC are relatively high responders to TEPC-15/PnC complexes, whereas C3H, C3H.SW, and C3H-OH, which express low levels of the T15 (AB1-2) Id, are low responders to the complexes. Finally, we found that BALB/c mice are high responders to complexes formed with T15+ antibodies, whereas they are low responders to complexes formed using T15- antibodies. The results suggest that the antigen-specific response to these immune complexes is Id-restricted.     

Innate immune response in Th1- and Th2-dominant mouse strains

C57BL/6 and BALB/c mice are prototypical Th1- and Th2-type mouse strains, respectively. In the present study, we attempted to characterize the innate immune response of macrophages from these mouse strains. Macrophages from C57BL/6 mice produced higher levels of tumor necrosis factor-alpha (TNF-alpha) and interleukin (IL)-12 than those from BALB/c mice after stimulation with macrophage-activating lipopeptide-2 (MALP-2, a synthetic TLR-2 ligand) or lipopolysaccharide (LPS, a TLR-4 ligand). The augmented IL-12 production by C57BL/6 macrophages increased interferon-gamma and, in contrast, decreased IL-13 production by CD4+ T cells. On stimulation with MALP-2 or LPS, C57BL/6 macrophages produced lysosomal enzyme and nitric oxide, effector molecules for bacterial killing, whereas BALB/c macrophages did not. Bactericidal activity of BALB/c macrophages was impaired relative to C57BL/6 macrophages when cells were infected with live bacteria in vitro. In a murine model of septic peritonitis induced by cecal ligation and puncture (CLP), BALB/c mice failed to facilitate bacterial clearance relative to C57BL/6 mice despite an augmented peritoneal leukocyte infiltration that was associated with increased peritoneal levels of cytokines/chemokines. BALB/c mice exhibited increased plasma and hepatic levels of cytokines/chemokines, resulting in an exaggerated systemic inflammation as determined by acute-phase proteins. Finally, BALB/c mice were vulnerable to CLP-induced lethality relative to C57BL/6 mice. Altogether, innate immune response of macrophages is different between these mouse strains, which may affect the development of Th1 and Th2 adaptive immunity in these strains. Reduced systemic inflammatory response in C57BL/6 mice that may result from an eminent local response appears to be beneficial during sepsis.