Immunological tolerance in bone marrow-derived lymphocytes. 3. Tolerance induction in primed B cells by hapten conjugates of unrelated immunogenic or "nonimmunogenic" carriers

Mechanisms of action of immune tolerance induction against factor VIII in patients with congenital haemophilia A and factor VIII inhibitors

In its most severe form, haemophilia A is a life-threatening haemorrhagic bleeding disorder that is caused by mutations in the factor VIII (FVIII) gene. About 25% of patients who receive replacement therapy with intravenous FVIII products develop neutralising antibodies (FVIII inhibitors) that inhibit the function of substituted FVIII. Long-term application of high or low doses of FVIII has evolved as an effective strategy for eradicating antibodies and inducing long-lasting immune tolerance. Despite clinical experience with the therapy, little is known about the immunological mechanisms that cause the down modulation of FVIII-specific immune responses or the induction of long-lasting immune tolerance against FVIII. This review summarises current knowledge of the immunological mechanisms that might be involved in the induction of immune tolerance against FVIII in patients with haemophilia A who have FVIII inhibitors. In addition to data from patients with haemophilia A, data from patients who have had organ transplants or have immune-related disorders, such as autoimmune diseases, are considered as well as data from animal models.

Reprogramming the immune system

The immune system is organized so as to react to pathogens without risking damage to self. Harnessing those processes that prevent self-reactivity will have enormous potential in clinical medicine. This review outlines the efforts of this laboratory over the last 25 years to exploit tolerance so as to reprogram the immune system for therapeutic purposes.

B Cell Tolerance to a Minor, But Not to a Major, Antigenic Surface of the Self Antigen, Cytochrome c

To study B cell tolerance to the mitochondrial protein cytochrome c (CYT), the B cell response to pigeon CYT (PCC) was examined in mice transgenic for PCC. PCC was coupled to OVA to provide T cell help, since PCC-specific T cells in PCC-transgenic mice are deleted in the thymus. The frequency of secondary B cells responding to the minor antigenic surface around residue 44 on PCC was decreased about 10-fold in native PCC-transgenic mice compared with that in control mice or in transgenic mice expressing an altered form of PCC that lacked the heme and had a different amino acid sequence at the N-terminus. A similar decrease has been observed in the frequency of B cells in normal mice recognizing the site around residue 44 on mouse CYT compared with the frequency of B cells recognizing the corresponding site on foreign CYT. There were no major decreases but apparently were compensatory increases in the frequencies of B cells recognizing other sites on PCC in the native PCC-transgenic mice compared with those in other mice. These results indicate that B cells in mice are only partially tolerant to self CYT. A possible basis for this partial tolerance relating to the fate of CYT in cell death is discussed. This may be the first example of the use of a transgenic system to study B cell tolerance to a homologous self Ag.

Induced specific immunological unresponsiveness & conditioned behavioral reflexes, in functional isomorphism-meditation and conditioned specific unresponsiveness

Detailed functional isomorphism had been observed (Freed, 1984) between induced (conditioned) immunogenicity and classical conditioned defensive reflexes, possibly as evolutionary adaptation against danger at micro and macro levels respectively. Similarly, functional isomorphism is postulated between conditioned specific tolerogenicity of the immunotolerance system and behavioral reflexes. Isomorphism requires that sensory signals elaborated with intrinsic (unconditioned) behavioral tolerogens as carriers do not subsequently combine classically with unconditioned aversive stimuli and evoke conditioned defensive responses. Unconditioned behavioral tolerogenic carriers were identified with behavioral (physiological) activities of Oriental meditation. Confirmation of conditioned behavioral tolerogenicity appeared in the unresponsiveness of Yogi mediators to sensory stimuli as reflected in unchanged alpha rhythms of their encephalograms. Conditioned behavioral specific unresponsiveness maintains the "quiet" of meditation and mediates the experience of Zen mediators, namely, sharpened, clearer perceptions and unresponsiveness to aversive components of current conditioned signals ordinarily reactivating residues of affect. Conditioned behavioral specific unresponsiveness has survival value.

Limiting dilution analyses for the quantification of cellular immune responses in bovine ostertagiasis

A sensitive limiting dilution analysis (LDA) was used to quantitate the local and systemic cellular immune response of cattle after immunization with keyhole limpet hemocyanin (KLH) and infection with Ostertagia ostertagi. The assay measures the proliferative response of bovine T-cells after in vitro stimulation with antigen. Interleukin 2 activity was supplied by supernates from mitogen-stimulated bovine peripheral blood lymphocytes (PBL) and accessory cell function was in the form of irradiated autologous PBL. The assay measures the response of a single cell and was most easily demonstrated in the lymph nodes draining the site of antigen inoculation. Comparison of cell frequencies and maximal responses generated in conventional proliferative assays showed several differences between the two assays. First, after antigen injection, the highest cell frequencies were seen in the draining lymph nodes within 3 days, and decreased by 10 days post-immunization. In contrast, in mass cultures maximal stimulation was not seen until 7-10 days after injection, but remained high up to 4 weeks after immunization. Second, at 17 days post-infection, a time of eruption of the parasite from the gastric glands, high frequencies of inducible cells were demonstrated by LDA in all lymphoid populations tested. In contrast, low levels of proliferation were seen in mass cultures. The reasons for these differences may include different sensitivities to suppression or more stringent requirements for specificity between the two assays. Finally, it was found that immunologically naive calves have relatively high frequencies of Ostertagia-specific cells in PBL, and that after infection these frequencies decrease. These results indicate either active suppression of the potential anti-Ostertagia response or an extra-vascularization of these cells to the site of infection.

Primed lymphoid cell tolerance. II. In vivo tolerization of highly tolerogen-sensitive hapten-primed, potentially IgG-producing B cells

The relative ease of tolerizing IgM-bearing versus IgG-bearing B cells was investigated. Previous work had shown that IgG-bearing trinitrophenyl (TNP)-specific B cells from mice primed and boosted with TNP-keyhole limpet hemocyanin (TNP-KLH) are highly susceptible to tolerization in vitro by TNP presented on an unrelated carrier. TNP-OVA was used as tolerogen, as it may represent a more general class of tolerogens than those which are nonmetabolizable or immunoglobulin containing. This study showed that highly primed B cells are tolerizable in vivo using TNP-OVA, with the IgG response to TNP-KLH easier to tolerize than the IgM response. To determine if the ease of tolerization of the IgG response in vivo was due to intrinsic differences in B-cell precursors of the IgM and IgG responses, tolerance was performed in vitro with B cells of defined surface isotypes. A T-independent antigen, TNP-endotoxin, was employed to minimize T-cell effects. At least 10 times as much TNP-OVA was required to tolerize B cells bearing the IgM surface isotype than those with the IgG surface isotype. Thus, the ease of inhibition of the IgG response as compared to the IgM response in vivo by preexposure to TNP-OVA may be at least partially explained by inherent differences in IgM and IgG B-cell precursors.

Inhibition of the passive cutaneous anaphylaxis reaction to Dactylis glomerata pollen allergens by a purified component of this pollen

By isoelectric focusing a protein fraction of pI 4.6 was isolated from a crude water-soluble extract of Dactylis glomerata pollen (SE). This fraction was neither immunogenic nor allergenic in BALB/c mice. In one week, this protein inhibited the mouse IgE-specific antibodies to the soluble extract as measured by PCA in rats and was therefore called Dactylis inhibitory protein (DIP). Two experimental approaches which lowered IgE anti-SE titer were undertaken. Pretreatment with DIP as well as injection of DIP after the last sensitizing injection with SE resulted in an inhibition of the circulating IgE antibody level to SE. For both experiments the regulation of the immune response touched only the IgE class, whereas the titers of anti-SE IgG, IgM, IgA antibodies were not modified. DIP treatment did not alter the IgE titers, measured by PCA, in the immune response to ovalbumin.

Suppressor T cell memory. II. The role of memory suppressor T cells in tolerance to human gamma globulin

The transient presence of suppressor T cell (Ts) activity in high-dose tolerance to human gamma globulin (HGG), and its (apparent) absence in low-dose tolerance, have been advanced as strong evidence against the concept that Ts play an important role in maintenance of immunological unresponsiveness. To analyze this question, CBA mice were exposed to high or low doses of deaggregated HGG (dHGG) and later challenged with HGG in immunogenic form (aHGG); their capacity to mount a primary or secondary suppressive response was assessed in an adoptive hapten-carrier system. Primary suppression reached a maximum 7 d after high-dose tolerance induction and gradually waned thereafter, being no longer detectable by day 30-35. Subsequent challenge of tolerant mice with aHGG, however, led to a rapid reactivation of suppression that bore the hallmarks of an anamnestic secondary response, and this effect was still demonstrable 135 d after tolerance induction. It was also shown that a single low dose of dHGG was capable of generating memory for suppression despite the absence of detectable primary suppression, indicating that the latter is not a prerequisite for induction of memory cells. The results were interpreted as indicating that tolerance, like immunity, is a manifestation of specific immunological memory. If tolerance to self-antigens is maintained by a similar mechanism, it would be expected that memory Ts could be induced during the early stages of fetal development. Mice were therefore exposed to tolerogen in utero by injection of their mothers with dHGG at day 7 of gestation, and were assessed at various times after birth for the capacity to exhibit primary or secondary suppression in adoptive transfer. Nonspecific suppression masked any specific effects during the first 5 wk of life. Antigen-specific, primary suppression was demonstrable subsequently until 10-12 wk of age, and if the animals were challenged with aHGG before transfer an anamnestic secondary suppressive response could be elicited up to 6 mo of age. These observations are consistent with the notion that memory Ts may play an important role in the maintenance of self-tolerance.

In vitro tolerance induction of primed, IgD-negative murine spleen cells

The above observations demonstrated induction of immunological tolerance in vitro in primed IgD-, IgG+ B cells. In these studies, addition of trinitrophenylated (TNP) turkey gammaglobulin (TGG) or TNP ovalbumin conjugates suppressed the secondary in vitro response in mice primed with TNP keyhole limpet hemocyanin (TNP-KLH). Suppression was not a reflection of a shift in kinetics of the antibody response, was not dependent on suppressor T cells, and could only be eliciate when conjugate was added within 4 h of addition of TNP-KLH moreover, preincubation of the primed spleen cells with TNP-TGG for 20 h at 37 degrees C, followed by extensive washing, was as effective in inhibiting the response to TNP-KLH as when TNP-TGG was present throughout the 5 d of culture, reflecting induction of a tolerant state. Amounts of conjugate in the concentration range that have been shown by others to tolerize immature or neonatal B cells or mature B cells that have been stripped of surface IgD were sufficient to induce tolerance. The target cells being tolerized did not bear IgD, as determined by B cell depletion and blocking procedures with anti IgD. Whether the lack of surface IgD on the primed cells contributed to the relative ease of tolerance induction was not established by these studies, but the advantages of using primed B cells to examine further the role of surface IgD in tolerance susceptibility was discussed.

The subcellular distribution of adenylate and guanylate cyclases in murine lymphoid cells

Membrane vesicles can be prepared from murine lymphoid cells by nitrogen cavitation and fractionated by sedimentation through nonlinear sucrose density gradients. Two subpopulations of membrane vesicles, PMI and PMII, can be distinguished on the basis of sedimentation rate. The subcellular distribution of adenylate and guanylate cyclases in these membrane subpopulations have been compared with the distribution of a number of marker enzymes. Approximately 20-30% of the total adenylate and guanylate cyclase activity is located at the top of the sucrose gradient (soluble enzyme), the remainder of the activity being distributed in the PMI and PMII fractions (membrane-bound enzyme). More than 90% of the 5'-nucleotidase and NADH oxidase activities detected in lymphoid cell homogenates are located in PMI and PMII fractions, whereas succinate cytochrome c reductase activity is detected only in the PMII fractions. In addition, beta-galactosidase activity is distributed in the soluble and PMII fractions of the sucrose density gradients. On the basis of the fractionation patterns of these various enzyme activities, it appears that PMI fractions contain vesicles of plasma membrane and endoplasmic reticulum, whereas PMII fractions contain mitochondria, lysomes, and plasma membrane vesicles. Approximately 30-40% of the adenylate and guanylate cyclase activities in PMII can be converted to a PMI-like form following dialysis and resedimentation through a second nonlinear sucrose gradient. Adenylate and guanulate cyclases can be distinguished on the basis of sensitivity to nonionic detergents.

Specific unresponsiveness in nude mice given antigen before T cells

Nude mice given antigen before being given congenic T cells are specifically tolerant to that antigen and recovery of the ability to respond takes at least 2 weeks. If, after giving antigen, spleen cells are transferred to irradiated congenic recipients together with normal congenic thymocytes, the recipients usually remain unresponsive. Treatment of the spleen cells with supernatant from lysed cells renders them responsive in transfer. Spleen cells from unresponsive mice do not suppress normal spleen cells in transfer and the unresponsiveness is not broken by allogeneic cells. It is therefore probable that this is a case of reversible blocking of the B cell receptors and that T cells are not involved.

Separation of antigen-specific lymphocytes. II. Enrichment of hapten-specific antibody-forming cell precursors

Normal spleen cells were separated in dishes coated with thin layers of DNP-gelatin or NIP-gelatin into binding and nonbinding cells and stimulated in vitro with DNP- and/or NIP-conjugated polymerized flagellin (POL). Hapten-specific unresponsiveness was induced in the binding cell population by melting the gel at 37 degrees C or in unfractionated cells by pretreatment with soluble hapten-gelatin and could be reversed by treatment with collagenase. A specific enrichment of anti-DNP and anti-NIP antibody-forming cell precursors (AFCP) could be demonstrated in the binding cell populations after treatment with collagenase in cultures with or without "feeder" cells. However, the response of small numbers of unfractionated and purified hapten-specific spleen cells was suboptimal even in the presence of mitomycin-treated or irradiated feeder cells. Optimal numbers of anti-DNP (anti-NIP) antibody-forming cells were generated by small numbers of normal or purified spleen cells in the presence of spleen cells depleted of anti-DNP (anti-NIP) AFCP. In this system the response of only 2 times 10-4 purified hapten-specific cells was higher than the response of 10-6 unfractionated cells. Purified DNP-specific cells responded only to DNP-POL but not to NIP-POL and purified NIP-specific cells responded only to NIP-POL but not to DNP-POL. The degree of enrichment of anti-DNP AFCP decreased with increasing numbers of binding cells. NIP3-gelatin layers bound four to five times less spleen cells than DNP2-gelatin layers and the enrichment of anti-NIP AFCP (about 300-fold) was three times greater than the enrichment of anti-DNP AFCP (about 100-fold). The immunological significance of hapten-gelatin binding cells which apparently failed to respond to antigen is discussed.

The in vitro induction of immunological tolerance in the B lymphocyte by oligovalent thymus-dependent antigens

B-cell tolerance has been induced by oligovalent thymus-dependent antigens in an entirely in vitro system. Dissociated spleen cells from congenitally athymic (nu/nu) mice were preincubated for 24 h with 0.1 -- 1 mg/ml of either fowl gamma globulin (FGG) of DNP-human gamma globulin (DNP-HGG). After washing, the cells were tested for the ability to mount in vitro, thymus-independent responses against FGG and DNP. A state of specific responsiveness to either FGG or DNP was thus demonstrated. Features of this wholly in vitro system that paralleled previous findings on the in vivo induction of B-cell tolerance in nu/nu mice were the kinetics, 24 h being required for tolerance induction in either case, the abrogation of tolerance induction by the presence of POL both in vivo and in vitro, and finally the observation that in neither case was there a requirement for the antigens to be deaggregated. It was shown that DNP-(Fab) 2 fragments prepared from HGG induced DNP-specific tolerance indicating that the Fc piece was not required for tolerance induction in this in vitro system. DNP-bovine serum albumin was less effective than DNP-HGG or DNP-(Fab)2. Preincubation with subtoxic concentrations of DNP-lysine of DNP-epsilon-capric acid had only a marginal effect on DNP responsiveness. Since nu/nu mice, lacking in detectable T-cell function, were used as spleen cell donors, this work provides further evidence that B-cell tolerance to thymus-dependent antigens can be induced without the participation of T cells. It is suggested that B-cell tolerance to thymus-dependent antigens occurs when the antigen in a sufficient concentration and over a sufficient period of time has direct access to the B cell. This contact with antigen must be in the absence of an additional influence provided either by adjuvants like endotoxin or POL, or by activated macrophages, which may be stimulated by activated T cells; otherwise not tolerance but B-cell activation will occur.

The influence of intracellular levels of cyclic nucleotides on cell proliferation and the induction of antibody synthesis

The intracellular ratio of adenosine 3',5'-cyclic monophosphate (cyclic AMP) to guanosine 3',5'-cyclic monophosphate (cyclic GMP) may control the developmental pathway followed by antibody-forming cell (AFC) precursors. The evidence for this is derived from several different types of experiments. First lipopolysaccharide (LPS) which is mitogenic for B lymphocytes, stimulates rapid, transient changes in intracellular levels of cyclic GMP but not cyclic AMP when added to mouse spleen cultures. Cyclic GMP itself stimulates DNA synthesis in these cultures, suggesting that the intracellular changes in cyclic GMP levels are involved in the mitogenic signal delivered by LPS to cells. The absolute amounts of cyclic nucleotides may vary widely in different cells under various conditions, however, the intracellular ratio of cyclic AMP to cyclic GMP is always high in nondividing cells and low in dividing cells. AFC precursors appear to respond to antigen in the absence of T-cell activity by inactivation (1-7). In the response to antigen in the presence of specific T cells, precursor cells proliferate and mature to AFC. Raising intracellular levels of cyclic AMP inhibits cell proliferation and leads to precursor cell inactivation (14, 15). It is suggested that the interaction of antigen with immunoglobulin receptors on the surface of precursors cells leads to the stimulation of adenylate cyclase activity and initiates the inactivation pathway. Since cyclic GMP stimulates immune responses in T-cell-depleted cultures (14, 15) and increasing cyclic GMP levels appear to be involved in the delivery of a mitogenic signal to cells, it is suggested that T-helper cells deliver a signal to precursor cells via the stimulation of guanylate cyclase to initiate the inductive pathway. It is suggested that it is the intracellular ratio of cyclic AMP to cyclic GMP that regulates the fate of precursor cells, not the absolute level of one cyclic nucleotide.

Genetic control of immune responses in vitro. 3. Tolerogenic properties of the terpolymer L-glutamic acid 60-L-alanine30-L-tyrosine10 (GAT) for spleen cells from nonresponder (H-2s and H-2q) mice

Although nonresponder, H-2(s) and H-2(q), mice fail to develop GAT-specific PFC responses to GAT, they do develop GAT-specific PFC responses when stimulated by GAT complexed to an immunogenic carrier such as methylated bovine serum albumin. The studies described in this paper show that injection of nonresponder mice with GAT specifically decreases their ability to develop anti-GAT PFC responses to a subsequent challenge with GAT-MBSA. Addition of GAT to cultures of spleen cells from nonresponder mice also prevents development of the GAT-specific PFC responses stimulated by GAT-MBSA. Thus, interaction of nonresponder spleen cells with GAT leads to the induction of unresponsiveness in vivo and in vitro. Various parameters of the tolerance induction have been investigated and described. A comparison of the effects of GAT on B cells indicates that nonresponder B cells are more readily rendered unresponsive by soluble GAT than are responder B cells. The significance of these data for our understanding of Ir gene regulation of the immune response is discussed.

Genetic control of immune responses in vitro. IV. Conditions for cooperative interactions between nonresponder parental B cells and primed (responder plus nonresponder) F1 T cells in the development of an antibody response under Ir gene control in vitro

The conditions for cooperative interactions between nonresponder B10.S B cells and GAT-primed irradiated (C57BL/6 x SJL)F(1) T cells in the response by cultures of mouse spleen cells to GAT were investigated. GAT-specific antibody responses could be elicited by soluble GAT in cultures of GAT-primed irradiated (C57BL/6 x SJL)F(1) T cells with C57BL/6 B cells but not with B10.S B cells. In contrast, when GAT was presented to the cultures on F(1) macrophages or as aggregates of GAT with MBSA, GAT-specific PFC responses were observed with both B10.S or C57BL/6 B cells. Irradiated GAT-primed T cells were nevertheless essential for the development of these responses. The GAT-specific response of B10.S B cells in these cultures was inhibited by the addition of soluble GAT at culture initiation. These results indicate that genetic disparity at Ir loci is not an absolute barrier to T-B-cell cooperative interactions in the response to antigens under Ir gene control. The significance of these data for the function of Ir gene products in immunocompetent cells is discussed.