B cell depletion delays collagen-induced arthritis in mice: arthritis induction requires synergy between humoral and cell-mediated immunity

Rheumatoid arthritis is a systemic autoimmune disease. B cells are likely to play a critical role in arthritis pathogenesis, although it is unclear whether they are necessary for disease induction, autoantibody production, or disease progression. To assess the role of B cells in inflammatory arthritis, B cells were depleted using mouse anti-mouse CD20 mAbs in a mouse model of collagen-induced arthritis. CD20 mAbs effectively depleted mature B cells from adult DBA-1 mice. When B cells were depleted using CD20 mAbs before collagen immunization, there was a delay in disease onset and autoantibody production, with significantly diminished severity of arthritis both clinically and histologically. B cell depletion further delayed disease onset if initiated before, as well as after, collagen immunization. However, in both cases, the eventual reappearance of peripheral B cells triggered autoantibody production and the subsequent development of arthritis in collagen-sensitized mice. By contrast, B cell depletion after collagen immunizations did not have a significant effect on arthritis progression or severity. Thus, disease symptoms were only induced when peripheral B cells and their autoantibody products were present in collagen-immunized mice, documenting a critical role for B cells during the elicitation phase of collagen-induced arthritis. These studies suggest that B cell depletion strategies will be most effective when initiated early in the development of inflammatory arthritis, with sustained B cell depletion required to inhibit the production of isotype-switched pathogenic Abs and the evolution of joint inflammation and destruction.     

Interaction between cytokines and 8-mercaptoguanosine in humoral immunity: synergy with interferon

In previous studies it has been demonstrated that a T cell-like differentiation signal is transmitted by C8-substituted guanine ribonucleosides such as 8-mercaptoguanosine (8MGuo) to antigen-stimulated B cells. A large subset of potentially reactive B cells remains unresponsive to antigen even in the presence of signals provided by these nucleosides except when this signal is preceded by a soluble activity present in mixed lymphocyte culture supernatants. Studies with purified preparations of interleukin (IL)-1, IL-2, IL-3, granulocyte-macrophage colony stimulating factor, B cell stimulatory factor 1 (IL-4), and B cell growth factor II (IL-5) indicated that none of these activities is capable of synergizing with 8MGuo to augment B cell responsiveness to antigen. Therefore, supernatants from a number of cloned cell lines were examined for activity that could synergize with 8MGuo, in order to determine the cellular source of this activity. Soluble products secreted by cloned 24/G1 T cells act synergistically with 8MGuo to evoke enhanced antibody responses to specific antigen in populations of purified B cells. Because concanavalin (Con) A-activated 24/G1 cells produce large quantities of interferon-gamma (IFN-gamma), the possibility that interferons might mediate synergy with 8MGuo was investigated. Purified murine IFN-gamma is unable to interact synergistically with 8MGuo; moreover, treatment of active 24/G1 supernatants with monoclonal anti-IFN-gamma antibodies or at pH 2 fails to abrogate their ability to synergize. In contrast to IFN-gamma, when B cells were supplemented with either IFN-alpha or IFN-beta, antigen-dependent synergy with 8MGuo was observed. However, abrogation of IFN-alpha and IFN-beta activity with specific antibodies fails to interfere with synergy between 8MGuo and mixed lymphocyte culture or Con A supernatants. Therefore, it appears that although IFN-alpha and IFN-beta are not responsible for the synergizing activity present in activated T cell supernatants, they nonetheless represent a previously unrecognized source of synergizing activity.     

Type II collagen-induced arthritis in mice. III. Suppression of arthritis by using monoclonal and polyclonal anti-Ia antisera

Pretreatment of mice genetically susceptible to type II collagen-induced arthritis (CIA) with monoclonal or polyclonal antisera specific for I region gene products (Ia antigens) suppressed or delayed the onset of CIA, whereas pretreatment with anti-Ia to an irrelevant haplotype was without effect. The humoral response to type II collagen was transiently depressed 14 days after immunization but antibody levels did not differ significantly after 28 days. The peak delayed-type hypersensitivity to type II collagen was unaffected by anti-Ia treatment. Monoclonal antibody of one anti-Ia specificity enhanced both the antibody response and the arthritis incidence in one mouse strain.     

Type II collagen-induced murine arthritis: induction of arthritis depends on antigen-presenting cell function as well as susceptibility of host to an anticollagen immune response.

Two sets of ((resistant x susceptible) F1----parent) and (parent----F1) chimeric mice were prepared. In the chimeric combinations involving BALB/c and DBA/1 mice, all (F1----F1) chimeras developed arthritis as well as potent anticollagen responses after immunization with collagen, whereas all (F1----BALB/c) and (BALB/c----F1) chimeras induced neither arthritis nor immune responses. This type of F1 T cells could be activated with APC from DBA/1 but not from BALB/c mice. Thus, the failure of the [F1 in equilibrium with BALB/c] chimeras to mount anticollagen responses was due to a defect at the APC level. Another arthritis-resistant strain, C57BL/6, exhibited adequate APC function, but reduced T cell responsiveness, representing an intermediate responder. In the chimeric combinations involving C57BL/6 and DBA/1 mice, (F1----F1) and (C57BL/6----C57BL/6) chimeras developed very high and very low incidence of arthritis, respectively. (C57BL/6----F1) chimeras developed an appreciable incidence of arthritis under conditions in which this group of chimeras generated intermediate levels of anticollagen responses. In contrast, (F1----C57BL/6) chimeras developed low incidence of disease despite induction of strong responses. Moreover, cells from collagen-immunized (F1----C57BL/6) chimeras, when transferred into T cell-depleted B cell mice of F1 or C57BL/6 strain, produced comparable immune responses in both groups but induced much more severe arthritis in F1 than in C57BL/6 recipients. These results indicate that: i) two types of arthritis-resistant strains can be identified, each of which has anticollagen APC defect as a low responder and reduced T cell responsiveness as an intermediate responder and ii) a discrepancy between the degree of anticollagen responses and clinical arthritis is attributed to the differential susceptibility to anticollagen immune responses.     

Immune response to chemically modified flagellin. IV. Further studies on the relationship between humoral and cell-mediated immunity

Acetoacetylation converts flagellin from an antigen which preferentially induces humoral antibodies to an antigen which exclusively provokes cell-mediated immunity and, under certain circumstances, induces antibody tolerance. Studies reported in this paper revealed that the acetoacetylated flagellins expressed similar immunological properties in flagellin primed rats as in normal rats. Thus, on the one hand, acetoacetylation destroyed the capacity of flagellin to trigger a secondary antibody response, but on the other hand, the acetoacetyl-flagellins very effectively induced delayed-type hypersensitivity reactions in flagellin primed animals. It was concluded from these results that humoral and cell-mediated immunity may be opposing immunological processes in both unprimed and primed animals.Acetoacetylated flagellin induced antibody tolerance in both strain W (low responder) and J (high responder) Wistar rats. Maximum tolerance was induced 12 hr after injection of antigen, but in strain J animals the tolerance had disappeared by 48 hr, whereas in strain W rats tolerance persisted for >28 days. The potential to recover from tolerance in strain J rats appeared to coincide with the level of delayed hypersensitivity at the time of challenge. However, this delayed hypersensitivity disappeared when breaking of tolerance occurred. These results suggest that the T cells which participate in delayed hypersensitivity reactions may also act as “helper” cells in antibody responses. On the other hand, it was found that priming for a secondary antibody response by flagellin appeared to coincide with development of primary antibodies rather than with induction of delayed-type hypersensitivity. The relative importance of specific T and B cells in these phenomena is discussed.     

T cell regulation of collagen-induced arthritis in mice. I. Isolation of Type II collagen-reactive T cell hybridomas with specific cytotoxic function

After immunization with native type II collagen (CII), susceptible strains of mice (H-2q) develop a polyarthritis that mimics rheumatoid arthritis. Although the underlying mechanisms are still undefined, T cells and particularly CD4+ lymphocytes seem to play a crucial role in the initiation of collagen-induced arthritis. To investigate whether CD8+ cells may participate in the pathogenesis of the disease, we have generated lines and clones of cytotoxic T cell hybridomas reactive to CII by fusion of lymph node and spleen cells from bovine native CII-primed C3H.Q (H-2q) mice and the AKR-derived thymoma cell line BW 5147. Clones were selected for their ability to lyse syngeneic macrophages pulsed with bovine native CII in an Ag-dependent manner. The two hybrid clones that were characterized, exhibited cell surface phenotypes of cytotoxic cells and reacted with CII purified from various species. However, each of them recognized different determinants on the CII molecule. P3G8 clone was specific for an epitope shared by CII and type XI collagen, whereas P2D9 clone reacted with CII and type IX collagen. Both hybridomas recognized CII-pulsed targets in association with H-2Kq molecules. These data indicate that the two CII-specific cytotoxic clones recognize different epitopes that are shared by other articular collagens and will allow us to test their influence on the development of arthritis in vivo.     

Differential effects of concanavalin A and phytohemagglutinin on murine immunity. Suppression and enhancement of cell-mediated immunity.

To assess the effects of the selective T-cell mitogens concanavalin A (Con A) and phytohemagglutinin P (PHA) on cell-mediated immunity (CMI), the mitogens were injected before, with, or after intravenous (iv) challenge of mice with Listeria monocytogenes. Mitogenic treatment differentially influenced the CMI response to Listeria. Con A enhanced listericidal activity when given before or with Listeria challenge, but Con A suppressed the CMI response when given after infection with Listeria. In contrast, PHA enhanced listericidal activity at all intervals. Since Con A, but not PHA, affected the growth of Listeria in the spleens of mice 24 and 48 hr after infection, Con A was shown to have an immediate effect on the development of listericidal activity and PHA was shown to have a delayed effect. In addition, Con A induction of immediate nonspecific listericidal activity was short-lived, while PHA induced a longer-lasting effect on resistance to Listeria. The mitogen-induced effects in the CMI response to Listeria were shown to be dependent upon the activities of activated T cells. The enhancement and suppression of listericidal activity appears to result from the activation of different T-cell subpopulations, known to be stimulated preferentially by Con A or PHA.     

Differential effects of concanavalin A and phytohemagglutinin on murine immunity. Suppression and enhancement of humoral immunity.

The abilities of concanavalin A (Con A) and phytohemagglutinin P (PHA) to selectively induce different T-cell activities affecting humoral immunity were evaluated. The mitogens were intravenously injected before, with, or after injection of sheep red blood cells (SRBC) into mice, and the 3 to 6-day plaque-forming cell (PFC) responses were assessed. Mitogenic treatment differentially influenced the resultant in vivo PFC responses to SRBC. The in vivo suppressive effects induced by Con A were shown to be temporary; only the Day 4 PFC response was inhibited. Con A given 3 hr before, with, or after the antigenic challenge enhanced the PFC response. In contrast, PHA given at all intervals inhibited both the 4- and 5-day PFC response. Neither mitogen appeared to affect the kinetics of the in vivo PFC response to SRBC. Both mitogens enhanced in vivo DNA synthesis by the splenic cells, and Con A appeared biphasic in its stimulation. Con A-induced effects on the humoral immune response were short-lived and transient, while PHA induced a longer-lasting effect on humoral immunity.     

Induction of cell-mediated immunity to chemically modified antigens in guinea pigs. II. The interaction between lipid-conjugated antigens, macrophages, and T lymphocytes.

Protein antigens covalently conjugated with lipid groups (dodecanoic acid) have previously been shown to stimulate strong delayed-type hypersensitivity (DTH) without the aid of adjuvants. The present experiments show that lipid-conjugated bovine serum albumin (L-BSA) is taken up in vitro by macrophages (Mpsi) 25- to 50-fold more than unconjugated BSA or aminidated BSA, neither of which induces DTH. Macrophages that take up 125I-labeled L-BSA in vitro stimulate DTH even more efficiently, when injected into syngeneic guinea pigs, than does soluble L-BSA. Tracer studies on the fate of radiolabeled BSA and L-BSA showed that much more L-BSA than BSA was retained by draining lymph nodes. Autoradiography demonstrated that 125I-L-BSA is rapidly taken up by Mpsi in the medullary sinuses of the lymph nodes. Some of this antigen is then transported into the paracortex, a region in which T lymphocytes predominate. The capacity of lipophilic antigens to stimulate cell-mediated immune responses may be caused by their increased uptake by Mpsi, resulting in more efficient presentation to immunocompetent T lymphocytes. The anatomical site of this Mpsi-T cell interaction may be within the sinusoids or paracortex of the draining lymph nodes.     

Discrimination of suppressor T cells of humoral and cell-mediated immunity by anti-Ly and anti-Ia sera.

Evidence is presented which demonstrates that the T lymphocytes which suppress humoral and cell-mediated immunity in CBA/H mice differ in the cell surface structures they express. The suppressor T cells of delayed-type hypersensitivity are Ly-1⁺, Ly-2^? and Ia^?, whereas the suppressor T cells of antibody formation are Ly-1^?, Ly-2⁺ and Ia⁺.     

Paradoxical effects of adenovirus-mediated blockade of TNF activity in murine collagen-induced arthritis.

Collagen-induced arthritis (CIA) is an experimental model of arthritis widely used to dissect the pathogenesis of human rheumatoid arthritis and to identify potential therapeutic targets. Among these, TNF-alpha has been recognized to play an important role. Here we investigate the feasibility and therapeutic efficacy of prolonged blockade of TNF-alpha activity through the adenovirus-mediated gene delivery of a dimeric chimeric human p55 TNFR-IgG fusion protein and compare it to protein therapy in established CIA. A single i.v. administration of the replication-deficient adenovirus yielded microgram serum levels of the chimeric fusion protein and ameliorated CIA for 10 days. Subsequently, benefit was lost and a rebound to greater inflammatory activity was observed despite the continual presence of bioactive TNFR fusion protein. A similar trend was also observed in mice injected directly with comparable amounts of a human TNFR-IgG fusion protein, whereas the administration of a control adenovirus-encoding beta-galactosidase or of a control human IgG1 protein did not significantly affect the disease course. The mechanisms of the rebound of CIA were investigated, and augmented Ab response to collagen type II and TNFR were identified as potential causes. Our results confirm the feasibility of adenovirus-mediated gene delivery of cytokine inhibitors in animal models of autoimmune diseases for investigational purposes and highlight the importance of prolonged studies. Further investigations are needed to optimize ways of exploiting the potential of adenoviral gene therapy in RA.     

Vascular endothelial growth factor expression and regulation of murine collagen-induced arthritis

We have examined the expression and function of the angiogenic factor, vascular endothelial growth factor (VEGF) during the evolution of type II collagen-induced arthritis (CIA). Biologically active VEGF was expressed along a time course that paralleled the expression of two specific VEGF receptors, Flk-1 and Flt-1, and the progression of joint disease. Moreover, levels of VEGF expression correlated with the degree of neovascularization, as defined by vWF levels, and arthritis severity. Macrophage- and fibroblast-like cells, which infiltrated inflamed sites and were then activated by other inflammatory mediators, are probably important sources of VEGF and may thus regulate angiogenesis during the development of CIA. Administration of anti-VEGF antiserum to CIA mice before the onset of arthritis delayed the onset, reduced the severity, and diminished the vWF content of arthritic joints. By contrast, administration of anti-VEGF antiserum after the onset of the disease had no effect on the progression or ultimate severity of the arthritis. These data suggest that VEGF plays a crucial role during an early stage of arthritis development, affecting both neovascularization and the progression of experimentally induced synovitis.