Allogeneic MHC antigen requirements for lupus-like autoantibody production and nephritis in murine graft-vs-host disease

A graft-vs-host (GVH) reaction of parental T cells in allogeneic F1 mice can lead to an autoimmune disease resembling human SLE. We analyzed the contribution of MHC genes to the development of IgG antinuclear antibody production and immune complex glomerulonephritis in MHC-congenic F1 recipients. DBA/2 T cells elicited IgG antibodies to histone, ssDNA, and dsDNA in all histoincompatible F1 recipients that were studied. The anti-DNA antibody responses were quantitatively similar among the F1 combinations and displayed comparable IgG2a subclass and cationic charge characteristics. In contrast, severe renal disease was manifested only in F1 mice that expressed H-2b encoded class II gene products. Disease susceptibility was associated with a decrease in circulating anti-DNA antibodies and a characteristic localization of immune complexes in the glomeruli. The data suggest that the production of potentially pathogenic IgG anti-nuclear antibodies is not sufficient for the development of renal disease in GVH-induced lupus. Thus, another event separate from autoantibody production is MHC dependent and appears to be critical for the formation and/or deposition of pathologic immune complexes.     

Failure of bone marrow cells to reconstitute T cell immunity in graft-vs-host mice

A chronic GVH reaction (detected by T cell immune deficiency) was induced in unirradiated, adult (C57BL/10 X B10.A)F1 mice by injecting them i.v. with 3 X 10(7) B10.A parental spleen cells. Thirty-four days later, attempts were made to reconstitute the GVH immune-deficient mice by whole-body irradiation and repopulation with bone marrow cells from normal syngeneic F1 mice. The reconstituted mice were tested for CTL responses 147 and 272 days after repopulation with normal F1 bone marrow. These GVH/chimera mice remained immunoincompetent for at least 272 days for CTL responses to hapten-self and H-2 allogeneic antigens.     

Interleukin 2 receptor dysfunction in mice undergoing a graft-vs-host reaction

Mice of the (C57BL/10 X B10.A)F1 combination were given a single i.v. inoculation of 3 to 4 X 10(7) B10.A spleen cells, which induces a graft-vs-host (GVH)-associated immune deficiency in F1 mice. Between 1 and 4 wk later, spleen cells from the F1 mice were tested for the expression of IL 2 receptors by flow microfluorometry, using the 7D4 rat monoclonal antibody directed against an epitope murine IL 2 receptor. A reduction in intensity of spleen cell staining with 7D4 was detected as early as 8 days after parental cell inoculation, and no IL 2 receptors were detected by 28 days after initiation of GVH. Furthermore, the loss of IL 2 receptors was correlated with abrogation of proliferative responses to concanavalin A and lipopolysaccharide, of IL 2 production, and of cytotoxic T lymphocyte responses. These observations may be relevant for our understanding of GVH reactions, of immune disorders associated with GVH, and possibly of primary and acquired immunodeficiencies in general.     

Immunosuppression of normal lymphoid cells by serum from mice undergoing chronic graft-vs-host disease.

Spleen cells from F1 mice undergoing chronic graft-vs-host (GVH) reaction, induced by injection of parental cells, were shown to be immunosuppressed since their in vitro responses to the mitogens concanavalin A (Con A) and bacterial lipopolysaccharide (LPS) were substantially lower than control animals. Serum, from mice undergoing GVH, when cultured in vitro with normal spleen cells was immunosuppressive. The proliferation response to Con A and allogeneic cells of normal syngeneic, allogeneic, and parental spleen cells was 90% suppressed when serum from mice undergoing chronic GVH was added in comparison to the addition of serum from untreated F1 mice. Similarly, the in vitro antibody response to a T-dependent antigen was impaired; however, the antibody response to a T-independent antigen was not impaired. These results indicate that T cell functions are more sensitive than are B cell functions to immunosuppressive factors in the serum of mice undergoing GVH.     

Specific partial depletion of graft-vs-host activity by incubation and centrifugation of mouse spleen cells on allogeneic spleen cell monolayers.

Spleen cells (from BALB/c mice immunized with the C57BL/6 lymphoma EL4, or from non-immune BALB/c) were incubated on monolayers of [C57BL/6 times BALB/cF1 (B6CF1) spleen cells on polylysine-coated polystyrene Petri plate, for 1/2 hr or for 1 hr at 37 degrees C followed by centrifugation of the monolayers for 5 min at 70 times G to 110 times G at 34 to 37 degrees C. Control monolayers were BALB/c spleen cells. As measured by the Simonsen spleen weight assay in neonatal mice, graft-vs-host (GVH) activity was partially depleted in cell populations nonadherent to B6CF1 monolayers. Residual GVH activity of these nonadherent cells was about half that of cells incubated on the control syngeneic monolayers (the mean of eight experiments was 49% +/- 11% S.D.). Two or three consecutive cycles of incubation and centrifugation did not significantly diminish the residual GVH activity, suggesting that spleen cells with GVH activity are heterogeneous with respect to binding to allogeneic target cells under the above conditions. Cell populations nonadherent to third-part [A times AL]F1 monolayers retained full activity, and cell populations partially depleted of GVH activity in B6CF1 neonates had full activity in third-party [BALB/c times AL]F1 neonates.     

Change of incidence of antinuclear antibodies in serum of NOD mouse with aging

Extractable nuclear antigens (ENA) were prepared from liver of C57BL/6J mouse and analyzed by SDS PAGE Western-immunoblotting techniques. Some protein components of the ENA, with molecular weights of 94 K, 65 K, 32 K, and 26 K, reacted with antinuclear antibodies in the sera of NOD mice. Incidence of antinuclear antibodies in the sera of NOD mice with aging were measured by ELISA method using the ENA as antigen. The antinuclear antibodies were not detected in young NOD mice (10 weeks old). However, the incidence increased with aging and reached 100% in the female NOD mice of 40 weeks. In the male NOD mice, the incidence of antinuclear antibodies was delayed and low in comparison with that in female.     

Role of L3T4+ and Lyt-2+ donor cells in graft-versus-host immune deficiency induced across a class I, class II, or whole H-2 difference

The i.v. injection of parental T cells into F1 hybrid mice can result in a graft-vs-host (GVH)-induced immune deficiency that is Ag nonspecific and of long duration. The effect of the GVH reaction (GVHR) on the host's immune system depends on the class of F1 MHC Ag recognized by the donor cells. To determine the role of different subsets of donor-derived T cells in the induction of GVHR, donor spleen cells were negatively selected by anti-T cell mAb and C, and the cells were injected into F1 mice that differed from the donor by both class I and II MHC Ag or by class I or class II MHC only. The induction of GVHR across class I + II differences was found to require both L3T4+ and Lyt-2+ parental cells. Induction of GVHR across a class II difference required only L3T4+ parental T cells in the combination tested [B6-into-(B6 x bm12)F1]. In contrast, B6 Lyt-2+ cells were sufficient to induce GVHR across a class I difference in (B6 x bm1)F1 recipients. In addition, a direct correlation was observed between the cell types required for GVH induction and the parental T cell phenotypes detected in the spleens of the GVH mice. The number of parental cells detected in the unirradiated F1 hosts was dependent upon the H-2 differences involved in the GVHR. Induction of a class I + class II GVHR resulted in abrogation of both TNP-self and allogeneic CTL responses. In contrast, induction of a class II GVHR resulted in only a selective loss of TNP-self but not of allogeneic CTL function. Unexpectedly, the induction of a class I GVHR also resulted in the selective loss of the TNP-self CTL response. Thus, these class I and class II examples of GVH both result in the selective abrogation of L3T4+ Th cell function. The data are discussed in terms of respective roles of killer cells and/or suppressor cells in the induction of host immune deficiency by a GVHR, and of the selective deficiency in host Th cell function induced by different classes of GVHR.     

Cellular immunity and blocking serum activity in chimeric mice

Mice (9 CBA × T6, 6 T6, and 7 CBA) were irradiated and repopulated with foreign (BALB/c) bone marrow. Lymph node cells from 16 of 18 repopulated mice not showing signs of graft versus host disease (GVH), were cytotoxic to host type fibroblasts but not to BALB/c fibroblasts, and sera from the same mice could block lymphocyte mediated cytotoxicity. No blocking was seen with sera from three mice which had signs of GVH. LNC from the latter three mice were cytotoxic to recipient fibroblasts.It is suggested that the blocking effect detected in vitro may protect against GVH in vivo, but the relative importance of the blocking phenomenon as compared to other mechanisms is not yet settled.     

Chronic progressive polyarthritis and other symptoms of collagen vascular disease induced by graft-vs-host reaction

The induction of a GVHR in (BALB/c X A)F1 mice by i.v. injection of 80 to 120 X 10(6) BALB/c spleen cells leads to the development of chronic progressive polyarthritis, which shares several of the articular and extra-articular manifestations of human rheumatoid arthritis. The development of these lesions was found to be mediated by donor T cells and to require the presence of histoincompatibility between donor and host. The arthritis, which was mainly confined to the interphalangeal joints of the forefeet and hindfeet, was histologically characterized by periarticular and synovial lymphoid infiltrations, as well as synovial proliferation and pannus formation. Prominent juxta-articular lesions included 1) perivascular infiltrates, 2) peritendinitis, 3) myositis, and 4) inflammatory nodules. In addition, the GVH F1 mice showed pathologic symptoms reminiscent of other collagen vascular diseases, including the following: 1) a Sj?gren-like salivary gland lesion, 2) lesions resembling sclerosing cholangitis, 3) scleroderma-like skin lesion, and 4) immune-complex glomerulonephritis. In most of the GVH F1 mice, these pathologic changes were accompanied by lymphoid stimulation. The spectrum of symptoms induced has many similarities to that found in mixed connective tissue disease.     

Murine graft vs host disease. A model for study of mechanisms that generate autoantibodies to ribonucleoproteins

We established chronic graft vs host disease in (BALB/c x A/J) F1 mice with the injection of lymphoid cells from the parental A/J strain. These animals developed glomerulonephritis, forefoot edema, alopecia, splenomegaly, and lymphadenopathy to various degrees, and all developed antinuclear antibodies. To determine whether these antibodies were directed against the small nuclear ribonucleoprotein (snRNP) particles that are characteristic targets for autoimmune responses in human rheumatic diseases, sera were studied in the 32P immunoprecipitation and immunoblotting assays. Among 20 mice, antibodies to snRNP developed in 10. These antibodies usually reached maximal levels about 4 wk after induction of graft vs host disease and generally fell thereafter. However, two mice developed antibodies to snRNP between the 10th and 20th wk of follow-up. Sera from six mice strongly recognized the U1 snRNP and an additional serum strongly bound both the U1 and U3 particles. Several sera contained lower levels of antibodies specific for the U3 and possibly pre-U2 snRNP particles. In immunoblots, sera that immunoprecipitated the U1 snRNP bound epitopes located on its 70,000 Da, A, B'/B, and/or C polypeptides. Sera that immunoprecipitated the U3 snRNP recognized a 34,000-Da polypeptide. These polypeptides are known to bear the autoantigenic epitopes that are recognized by human sera containing anti-U1 RNP and anti-U3 RNP autoantibodies. We conclude that chronic graft vs host disease in mice provides a model for the study of the autoimmune responses that characterize human diseases such as mixed connective tissue disease, scleroderma, and SLE.     

Role of cytotoxic T lymphocytes in the prevention of lupus-like disease occurring in a murine model of graft-vs-host disease

The inoculation of B6D2F1 mice with T lymphocytes from the C57BL/6 parental strain induces an "immunosuppressive" graft-vs-host reaction (B6 GVH), whereas inoculation of T cells from the other, DBA/2 parental strain induces an "immunostimulatory" GVH reaction and a lupus-like disease (DBA GVH). The present study compares cytotoxic T lymphocyte (CTL) function in the spleens of these GVH mice as well as differences in the donor inoculum that could account for these different types of GVH. We observed that the B6 GVH induces an immunodeficiency that encompasses CTL precursors (and possibly T helper cells) and results in suppressor cells that abrogate responses to both trinitrophenyl (TNP)-modified self and third party alloantigens. In contrast, the DBA GVH induces only a T helper cell immunodeficiency and results in suppressor cells selective for class II restricted L3T4+ T helper cells. Chimeric T cells were detected in both types of GVH. In the B6 GVH both L3T4+ and Lyt-2+ donor cells were observed, although Lyt-2+ cells predominated. In the DBA GVH, donor T cells were almost exclusively of the L3T4+ phenotype. The lack of appreciable donor Lyt-2+ cells in the DBA GVH can be explained by a defect in the DBA donor inoculum manifested by a naturally occurring two-fold reduction in Lyt-2+ cell numbers as well as a nine-fold reduction in CTL precursors with anti-F1 specificity. T cells in the DBA inoculum, therefore, are predominantly L3T4+. A similar defect induced in B6 donor cells by anti-Lyt2 antibody and complement not only converted the suppressive GVH to a stimulatory GVH, as measured by anti-DNA antibodies, but also resulted in a T cell immune deficiency characteristic of the DBA GVH, i.e., a selective loss of the TNP-self CTL response. Thus the presence or absence of adequate numbers of functioning Lyt-2+ cells in the donor inoculum is correlated with the development of either a suppressive or stimulatory GVH, respectively. That donor Lyt-2+ cells mediate a suppressive GVH through cytolytic mechanisms is evidenced by greater than 70% reduction in B6 GVH spleen cell numbers and readily demonstrable anti-F1 CTL activity by these spleen cells despite an inability to generate anti-allogeneic or anti-TNP self CTL activity even in the presence of added T helper factors.(ABSTRACT TRUNCATED AT 400 WORDS)     

SPECIFIC positive and negative selection of rat lymphocytes reactive to strong histocompatibility antigens: activation with alloantigens in vitro and in vivo.

This study compares the functional properties of rat thoracic duct lymphocytes (TDL) after stimulation with strong alloantigens of the major histocompatibility complex (MHC) either in vitro in preparative mixed lymphocyte interactions (MLI) or in vivo in systemic graft-vs-host (GVH) reactions. Comparisons were made of PHA responses and reactivity to the specific priming haplotypes or to third party haplotypes in analytical MLI and in GVH reactions either before or after the activated populations were "parked" in syngenetic T cell-deprived (B) rats. These comparisons can be summarized as follows: 1) TDL populations primed in bulk MLI cultures (MLI-TDL) slowed some evidence of specific positive selection when tested immediately; MLI responses to specific alloantigens were both relatively large and accelerated in tempo, whereas responses to third party alloantigens were diminished but also accelerated in tempo. Specific GVH responses were more marked than in third party recipients but they were also decreased relative to normal, and displayed an abberant dose/response slope. MLI-TDL populations tested after they had been stored in syngeneic B rats showed clear evidence of stable-specific positive selection; specific MLI and GVH responses were enriched relative to third party responses and also in comparison to normal, unselected TDL populations. This finding indicates that GVH and MLI reactivity are probably both functional capacities of the same lymphocyte subpopulation since positive selection by one function (MLI) also enriched for a second (GVH). 2) Parental strain TDL activated in vivo in the systemic GVH reaction in irradiated F1 animals and recovered from the thoracic duct 3 to 4 days later (late GVH-TDL) consisted mainly of blast cells, however, in contrast to MLI-TDL these populations showed no evidence of positive selection when tested before or after parking in B rats. MLI responses to specific alloantigens were minimal, and greatly reduced in magnitude compared to normal. GVH responses to specific haplotypes could be detected, but these were not enriched compared to normal, despite the content in the late GVH-TDL populations of a significant proportion of blast cells presumably activated by host alloantigens. 3) Early collections (less than 40 hr) of parental strain GVH-TDL collected from F1 recipients contained no blast cells and showed impressive degrees of negative selection; they were markedly depleted of both GVH and MLI activity to specific alloantigens but displayed normal reactivity to third party alloantigens. Moreover, specific negative selection was persistent in these populations parked for several weeks in B rats, and indication that a specific subpopulation of reactive cells had been physically eliminated. 4) PHA responses of both MLI- and GVH-activated TDL populations tested either before or after parking in B rats were approximately normal on a per T cell basis...     

In vivo allogeneic effects: shift in the isotype profile of primary TI-2 responses in mice undergoing graft-vs-host reaction

We showed previously that primary responses to T-dependent (TD) and T-independent type 2 (TI-2) antigens were differentially affected by allogeneic effects induced in vivo during a graft-vs-host reaction (GVH). TD responses were greater than or equal to 80% suppressed, whereas the TI-2 responses were greatly enhanced, particularly the IgG component, which normally is very low. We have analyzed the IgG subclass distribution in primary responses of normal and GVH F1 mice in order to determine whether the strong T cell signals that occur during GVH reactions also induce shifts in the isotype profile. The effect of GVH on responses to TI-2 antigens was of particular interest because they are usually dominated by IgM and IgG3 classes in normal mice. We found a threefold to 10-fold increase in the PFC numbers of all four IgG subclasses in the response to TI-2 antigens, with an apparent shift from the usual IgG3 dominance to IgG1 in GVH mice. This IgG1 dominance was not found in serum antibodies where IgG3, IgG1, and IgG2b were equally expressed, although total IgG was increased greater than 20-fold. No isotype shift was found in either the TNP-KLH response, which was greater than or equal to 75% suppressed (IgG1 dominance was retained), or in the TI-1 response to TNP-Ba. The latter response was reduced (25 to 50%) in GVH mice and continued to be dominated by IgG2b/2a and IgG3. Unlike the unique isotype patterns found in primary responses, TNP-KLH primed mice challenged with TD, TI-1, or TI-2 antigens gave memory responses with identical isotype profiles that were dominated by IgG1 PFC. The role of T cells in B cell differentiation and isotype expression is discussed.     

Allosuppressor- and allohelper-T cells in acute and chronic graft-vs-host disease. IV. Activation of donor allosuppressor cells is confined to acute GVHD

Groups of nonirradiated BDF1 mice were injected with unseparated spleen cells from B10, B10.D2, or DBA/2 donors. The diverse clinical and pathologic symptoms that developed during the course of the ensuing graft-vs-host reaction (GVHR) were related to the functional subsets of donor-T cells activated in the host. The activation of F1-specific donor T suppressor (TS) cells was confined to those GVH F1 mice that developed acute GVH disease (GVHD) (donor B10 or B10.D2). Moreover, activation in these GVH F1 mice of the Lyt-1-2+ donor TS cells sharply preceded the onset of and coincided with (week 2 to 6) the suppressive pathologic symptoms characteristic of acute GVHD, such as pancytopenia and suppression of splenic IgG production. The activation of these alloreactive TS effector cells was briefly preceded by the activation of F1-specific Lyt-1+-2- donor T helper (TH) cells and stimulation of the host's lymphoid tissue. Thus, in acute GVHD, a sequential alloactivation first of donor TH and then of TS cells was found. Those F1 mice that recovered from acute GVHD and developed stimulatory pathologic symptoms showed a concomitant loss of donor TS cell activity. An initial activation of F1-specific Lyt-1 +2- donor TH cells was also found in that parent----F1 combination (donor DBA/2), which failed to develop acute GVHD. Significantly in that combination, the alloactivation of donor TH cells was not followed by activation of significant numbers of donor TS cells. Instead, the DBA/2-injected BDF1 mice directly developed a persistent increase in splenic Ig formation and lupus-like GVHD.     

Hematopoietic factors in graft-versus-host reaction

Graft-versus-host (GVH) reaction has a curious unsolved area in the immunopathogenesis and pathophysiology of the immunohematopoietic system, and GVH disease remains one of the major obstacles in clinical allogeneic bone marrow transplantation. T lymphocytes and T lymphocyte subpopulations are now recognized to be initiators of this GVH reaction and disease. Also, T lymphocytes are known to be accessory cells in the regulation of hematopoiesis, and produce a variety of lymphokines relevant to hematopoiesis. Admittedly, remarkable hematopoietic changes can be found in GVH reaction, but the cellular mechanisms underlying these changes are so complex they have yet to be fully elucidated. In fact, elevated serum levels of myeloid and erythroid colony-stimulating activities were found in mice suffering from GVH disease in which marked granulopoiesis and suppression of erythropoietic differentiation were seen. In addition, each granulocyte/macrophage colony-stimulating factor (GM-CSF) or burst-promoting activity (BPA) could be detected in sera from patients with GVH disease following allogeneic bone marrow transplantation. There seems to be at least two mechanisms involved in the control of hematopoiesis with either humoral or local environmental factor, probably via the T lymphocytes or T lymphocyte subpopulations activated by alloantigens or autologous non-T cells.     

Graft-vs-host reaction limited to a class II MHC difference results in a selective deficiency in L3T4+ but not in Lyt-2+ T helper cell function

Hybrid mice of the (B6 X bm12)F1 combination were inoculated i.v. with parental B6 spleen cells to induce a class II graft-vs-host disease (GVH). Such mice failed to generate in vitro cytotoxic T lymphocyte (CTL) responses that were dependent upon L3T4+ T helper cell (Th) function (e.g., anti-B6-TNP) but were capable of generating in vitro CTL responses that could be mediated by Lyt-2+ Th cells (anti-allo class I). When Th function was assayed directly by interleukin 2 (IL 2) secretion, class II GVH animals were found to be deficient in L3T4+ but not Lyt-2+ IL 2-secreting Th cells. This selective deficiency in L3T4+ Th function correlates with a selective decrease in class II GVH mice of host-derived derived L3T4+ T cells. In addition, it was found that the spleens of class II GVH mice contained cells capable of selectively suppressing L3T4+ Th function. In contrast, mice in which a class I + II GVH occurred were depleted of both L3T4+ and Lyt-2+ Th function as assessed by IL 2 production. The findings that class II GVH selectively depletes L3T4+ T cells and T cell functions are discussed with respect to the immune function of distinct T cell subsets in normal and diseased states.     

Orderly pattern of development of the autoantibody response in (New Zealand White x BXSB)F1 lupus mice: characterization of target antigens and antigen spreading by two-dimensional gel electrophoresis and mass spectrometry

Immunoblots of a two-dimensional PAGE-separated HL-60 cell proteomic map and mass spectrometry were combined to characterize proteins targeted by autoantibodies produced by male (New Zealand White x BXSB)F(1) (WB) mice that develop lupus and anti-phospholipid syndrome. Analysis of sera sequentially obtained from seven individual mice at different ages showed that six proteins, vimentin, heat shock protein 60, UV excision-repair protein RAD23, alpha-enolase, heterogeneous nuclear ribonucleoprotein L, and nucleophosmin, were the targets of the B cell autoimmune response, and that autoantibodies to them were synthesized sequentially in an orderly pattern that recurred in all the male WB mice analyzed: anti-vimentin first and anti-nucleophosmin last, with anti-RAD23 and anti-heat shock protein 60, then anti-alpha-enolase and anti-heterogeneous nuclear ribonucleoprotein L Abs occuring concomitantly. Anti-vimentin reactivity always appeared before anti-cardiolipin and anti-DNA Abs, suggesting that vimentin is the immunogen initiating the autoimmune process. The pattern of HL-60 proteins recognized by female WB sera differed from that of male sera, indicating that the Y chromosome-linked autoimmune acceleration gene is not an accelerator but a strong modifier of the autoimmune response. Thus, 1) combining two-dimensional PAGE and mass spectrometry constitutes a powerful tool to identify the set of Ags bound by autoantibodies present in a single serum and the whole autoantibody pattern of an autoimmune disease; 2) the diversification of the autoimmune response in male WB mice occurs in a predetermined pattern consistent with Ag spreading, and thus provides a useful model to further our understanding of the development of the autoantibody response in lupus.     

The elaboration of leukotactic mediators during the interaction between parental-type lymphocytes and F1 hybrid cells.

Mixed leukocyte cultures consisting of white blood cells from (Lewis times BN) F1 hybrids and Lewis parents produced monocyte chemotactic factor. Elaboration of this material preceded incorporation of 3H-thymidine. Local graft vs host (GVH) reactions were induced by subcapsular injection of parental thoracic duct cells into F1 hybrids. Homogenates from these kidneys, but not from kidneys injected with syngeneic thoracic duct cells, contained monocyte chemotactic factor. Little or no neutrophil chemotactic factor was present. Ultracentrifugal analysis of the monocyte chemotactic factor indicated a distribution similar to that found previously in culture fluids of lymphoid cells stimulated by soluble antigens. Differential counts of inflammatory cells extracted in suspension form from kidneys undergoing a GVH reaction indicated the majority of cells to be lymphocytic in type, but with a significant proportion of monocytes. Virtually no neutrophils were present. These findings indicate that a monocyte chemotactic factor is produced by cultures of parental leukocytes stimulated by semiallogeneic cells and that a similar factor appears in GVH reactions in the rat kidney. This chemotactic factor may be relevant to the character of the cellular exudates.     

Anti-Ro autoantibody with cross-reactive binding to the heavy chain of immunoglobulin G.

Autoantibodies directed at the intracellular Ro ribonucleoprotein complex are found in the serum of patients with systemic lupus erythematosus (SLE) and related autoimmune diseases. The antigenic stimulus for the induction of these autoantibodies is unknown, although we have previously demonstrated that the Ro protein and immunoglobulin G (IgG) share immunologic determinants bound by anti-Ro antibodies. The present study further defines the fine specificity of this cross-reactive binding. Using both patient autoanti-Ro antibodies and antigen-induced rabbit anti-Ro serum, the binding specificity for IgG was located to the heavy chains of IgG outside the Fc domain. F(ab')2 fragments of IgG were observed to inhibit specific Ro binding by either human or antigen-induced rabbit sera, while Fc fragments of IgG failed to inhibit Ro binding. Anti-Ro sera were found to bind the heavy chains of IgG in immunoblots, and the antibodies eluted from these heavy chains were capable of immunoprecipitating the Ro particle from human cell extracts. Not all patient sera with anti-Ro antibodies possessed IgG binding antibodies. Studies of cyanogen bromide digestion fragments of IgG implicate the hinge region of IgG as the region cross-reactive with the Ro protein. The nature of this cross-reactivity may be important in understanding the induction and/or perpetuation of the anti-Ro response in patients with autoimmune disease.     

Reactivation of allergic encephalomyelitis by means of allogeneic confrontation

Lewis rats recovered from experimental allergic encephalomyelitis (EAE) are resistant to active reinduction of disease. (DA X Lewis)F1 hybrids behave in an identical fashion. The induction of a graft versus host (GVH) reaction in EAE convalescent (DA X Lewis)F1 rats, by injection of normal parental (Lewis) lymphocytes, precipitates a second episode of EAE in a proportion of rats. This secondary episode of EAE can be induced by injection of parental cells either systemically (intravenously) or locally (subcutaneously in the foot). A host versus graft (HVG) reaction does not reactivate EAE in the convalescent host. The observed effect is probably due to reactivation of EAE effector cells following the extensive nonspecific proliferation of host lymphoid cells which is a feature of GVH reactivity.