Influence of protein restriction on immune functions in NZB mice.

The influence of a low protein (6%) diet on the immunologic function of NZB mice was investigated. The low protein intake was associated with decreased weight gain in both male and female NZB mice. The mice fed the low protein diet did not develop splenomegaly, which generally occurs by 7 to 10 months of age in NZB mice fed a normal amount of protein. Further, 7- to 10-month-old NZB mice fed the low protein(6%) diet, maintained: 1) more vigorous antibody production to sheep red blood cells; 2) greater capacity to produce graft-vs-host reactions, and 3) more vigorous cell-mediated "killer" cell immunity after immunization against DBA/2 mastocytoma cells than did NZB mice on a normal (22%) protein diet. The decrease of PHA and Con A response which normally occurs with aging in NZB mice was abrogated to some degree by protein restriction. However, response to LPS, which also declines with age in NZB mice, did not appear to be influenced by diet.     

NZB mice exhibit a primary T cell defect in fetal thymic organ culture

Defects in T cell development have been suggested to be a factor in the development of systemic autoimmunity in NZB mice. However, the suggestion of a primary T cell defect has often been by extrapolation, and few direct observations of T cell precursors in NZB mice have been performed. Moreover, the capacity of NZB bone marrow T cell precursors to colonize the thymus and the ability of the NZB thymic microenvironment to support T lymphopoiesis have not been analyzed. To address this important issue, we employed the fetal thymic organ culture system to examine NZB T cell development. Our data demonstrated that NZB bone marrow cells were less efficient at colonizing fetal thymic lobes than those of control BALB/c or C57BL/6 mice. In addition, NZB bone marrow cells did not differentiate into mature T cells as efficiently as bone marrow cells from BALB/c or C57BL/6 mice. Further analysis revealed that this defect resulted from an intrinsic deficiency in the NZB Lin-Sca-1+c-kit+ bone marrow stem cell pool to differentiate into T cells in fetal thymic organ culture. Taken together, the data document heretofore unappreciated deficiencies in T cell development that may contribute to the development of the autoimmune phenotype in NZB mice.     

Culture and characterization of thymic epithelium from autoimmune NZB and NZB/W mice

Autoimmune NZB and NZB/W mice display early abnormalities in thymus histology, T cell development, and mature T cell function. Abnormalities in the subcapsular/medullary thymic epithelium (TE) can also be inferred from the early disappearance of thymulin from NZB. It has also been reported that NZB thymic epithelial cells do not grow in culture conditions that support the growth of these cells from other strains of mice. In order to study the contribution of TE to the abnormal T cell development and function in NZB and NZB/W mice, we have devised a culture system which supports the growth of TE cells from these mice. The method involves the use of culture vessels coated with extracellular matrix produced by a rat thymic epithelial cell line. TEA3A1, and selective low-calcium, low-serum medium. In addition TEA3A1 cells have been used as an antigen to generate monoclonal antibodies specific for subcapsular/medullary TE. These antibodies, as well as others already available, have been used to show that the culture conditions described here select for cells displaying subcapsular/medullary TE markers, whereas markers for cortical TE and macrophages are absent.     

Selective improvement of thymus and some T cell dysfunctions in NZB mice by in utero thymulin treatment

NZB mice were treated during gestation with thymulin, a thymus-secreted, zinc-associated nonapeptide. Control pregnant NZB mice received either zinc alone or saline alone. Offspring from all three groups of NZB mothers, and age-matched DBA/2 mice, were tested for the following immunologic parameters: thymulin serum levels at 2 and 5 wk of age; splenic anti-sheep red blood cell (anti-SRBC) plaque-forming cell (PFC) numbers after immunization at birth or at 2 wk of age; anti-human gamma-globulin (anti-HGG) antibody titers after immunization at 2 wk of age, with or without prior tolerance induction at birth with deaggregated HGG; spontaneous IgM serum levels at 2 and 5 wk of age; spontaneous splenic anti-trinitrophenyl (anti-TNP) PFC numbers at 2 wk of age. As compared with DBA/2 mice, young NZB mice exhibited low circulating thymulin titers, high antibody responses to SRBC and to HGG, resistance to tolerance induction by deaggregated HGG, increased spontaneous IgM serum levels, and increased spontaneous anti-TNP PFC numbers. However, marked reductions in anti-SRBC and anti-HGG antibody production, both thymus-dependent responses, were observed in the young NZB offspring of thymulin-treated mothers as compared with NZB controls born from zinc- or saline-treated mothers. A delay in the postnatal decrease of serum thymulin levels was also noted in the offspring of thymulin-treated mothers. Interestingly, these effects of in utero thymulin treatment tended to become more pronounced with advancing age during the postnatal period. Conversely, IgM serum levels, spontaneous anti-TNP PFC and sensitivity to tolerance induction were not affected by thymulin treatment during fetal life. Taken together, the data suggest that in utero exposure to pharmacologic concentrations of thymulin induces a persistent and selective improvement of some thymus and T cell dysfunctions but has no effect on intrinsic B cell abnormalities of NZB mice.     

Studies of congenitally immunologic mutant New Zealand mice. II. Absence of T cell progenitor populations and B cell defects of congenitally athymic (nude) New Zealand Black (NZB) mice.

Congenitally athymic (nude) mice on an NZB, NZW, and BALB/c background were produced by repetitive selective backcrossing. F'12 generation nude mice of these three strains were compared to their littermate nu/+ controls with respect to survival, histology, blood counts, splenic surface markers, response to mitogens, spontaneous plaque-forming cells, and appearance of naturally occurring thymocytotoxic antibodies (NTA). Under specific pathogen-free conditions, NZB nude mice survive less than 3 weeks, dying of a runting-like disease with infection by local normally noninvasive organisms. A contributing factor to his premature death is the relative absence of T cell progenitor populations in the NZB nude vs NZW nude or BALB/c nude groups. Furthermore, NZB nude mice have a significantly earlier appearance of NTA than nu/+ littermates and likewise appear to have heightened spontaneous polyclonal B cell responses against the haptens dansyl, nitroiodophenyl, trinitrophenyl,2,4 dinitrophenyl, and sulfonate. It is suggested that NZB mice have several critical immunologic defects, including abnormalities of thymic epithelial cells, T cell differentiation pathways, and chronically polyclonal activated B cell populations. These defects interact to produce the clinical expression of autoimmunity.     

Defective isotype-specific regulation of IgA anti-erythrocyte autoantibody-forming cells in NZB mice

B cell hyperactivity characterizes many autoimmune diseases. In NZB mice this is manifested by a variety of immunologic aberrations, including increased B cell proliferation and hyper IgM and IgA secretion in vitro. Recent studies have shown that IgA secretion can be suppressed or enhanced in an isotype-specific manner by a soluble factor(s), called IgA-binding factor (IgABF), produced by IgA FcR-bearing T cells. We now show that T cells from young NZB mice, cultured with high concentrations of IgA, produce an IgABF that has aberrant biologic activity when compared to IgABF produced from IgA FcR+ T cells of BALB/c mice. Although BALB/c IgABF normally suppresses proliferation and secretion by IgA-producing B cells, neither proliferation nor IgA secretion from normal murine IgA-B cells is suppressed by NZB IgABF. In fact, IgA secretion is significantly enhanced by NZB IgABF. We also present the first evidence of IgA anti-mouse erythrocyte (anti-MRBC) autoantibody-forming cells present in the spleens of NZB mice. Whereas BALB/c IgABF suppresses the in vitro generation of IgA anti-MRBC autoantibody-forming cells by NZB spleen cells, NZB IgABF enhances this response. Of particular interest is the development of IgA anti-MRBC autoantibody-forming cells in cultures of spleen cells from nonautoimmune BALB/c mice in the presence of NZB IgABF. These studies suggest that isotype-specific T cells factors might play an important role in the development of autoantibody-forming cells.     

Transferred B cells from autoimmune NZB/N mice fail to activate T suppressor cells

T-cell-mediated suppression of the antibody response of autoimmune NZB/N mice to Type III pneumococcal polysaccharide (SSS-III) can readily be induced in situ by priming with a subimmunogenic dose of SSS-III; however, the transfer of either "young" (8 weeks old) or "old" (42 weeks old) SSS-III-primed B cells, which activates suppressor T cells in normal BALB/cByJ mice, fails to induce suppression of the antibody response in recipient NZB/N mice, regardless of the number of cells transferred or the time interval between transfer and immunization. Transfer of 51Cr-labeled B cells demonstrated that syngeneic primed B cells home to the spleens of NZB/N mice in somewhat lower numbers than in BALB/cByJ mice, although the differences observed may not be sufficient to explain the complete absence of activation of suppressor T cells. These findings suggest that B cells from autoimmune NZB/N mice are unable to activate T suppressor cells upon transfer; this disorder in a normal regulatory mechanism may be important in the pathogenesis of disease.     

B-B cell interactions in the spontaneous activation of B cells in autoimmune NZB mice.

We analyzed the mechanism of spontaneous B cell activation in lupus mice by using anticlass-II antibody in vitro. The in vitro culture of B cells from old NZB mice markedly produced Ig without any stimulation, while B cells from NZW mice did not. The addition of anticlass-II antibody (anti-Iad antibody) to the culture inhibited Ig production of NZB B cells in a concentration-dependent manner. On the other hand, the addition of anticlass-I antibody (anti-H-2Dd antibody) and anticlass-II antibody with different specificity (anti-Iak) gave no effect on the Ig production of NZB B cells. When mitomycin C-treated B cells were added to in vitro culture of responder B cells as a stimulator, Ig production of responder B cells was enhanced in a concentration-dependent manner. However, the enhancing effect of the stimulator B cells was abrogated by the pretreatment with anticlass-II antibody. The stimulator B-cell activity to NZB B cells was marked in NZB B cells, moderate in NZB/W F1 B cells, and weak in NZW B cells. Furthermore, the stimulator B-cell activity with regard to NZB B cells was marked in old female NZB B cells, moderate in old male NZB B cells, and weak in young NZB B cells. The expression of class II antigens on the surface of old female NZB B cells was significantly higher than that of old male NZB and young NZB B cells. These results suggest that in lupus mice the spontaneous B-cell activation is induced by an abnormal B-B cell interaction mediated by class II antigens.     

Effects of calorie restriction on immunologic functions and development of autoimmune disease in NZB mice.

Chronic energy (calorie) intake restriction (CEIR) prolonged life, inhibited autoimmune disease, and influenced immunologic and hematologic parameters in NZB mice. Abnormalities in numbers and proportions of T and B cells populations were corrected. Deficient responses to phytomitogens, mixed lymphocyte reactions, formation of plaque-forming cells to sheep red blood cells in vitro, production of cytotoxic T lymphocytes after in vitro stimulation, and interleukin 2 production were also corrected. CEIR prevented the extreme splenomegaly that normally occurs with age in NZB mice. This influence was associated with reduction of a greatly expanded non-T, non-B lymphoid cell population. Calorie restriction also prevented in NZB mice the rapid decrease in total numbers of colony-forming B cells in bone marrow that is also characteristic of mice of this strain. The influences of CEIR on immune parameters and hematopoiesis were generally less marked in non-autoimmune-prone DBA/2 mice than in autoimmune-prone NZB mice. CEIR has been shown to produce profound influences on several strains of autoimmune-prone mice (NZB x NZW)F1, MRL/lpr, BXSB, and NZB herein). In each of these strains, the pathogenesis and manifestations of autoimmune disease are dissimilar. Therefore, it seems likely that calorie restriction acts on an as yet elusive mechanism that operates to foster development of the diseases associated with aging common to each of these autoimmune strains as well as autoimmune-resistant mice and rats. Further investigation of the molecular and cellular bases of the benefits of CEIR seems urgent.     

Genetic studies in NZB mice. II. Hyperdiploidy in the spleen of NZB mice and their hybrids.

The presence of hyperdiploidy was studied in New Zealand black (NZB) mice and the progeny of NZB X DBA/2 crosses and backcrosses. Hyperdiploidy was observed in the spleens of a majority of NZB mice but not in DBA/2 mice at 1 year of age. In crosses of NZB with the DBA/2 strain, hyperploidy was observed only in backcrosses to NZB. Hyperdiploidy appeared to be determined by a recessivley inherited trait and was not related to the presence of other immunological abnormalities, including splenomegaly, hypergammaglobulinemia, and spontaneous antibodies cytotoxic for T cells and reactive with single-stranded DNA. Abnormal cells were not present in Concanavalin A-stimulated 48-h spleen cultures. There was no difference in the in vitro sister chromatid exchange rate between the autoimmune NZB strain and the non-autoimmune DBA/2 strain. Identification of NZB chromosomes by banding analysis showed that chromosomes 15 and 17 were frequently present in more than two copies in hyperdiploid spleen cells. NZB chromsomes also had reduced C-banding in an autosomal pair. These studies indicate that chromosomal abnormalities which occur in NZB mice may be useful as genetic and cytogenetic markers.     

Detection of autologous mixed lymphocyte reaction responding cells and their precursor frequency in NZB mice

The autologous mixed lymphocyte reaction (AMLR) can be detected in older NZB mice after treatment of the responding cell population with monoclonal anti-I-A^d and complement and supplementation of the culture medium with T-cell growth factor (TCGF) from young animals. The addition of TCGF to cultures containing responding cells alone that had not been pretreated with anti-I-A plus complement resulted in high levels of background proliferation. This is indicative of a high number of preexisting I-A-positive, activated, TCGF-responsive T cells in these mice. These activated cells could also be removed by treatment with anti-I-A antibody and panning on anti-mouse Ig plates, or by BUdR and light killing of those cells proliferating in the presence of TCGF or purified IL-2. Prior treatment of the responding cells with anti-Lyt 2 and complement did not effect the AMLR. An NZB AMLR responding cell line was established using these methods. This line retained haplotype specificity in a proliferation assay. Limiting dilution analysis of the precursor frequency of AMLR responding cells in the nonautoimmune C58 and BALB/C strains in culture medium with TCGF gave a frequency of between 1 in 35,000 and 1 in 88,000. In young, AMLR-positive, NZB mice, supplementation with TCGF yielded precursor frequencies within the normal range. In older NZB mice, the addition of TCGF resulted in increased background proliferation of preactivated, IA⁺ T cells. After removal of these cells with anti-I-A plus complement, AMLR responding cells were found at normal frequency levels when stimulated in the presence of TCGF. In the oldest animals tested (greater than 18–20 weeks), normal precursor frequencies could not be demonstrated even after this treatment, representing a true decline in the AMLR responding cell number. AMLR deficiency in NZB mice appears therefore to be the result of the combined effects of decreased lymphokine production, excessive T-cell activation, and finally decreased numbers of AMLR responding cells.     

Studies of congenitally immunologically mutant New Zealand mice. IX. Age-related microenvironmental effects on autoantibody production in NZB and NZB.Xid mice studied by transplantation

The mechanism of polyclonal expansion of B cells and subsequent autoantibody production in New Zealand mice remains a critical question. We have been studying the requirements for autoantibody production both in NZB mice as well as NZB mice congenic with the Xid gene of CBA/N mice. In this study, we have attempted to alter the immunologic phenotype of NZB.Xid mice by transfer of cells from young and old NZB mice. There was little difficulty in restoring normal levels of serum IgM, IgG3, splenic Lyb-5 cells, and response to DNP-Ficoll in young NZB.Xid mice that were injected with young NZB bone marrow cells. Although such animals had an almost immediate change in their immune profile to values characteristic of NZB mice, they required, much like unmanipulated NZB mice, a latency period of an additional 6 mo before autoantibodies were detected. In contrast, adult NZB.Xid mice, who likewise developed an immune profile similar to NZB after transfer of bone marrow cells from young NZB mice, began to express autoantibodies immediately without any latency period. NZB.Xid mice who were recipients of adult NZB bone marrow cells did not show sustained autoantibody production, reflecting the limited state of B cell precursors in adult NZB mice. Thus, the age of both donor cells and the age of recipient mice are critical factors for determining the latency period and the age at which autoantibodies will appear. Similarly we attempted to alter the production of autoantibodies in NZB mice that were irradiated and injected with bone marrow cells from NZB.Xid animals. NZB mice had a major amelioration of disease when they received cell transfers from young NZB.Xid mice. This amelioration, which included the acquisition of the immune profile of NZB.Xid animals, was not seen in adult NZB mice that were recipient of young NZB cells. We suggest that although Lyb-5 cells may be the effective mechanism for autoantibody production, there are other interacting influences that may selectively turn on or turn off autoantibodies and that are required and are responsible for the latency period.     

Treatment of NZB/NZW mice with total lymphoid irradiation: long-lasting suppression of disease without generalized immune suppression

We used total lymphoid irradiation (TLI; total dose = 3400 rad) to treat the lupus-like renal disease of 6-mo-old female NZB/NZW mice. Similar to our past studies, this treatment resulted in a marked prolongation of survival, decrease in proteinuria, and decrease in serum anti-DNA antibodies compared with untreated littermate controls. Although there was no evidence of disease recurrence in TLI-treated mice until after 12 mo of age, the in vitro proliferative response to phytohemagglutinin by NZB/NZW spleen cells recovered within 6 wk such that responses were greater than control NZB/NZW animals. A similar recovery and overshoot after TLI were evident in the primary antibody response to the T cell-dependent antigen sheep red blood cells (SRBC). Both the total and IgG anti-SRBC antibody responses after TLI were greater than those of untreated NZB/NZW controls, and were comparable with those of untreated non-autoimmune mice. Despite this increased response to mitogens and antigens after TLI, we noted a decrease in spontaneous splenic IgG-secreting cells and a decrease in IgG but not IgM antinuclear antibody production. Nonspecific suppressor cells of the mixed leukocyte response were detectable in the spleens of NZB/NZW mice early after TLI. However, the disappearance of suppressor cells was not associated with recrudescence of disease activity. Furthermore, transfer of large numbers of spleen cells from TLI-treated NZB/NZW mice did not result in disease suppression in untreated age-matched recipients. In summary, treatment of NZB/NZW mice with TLI results in a prolonged remission in autoimmune disease, which is achieved in the absence of generalized immunosuppression.     

The regulatory role of NZB T lymphocytes in the production of anti-DNA antibodies in vitro

Murine lupus is characterized by the production of numerous autoantibodies and immune complex glomerulonephritis. Anti-DNA antibodies are the hallmark of this disorder and may be associated pathogenetically with the glomerulonephritis. The cellular mechanisms underlying the regulation of the production of anti-DNA antibodies may prove to be the fundamental abnormalities responsible for the lupus syndrome seen in these mice. By using a system of spontaneous anti-DNA antibody production in vitro, we have determined that such production is characteristic of autoimmune NZB and MRL-lpr/lpr mice but not of the nonautoimmune control strains. Additional examination of the cellular mechanisms involved in the regulation of this response in NZB mice revealed: 1) this response is markedly T cell dependent, 2) NZB T cells are essential for maximal production of this autoantibody, and 3) NZB T cells actively interfere with normal immune regulatory mechanisms that lead to the production of anti-DNA antibodies spontaneously in vitro by nonautoimmune syngeneic B lymphocytes. Although these studies of anti-DNA antibody production in vitro disagree with previous work by others they successfully reproduce the results obtained earlier in experiments performed in vivo.     

Thymic epithelial genotype influences the production of recombinant leukemogenic retroviruses in mice

By using T1 oligonucleotide fingerprinting and mapping techniques, we analyzed the genomic structure of retroviruses produced by thymocytes and splenocytes of reciprocal bone marrow-and thymus-grafted chimeras. We found that the genetic factor(s) derived from NZB mice that suppresses the development of thymic leukemia in (AKR X NZB)F1 mice also prevents the formation of recombinant leukemogenic viruses and the expression of preleukemic changes in the (AKR X NZB)F1 thymocytes. The NZB mouse gene or genes appeared to exert this suppressive effect by acting on the thymic reticuloepithelial cells and not on the thymic lymphocytes of (AKR X NZB)F1 hybrids. Prospective studies with thymic epithelial grafts from young mice showed that the AKR thymic epithelium could mediate the formation and expression of leukemogenic recombinant viruses and preleukemic changes in thymocytes that lead to the development of thymic leukemia, whereas the (AKR X NZB)F1 thymic epithelium was deficient in this regard. Our results also confirmed a previous observation that during in vivo generation of recombinant leukemogenic viruses, the acquisition of polytropic virus-related sequences in the 3' portion of the p15E gene and the U3 region and in the 5' part of the gp70 gene can occur independently.     

Immunologic abnormality in NZB/NZW F1 mice. Thymus-independent occurrence of B cell abnormality and requirement for T cells in the development of autoimmune disease, as evidenced by an analysis of the athymic nude individuals

Both NZB nu/+ and NZW nu/+ mice were microbially clean by cesarean section. The (NZB x NZW)F1 hybrid (NZB/W) nu/nu mice and nu/+ littermates were then generated by mating of NZB nu/+ with NZW nu/+mice under specific pathogen-free conditions. The female NZB/W F1 nu/nu mice did not develop autoimmune kidney disease, whereas all of nu/+ female littermates mice exhibited proteinuria and died of renal failure with a 50% survival time of 35 wk. Namely, nude mice had no signs of proteinuria up to the time of their death caused by other diseases rather than glomerulonephritis, and their mean survival time was greater than 45 wk. Nude mice had also no anti-ssDNA antibody in their serum. However, splenic B cells of NZB/W nude mice exhibited hyper-responsiveness to both LPS and B151-TRF2, a T cell-derived polyclonal B cell-stimulation factor, and produced large numbers of Ig-secreting cells and anti-TNP plaque-forming cells as well as anti-ssDNA antibody comparable to the nu/+ littermate mice. Interestingly, thymus-engrafted NZB/W nude mice developed autoimmune disease exemplified by the induction of anti-ssDNA antibody and proteinuria at approximately the same time as their nu/+ littermates. These results indicate that the B cell hyper-responsiveness found in NZB/W mice is apparently determined by the T cell-independent process, and T cells are obligatorily required for the development of autoimmune disease in NZB/W mice.     

Properties of fractionated spleen cells from NZB/W mice.

The unit gravity sedimentation technique was used to separate spleen cells from sevveral strains of mice. Settling patterns (plot of cell number against settling rate) were similar for BALB/c, DBA/2, C3H/He, and NZB/W mice of different ages. In particular, no subpopulation was found by this technique to be missing from the spleens of old NZB/W mice.A number of functional studies performed with the separated cells proved more informative than the settling patterns themselves. Fractions of cells which sedimented at a rate of between about 6 mm/hr and 10 mm/hr were enriched in responsiveness to PHA, Con A, and allogeneic cells. These fractions obtained from old NZB/W mice lacked such activities. However, the active fractions from young NZB/W spleens, which were enriched in θ-bearing cells, could restore the responsiveness of old NZB/W mice to primary immunization with sheep erythrocytes. These studies indicate that functional separation of spleen cells from NZB/W mice is possible and that activities lacking in whole spleens from old NZB/W mice are also lacking in the separate fractions. The ability to restore helper T cell function in old NZB/W mice with active fractions from young NZB/W mice has implications for further study and treatment of their autoimmune disease.     

Impaired development of T lymphoid precursors from pluripotent hematopoietic stem cells in New Zealand Black mice.

Bone marrow cells from autoimmune-prone New Zealand Black (NZB) mice are less efficient at colonizing fetal thymic lobes than cells from normal strains. This study demonstrates that the reduced capacity of NZB bone marrow cells to repopulate the thymus does not result from their inability to migrate to or enter the thymus. Rather, the T lymphopoietic defect of NZB mice is due to an impaired ability of pluripotent hematopoietic stem cells (PHSCs) to generate more committed lymphoid progeny, which could include common lymphoid precursors and/or other T cell-committed progenitors. Although PHSCs from NZB mice were not as efficient at thymic repopulation as comparable numbers of PHSCs from control strains, the ability of common lymphoid precursors from NZB mice to repopulate the thymus was not defective. Similarly, more differentiated NZB T cell precursors included in the intrathymic pool of CD4(-)CD8(-) cells also exhibited normal T lymphopoietic potential. Taken together, the results identify an unappreciated defect in NZB mice and provide further evidence that generation of lymphoid progeny from the PHSCs is a regulated event.     

In vitro production of anti-histone antibodies by spleen cells from young autoantibody negative NZB/NZW mice

Anti-histone antibodies (AHA) are spontaneously produced in NZB/NZW mice as part of their autoimmune disease. IgM AHA are usually not detected until after 4 mo of age, and older female mice switch to the production of IgG AHA. We studied the in vitro production of AHA by spleen cells from young (less than or equal to 12-wk-old) NZB/NZW mice. Despite the absence of elevated serum AHA activity, spleen cells from these mice demonstrated marked spontaneous autoantibody production in culture. In kinetic studies, little in vitro production was detectable after 1 day of culture, and maximal accumulation occurred on day 5. Elevated AHA production was apparent by cells from 2-wk-old NZB/NZW mice, and an age-dependent increase in autoantibody production was also noted. Only AHA of the IgM class were detected in cultures of young spleen cells. The in vitro production of IgM AHA in culture was T cell dependent, depletion of T cells resulting in a 70 to 90% reduction in production, which was corrected by the readdition of T cells. In cultures where both IgM AHA and total IgM secretion were measured, a much greater T cell dependence for AHA production was apparent. The requirement for T cells could also be partially replaced by factors present in concanavalin A supernatant. AHA secretion was induced by lipopolysaccharide by using cells from both NZB/NZW and non-autoimmune mice. Although production was greater with NZB/NZW cells, the difference was much less than that for spontaneous production. Thus, AHA-secreting cells that are dependent on in vitro T cell help are present in young NZB/NZW mice. These studies may help define the mechanisms responsible for selective autoantibody secretion in lupus-like disease.     

Total lymphoid irradiation reduces IgG autoantibody production and enhances specific antibody responses in NZB/NZW F1 mice

Thymus-independent primary antibody responses were studied in young and old (9 months) untreated and TLI-treated NZB/NZW and BALB/c mice. Untreated old NZB/NZW mice had a low primary response to Brucella abortus (BA) as compared to that of young NZB/NZW and BALB/c mice. However, TLI treatment resulted in a 130-fold increase in the IgG anti-BA primary antibody response at day 21 postimmunization, achieving similar levels to those of young NZB/NZW or nonautoimmune BALB/c mice. Anti-TNP responses to trinitrophenylated BA or Ficoll were masked by high background levels of anti-TNP antibodies. Despite the increase in the anti-BA response, spontaneous immunoglobulin secretion and autoantibody levels were markedly decreased after TLI in old NZB/NZW mice.