Search PubMed⌕ Search

Biomedical subjects

H Waldmann

Publications and source records attributed to H Waldmann.

At least 253 records · Page 14Linked to original sources
PubMed1990

Induction of tolerance in peripheral T cells with monoclonal antibodies.

Our goal has been to develop ways to tolerize the mature immune system to any defined antigen. In this report we show that peripheral (post-thymic) T cells of mice can become tolerant to a range of antigens (human and rat immunoglobulins, and bone marrow and skin grafts that differ at multiple minor transplantation antigens). In the case of human gamma globulin (HGG), this required that the antigen be given under the cover of a short course of non-depleting anti-CD4 antibody, while for tolerance to skin and marrow grafts anti-CD8 antibody was also required. Tolerance to HGG could be reinforced by repeated injections of HGG, but was lost in the absence of any further exposure to antigen. This reversal of tolerance with time was due to new T cells being exported from the thymus, as it was not observed in tolerized, adult thymectomized mice. In contrast, tolerance to marrow and skin grafts was permanent, presumably because the established grafts acted as a continuous source of antigen to reinforce the tolerant state. Tolerance could not be broken by the infusion of unprimed spleen cells and in one example (tolerance to Mls-1a) there was clear evidence that specific peripheral T cells were anergic. We propose that anergic cells may themselves participate in reinforcing the tolerant state by competing at sites of antigen presentation.

Animals↗
PubMed1990

The induction of skin graft tolerance in major histocompatibility complex-mismatched or primed recipients: primed T cells can be tolerized in the periphery with anti-CD4 and anti-CD8 antibodies.

Mice given short courses of anti-CD4 and anti-CD8 monoclonal antibodies became tolerant of allogeneic skin grafted at the same time. Tolerance could be obtained without T cell depletion across multiple minor antigen mismatches, both in naive and primed animals, demonstrating that peripheral T cells could be tolerized, even if they had been previously activated. Where donor and recipient were incompatible across the whole major histocompatibility complex, specific tolerance could be achieved by using a combination of depleting followed by non-depleting antibodies, where each alone was unsuccessful. Although mice clearly tolerated their original skin grafts, we observed in some strain combinations that a second fresh, but genotypically identical graft, was slowly rejected. Such mice also possessed T cells which could proliferate to donor-type stimulator cells in vitro. Whatever the mechanisms, we have demonstrated that operational transplantation tolerance can be achieved with simple, non-toxic antibody therapy. The introduction of comparable tolerance-inducing regimens in clinical organ transplantation could obviate the need for long-term immunosuppression and its unfortunate side effects.

Animals↗
PubMed1990

Characterization of effector cells of graft vs leukemia following allogeneic bone marrow transplantation in mice inoculated with murine B-cell leukemia.

It is now widely accepted that immunocompetent lymphocytes in allogeneic bone marrow grafts exert an antileukemic effect that contributes to the cure of leukemia. Graft vs leukemia (GVL) effects independent of graft vs host disease were investigated in allogeneic bone marrow chimeras tolerant of host and donor alloantigens. The role of Thy1.2, L3T4 and Lyt2 T lymphocytes as effector cells of GVL were investigated in (BALB/c x C57BL/6)F1 mice inoculated with murine B-cell leukemia and subsequently conditioned with total lymphoid irradiation and cyclophosphamide (200 mg/kg). Mice were reconstituted with C57BL/6 bone marrow cells depleted of well-defined T-cell subsets or enriched for stem cells by the soybean agglutination method. Detection of residual tumor cells, an indicator for efficacy of GVL, was carried out by adoptive transfer of peripheral blood or spleen cells obtained from treated chimeras into secondary naive BALB/c recipients at different time intervals following bone marrow transplantation. Treatment of the primary marrow inoculum with monoclonal anti-Thy1.2 or anti-Lyt2 abolished the GVL effects and all secondary BALB/c recipients developed leukemia within 60 days. On the other hand, the treatment with monoclonal anti-L3T4 did not influence the effect of GVL and all treated recipients remained without leukemia. The data suggest that T cells may mediate GVL effects in the absence of graft vs host disease and in circumstances where tolerance to conventional alloantigens is elicited. Effector cells of GVL across the major histocompatibility complex (MHC) in the murine B-cell leukemia tumor model system appear to be Thy1.2+ Lyt2+ L3T4-. Induction of GVL effects by allogeneic cells tolerant of host MHC suggests that these effects may be independent of graft vs host disease.

Agglutinins↗
PubMed1990

The involvement of Ly2+ T cells in beta cell destruction.

The non-obese diabetic (NOD) mouse is considered to be a good model of human Type I diabetes mellitus. Both sexes develop insulitis starting at about 6 weeks of age, and onset of diabetes follows at about 30 weeks in females, but later and much less frequently in males. In some mice (but not all) infiltration of the islets leads to selective destruction of insulin-producing beta cells, which is marked by clinically overt diabetes and is thought to be an autoimmune response mediated by T cells. Both L3T4+ and Ly2+ cells have been implicated in the destructive process and we have used an in vivo transfer system, together with histological studies on the pancreas, to demonstrate the essential role played by Ly2+ T cells in the destruction of beta cells in diabetic mice.

Animals↗
PubMed1990

Synthetic tumor-associated glycopeptide antigens.

Glycopeptides with TN antigen (GalNAc)Ser/Thr and T-antigen structures (beta Gall-3GalNAc)Ser/Thr, described as tumor-associated antigens, were synthesized and coupled to bovine serum albumin. Alternatively, synthetic methods for the construction of beta-anomeric analogues of the TN and T-antigen glycopeptides were developed, aiming at antigenic structures having a varied stereochemistry of the linkage between the carbohydrate and the peptide moiety. As a further type of potential tumor-associated antigen, fucosyl-chitobiose asparagine glycopeptides were synthesized, deprotected, and coupled to bovine serum albumin. The chemical methods developed now make the complex sensitive glycoprotein partial structures accessible in analytically pure form and in preparative amounts.

Amino Acid Sequence↗
PubMed1990

Human protectin (CD59), an 18,000-20,000 MW complement lysis restricting factor, inhibits C5b-8 catalysed insertion of C9 into lipid bilayers.

Human cells are relatively resistant to lysis by the homologous complement system. Here we describe the mechanism of action of a recently discovered and widely distributed 18,000-20,000 molecular weight (MW) membrane glycoprotein (CD59), which appears to act as a major protective element against complement-mediated lysis (hence called protectin). When incorporated into heterologous erythrocyte membranes, protectin efficiently prevented cell lysis by human serum. Neutralization with antibody of the naturally occurring protectin on human erythrocytes or on nucleated K562 cells increased their susceptibility to lysis by homologous complement. During complement activation, protectin became incorporated into the membrane attack complex (MAC). By interacting with newly exposed regions in the C5b-8 complex and in aggregating C9 it limited the number of C9 molecules associating with the C5b-8 complex to a C8:C9 ratio of 1:1.5 instead of a normal average of 1:3.5. The results demonstrate directly that protectin is a powerful inhibitor of complement cytolysis and acts by inhibiting the C5b-8 catalysed insertion of C9 into the lipid bilayer.

Antigens, Differentiation↗
PubMed1990

Reprogramming the immune system for tolerance with monoclonal antibodies.

Monoclonal antibodies to CD4, CD8 and CD11a can be used in vivo either to deplete or functionally block T cells to create a tolerance permissive environment. Short courses of non-depleting CD4 and CD8 antibodies were used to induce tolerance separately in CD4+ and CD8+ T cells either to foreign immunoglobulins, bone marrow, or skin grafts. Tolerance was obtained to minor (non-MHC) transplantation antigens without T cell depletion even in actively sensitized mice, or to MHC plus minor antigens presented directly by skin grafts using combinations of depleting followed by blockading CD4 and CD8 antibodies. In all cases, tolerance was specific to the antigen/tissue given under cover of antibody treatment, and in one example it could be shown that T cells directed to MLS-1a had been forced into an anergic state. This induction of tolerant, anergic T cells in the periphery is able to explain many of the features associated with tolerance, not only in the model systems using foreign antigens, but also in the normal regulation of anti-self responses and its failure in autoimmune diseases. It is our new found ability to use antigen under the cover of antibody treatment to accurately control the pattern of tolerant T cells in vivo that we refer to by using the term 'reprogramming'. We also describe the clinical treatment of one patient with an autoimmune vasculitis based on the ideas developed from the mouse models.

Animals↗
PubMed1990

Purging in auto- and allografts: monoclonal antibodies which use human complement and other natural effector mechanisms.

CAMPATH-1M is a rat IgM monoclonal antibody which binds to an antigen on all human lymphocytes and monocytes, but which is not present on marrow stem cells (Hale et al., 1983). Lymphocytes can be efficiently killed in bone marrow buffy coat preparations using the antibody and donor human serum as a means to avoid graft versus host disease (GVHD) (Waldmann et al., 1984). An analysis of 520 matched sibling bone marrow transplants (BMT) for leukaemia demonstrates that T-cell depletion using CAMPATH-1M markedly reduces the incidence and severity of GVHD, but there is an increased risk of graft rejection. In the case of CGL in chronic phase, there is also an associated extra risk of relapse, particularly in patients where engraftment may have been compromised (Hale et al., 1988a). A rat IgG2b antibody of the same specificity as CAMPATH-1 (CAMPATH-1G) was developed which is able to both fix human complement and opsonize lymphocytes in vivo (Dyer et al., 1989). Initial studies for the prophylaxis of bone marrow rejection in 55 mismatched and matched unrelated donor (MUD) BMTs suggest that CAMPATH-1G treatment of the recipient may reduce, but not eliminate, marrow graft rejection. The broad CAMPATH-1 specificity means that it is also ideal for purging a range of lymphoid malignancies prior to autologous BMT, or even for direct serotherapy of leukaemic patients. However, there may be limitations of monoclonal antibody purging using complement or other natural effector mechanisms either in vivo or in vitro; in particular, antigenic modulation and an antiglobulin response. Phase 1 studies of "in vivo purging" with a monovalent CD3 antibody (Clark et al., 1989), and also with a genetically engineered humanized IgG1 (CAMPATH-1H) (Hale et al., 1988b) suggest that these limitations can be overcome.

Antibodies, Monoclonal↗
PubMed1989

The immunogenicity of chimeric antibodies.

Mice were immunized with model xenogeneic (both the VH frameworks and the CH domains of human origin), chimeric (just VH frameworks human), or self antibodies, and the antiantibody responses were dissected. Only the self antibody did not elicit a response. A strong response was elicited by the most xenogeneic antibody with approximately 90% against the C and approximately 10% against the V. The anti-V response was not attenuated in the chimeric antibody, demonstrating that foreign VH frameworks can be sufficient to lead to a strong antiantibody response. The magnitude of this xenogeneic anti-VH response was similar to that of the allotypic response elicited by immunizing mice of the Igha allotype with an Ighb antibody. Thus, although chimerization can diminish antiantibody responses, attention should be paid both to V region immunogenicity and to polymorphism.

Animals↗
PubMed1989

Effect of graft perfusion with two CD45 monoclonal antibodies on incidence of kidney allograft rejection.

In a blind trial, 77 patients were randomised to receive first cadaver kidney allografts that had been perfused either with a pair of CD45 monoclonal antibodies (mAbs), in an attempt to reduce the immunogenicity of passenger leucocytes, or with control human albumin solution. No complications of mAb perfusion were observed. Patient and allograft survival were similar in both groups. Rejection episodes were recorded in 7 (18%) of the patient with mAb perfused allografts compared with 24 (63%) of the controls.

Animals↗
PubMed1989

CD59, an LY-6-like protein expressed in human lymphoid cells, regulates the action of the complement membrane attack complex on homologous cells.

A novel cell surface antigen has been identified on a wide range of lymphoid cells and erythrocytes. A mAb YTH 53.1 (CD59) against this antigen enhanced the lysis of human red cells and lymphocytes by homologous complement. Studies of reactive lysis using different species of C56, and of whole serum used as a source of C7-9, indicated that the inhibitory activity of the CD59 antigen is directed towards the homologous membrane attack complex. CD59 antigen was purified from human urine and erythrocyte stroma by affinity chromatography using the mAb YTH 53.1 immobilized on Sepharose, and, following transient expression of a human T cell cDNA library in COS cells, the corresponding cDNA also identified using the antibody. It was found that the CD59 antigen is a small protein (approximately 20 kD as judged by SDS-PAGE, 11.5 kD predicted from the isolated cDNA) sometimes associated with larger components (45 and 80 kD) in urine. The sequence of CD59 antigen is unlike that of other complement components or regulatory proteins, but shows 26% identity with that of the murine LY-6 antigen. CD59 antigen was released from the surface of transfected COS cells by phosphatidylinositol-specific phospholipase C, demonstrating that it is attached to the cell membrane by means of a glycolipid anchor; it is therefore likely to be absent from the surface of affected erythrocytes in the disease paroxysmal nocturnal hemoglobinuria.

Antibodies, Monoclonal↗
PubMed1989

A matched set of rat/mouse chimeric antibodies. Identification and biological properties of rat H chain constant regions mu, gamma 1, gamma 2a, gamma 2b, gamma 2c, epsilon, and alpha.

Rat C regions mu, gamma 1, gamma 2a, gamma 2b, gamma 2c, epsilon, and alpha have been characterized by means of chimeric antibody technology. A set of rat/mouse Ag-specific (anti-4-hydroxy-3-nitrophenacetyl) antibodies was constructed that differ only in the H chain constant region but carry identical V region and L chain, both of which are of mouse origin. All rat constant regions could be expressed and m.w. were as expected from the protein sequence. A slight variation in mobility within the IgG subclasses allowed us to establish a hierarchy for the sizes of the four gamma H chains; gamma 2b greater than gamma 1 greater than gamma 2c greater than gamma 2a. Rat IgG2c and IgG2b could be purified on both protein A and protein G while rat IgG2a could only be purified on protein G. Rat IgM and IgG2b were the most potent in C-mediated hemolysis. This was not simply a consequence of the amount of C1q bound because IgG2c bound C1q efficiently but was relatively poor in cell lysis. In ADCC using human effector and target cells, IgG2b and IgG1 were the most effective.

Animals↗
PubMed1989

Effects of CAMPATH-1 antibodies in vivo in patients with lymphoid malignancies: influence of antibody isotype.

The CAMPATH-1 family of antibodies recognize an abundant glycoprotein expressed on virtually all human lymphocytes. All rat IgM and IgG antibodies of this specificity are lytic with human complement, but only IgG2b is active in antibody-dependent cell-mediated cytotoxicity (ADCC). We compared the ability of IgM, IgG2a, and IgG2b to deplete lymphocytes in vivo in two patients with prolymphocytic transformation of B-cell chronic lymphocytic leukemia (CLL). The IgM (CAMPATH-1M) produced transient depletion of blood lymphocytes with consumption of complement but had no effect on solid masses or bone marrow. Similar transient depletion of blood lymphocytes was noted with the IgG2a (YTH34.5). In contrast, the IgG2b (CAMPATH-1G) produced long-lasting depletion of lymphocytes from blood and marrow and improvement in splenomegaly but no detectable changes in complement levels. These differences probably reflect the importance of Fc receptor binding for effective clearance of target cells in vivo. We treated 16 more patients with a variety of lymphoid malignancies and noted consistent effects on blood lymphocytes, marrow infiltration, and splenomegaly. At this dose level, there was comparatively little improvement in affected lymph nodes or extranodal masses. Nevertheless, the in vivo lympholytic ability of CAMPATH-1G is very potent as compared with other monoclonal antibodies (MoAbs) and may have applications in therapy of lymphoid malignancies and as an immunosuppressive agent.

Aged↗
PubMed1989

Induction of classical transplantation tolerance in the adult.

Transplantation tolerance across histoincompatibilities in multiple non-H-2 minors (B10.BR into CBA/Ca) and "minor" plus H-2D (B10.A into CBA/Ca) antigens has been achieved successfully by combined adult bone marrow transplantation and treatment with CD4 and CD8 mAbs. The tolerant state was confirmed by permanent acceptance of donor strain skin grafts, and in vitro unresponsiveness to donor cells. Tolerance was associated with partial donor chimerism to various degrees. Tolerance to minor transplantation antigens induced in this manner was restricted to recipient-type MHC. The possibility was raised that tolerance resulted, at least in part, from clonal anergy rather than deletion.

Animals↗
PubMed1989

Peripheral tolerance mechanisms prevent the development of autoreactive T cells in chimeras grafted with two minor incompatible thymuses.

The thymus has been shown to play an important role in the generation of T cell tolerance to self antigens. Developing T cells are readily tolerized to antigens which are expressed in the thymus, and it is generally thought that such thymic tolerance occurs by a mechanism of clonal deletion. We sought to examine whether T cells which initially encountered a "self antigen" post-thymically would be rendered tolerant of that antigen, and if so whether the mechanism of tolerance induction would differ from that found for thymic antigens. We constructed bone marrow radiation chimeras which were grafted with two thymus lobes differing in minor histocompatibility antigens. T cells which matured in one thymus would be tolerized to the minor histocompatibility antigens expressed in that thymus but would not encounter, and would therefore have no early opportunity of being tolerized to the minor histocompatibility antigens expressed by the other thymus. The initial encounter with the minor antigens on the second thymus would occur post-thymically. Would these T cells be tolerant or responsive to those minor histocompatibility antigens? We found that tolerance was dominant in these chimeras. The data further suggest that the mechanism responsible for tolerance induction in the periphery may differ from that which operates in the thymus.

Animals↗
PubMed1989

The improved lytic function and in vivo efficacy of monovalent monoclonal CD3 antibodies.

A series of hybrid-hybridomas were derived by the cell fusion of a CD3 antibody-secreting hybridoma with other Ig-producing cell lines. The Ig molecules secreted by these hybrid-hybridomas were fractionated by ion-exchange chromatography, and fractions containing monovalent CD3 antibodies were tested for complement-mediated lysis of T cells. Two monovalent CD3 antibodies with mixed heavy chain isotypes were very poor in lysis but, in contrast, a monovalent antibody possessing two identical rat gamma 2b heavy chains but two non-identical light chains was found to be more lytic with human complement than the parental bivalent CD3 antibody. The difference in lysis was not readily explicable in terms of a difference in complement activation at the level of C1q binding or cell-associated C3. A highly purified batch of this lytic monovalent CD3 antibody was prepared in a form suitable for in vivo therapy. In a preliminary clinical study in one patient with a T lymphoma in leukemic phase this monovalent CD3 antibody was found to be very effective in depleting CD3+ tumor cells in the peripheral blood and bone marrow. The cells in the peripheral blood were completely cleared and there was no evidence for antigenic modulation. In addition the antibody was able to reverse cell-mediated kidney rejection in three kidney graft patients. These results suggest that monovalent antibody may be effective in vivo as well as in vitro and that a fuller clinical evaluation is justified.

Adolescent↗
PubMed1989

Depletion of L3T4+ and Lyt-2+ cells by rat monoclonal antibodies alters the development of adoptively transferred experimental autoimmune thyroiditis.

To delineate the contribution of L3T4+ and Lyt-2+ cells in the pathogenesis of experimental autoimmune thyroiditis (EAT), synergistic pairs of monoclonal antibodies (mAb) to the T cell subsets were used in conjunction with the adoptive transfer of mouse thyroglobulin (MTg)-activated cells from immunized mice. Initial experiments verified the important role of L3T4+ cells in the transfer of EAT. Subsequent experiments pointed to the relative contribution of both L3T4+ and Lyt-2+ cells, depending on the stage and extent of disease development. Treatment during disease with L3T4, but not Lyt-2, mAb alone significantly reduced thyroiditis. However, in situ analysis of the cellular infiltrate in thyroid sections revealed that, after treatment with mAb, the appropriate subset was eliminated without altering the amount of the other subset in the remaining lesion. In addition, treatment during severe thyroiditis following the transfer of MTg-activated lymph node cells showed that Lyt-2 mAb alone also reduced thyroid infiltration. When the recipients were pretreated with either pair of mAb before transfer, disease development was only moderately affected. We conclude that (i) donor L3T4+ cells are the primary cells responsible for the initial transfer and development of thyroiditis; and (ii) previous in vitro cytotoxicity data, plus current monoclonal antibody treatment of disease and in situ analysis, further implicate a role for Lyt-2+ cells in EAT pathogenesis.

Animals↗