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Biomedical subjects

H Waldmann

Publications and source records attributed to H Waldmann.

At least 271 records · Page 15Linked to original sources
PubMed1989

Resistance to experimental autoimmune thyroiditis: L3T4+ cells as mediators of both thyroglobulin-activated and TSH-induced suppression.

Mechanisms suppressive to induction of murine experimental autoimmune thyroiditis (EAT) can be activated by pretreatment with tolerogenic doses of mouse thyroglobulin (MTg) or prior TSH infusion to raise circulatory MTg levels. MTg-activated suppressor T cells (Ts), shown earlier to be Thy-1+ and probably I-J+, were further characterized by in vivo administration of paired rat monoclonal antibodies to distinct epitopes on the L3T4 or Lyt-2 molecule, either on the day of, or subsequent to, initiation of the tolerogenic regimes. The cells required at the time of MTg pretreatment were L3T4+, Lyt-2- and low anti-L3T4 doses had no effect on their activation. The cells that mediated the strong MTg-induced resistance following pretreatment were also L3T4+; their suppressor function could only be abrogated by depletion of L3T4+, but not Lyt-2+, cells. Injection of cyclophosphamide (20-100 mg/kg) either prior to EAT induction or after Ts activation did not affect the severity of disease. Similarly, the suppressor state evoked by TSH infusion could only be abrogated by anti-L3T4 treatment. These findings indicate that both MTg-activated and TSH-induced suppression are mediated by L3T4+ cells. We hypothesize that MTg-specific Ts are present in normal, EAT-susceptible mice in low numbers to contribute to the maintenance of self-tolerance and that they are stimulated by increased levels of circulatory MTg to expand/differentiate and mediate the marked resistance to EAT induction.

Animals↗
PubMed1989

A repertoire of monoclonal antibodies with human heavy chains from transgenic mice.

The introduction of human immunoglobulin gene segments in their unrearranged configuration into the germ line of mice might allow the production of a repertoire of human antibodies. Such transgenic mice could be used for the production of human monoclonal antibodies against human antigens. To test the feasibility of this approach, mice were created that carry a human heavy-chain minilocus comprising unrearranged immunoglobulin variable, diversity, and joining elements linked to a human mu-chain gene. The gene segments of this minilocus are rearranged in a large proportion of cells in thymus and spleen but not in nonlymphoid tissue. Some 4% of the B lymphocytes synthesize human mu chains resulting in a serum titer of about 50 micrograms of transgenic IgM antibody per ml. Hybridomas were established from the transgenic mice that stably secreted several micrograms of antibodies containing human mu heavy chains per milliliter.

Animals↗
PubMed1989

T cell depletion of human bone marrow. Comparison of Campath-1 plus complement, anti-T cell ricin A chain immunotoxin, and soybean agglutinin alone or in combination with sheep erythrocytes or immunomagnetic beads.

The aim of this study was to compare the extent of in vitro T cell depletion and recovery of hematopoietic progenitor cells achieved with five methods of T cell depletion. Bone marrow samples from the same source were treated with monoclonal antibody Campath-1 (CP1) and human complement, XomaZyme-H65 (anti-T cell ricin A chain immunotoxin), or soybean agglutinin (SBA) alone or in combination with sheep erythrocytes (EAET) or a cocktail of immunomagnetic beads (B) directly coated with anti-CD2, anti-CD3, or anti-CD8 monoclonal antibodies. Residual T cells were enumerated by limiting dilution analysis, EAET rosetting, and proliferative responses to phytohemagglutinin. The results of this study demonstrated the following reductions in BM T cells as detected by limiting dilution analysis (mean % control): SBA+B (99.9%), SBA+EAET (99.8%), CP1+C' (99.4%), anti-T cell ricin A chain immunotoxin (99.0%), and SBA alone (94.2%). Neither PHA response nor enumeration of residual EAET rosettes provided discriminating differences in the degree of T cell depletion by treatment method when T cell reductions exceeded 99.0% by LDA. These results demonstrate the ability of CP1+C', XomaZyme-H65, and SBA plus sheep erythrocyte or magnetic bead depletion to achieve a greater than 99% reduction of BM T cells and the importance of limiting dilution analysis in defining differences in T cell numbers when depletion exceeded 99%.

Animals↗
PubMed1989

Campath-1M--prophylactic use after kidney transplantation. A randomized controlled clinical trial.

Campath-1M is a rat monoclonal IgM antibody that binds human complement and recognizes virtually all peripheral human mononuclear cells. It is known to be effective in T cell depletion of bone marrow grafts, and encouraging results were obtained in a pilot study in which the antibody was used in prevention and treatment of rejection of kidney, pancreas, and liver allografts. In this randomized controlled clinical trial, Campath-1M has been evaluated as a prophylactic agent following renal allografting. It is shown that patients who received a 10-day course of the antibody immediately postoperatively, in addition to standard therapy with high-dose cyclosporine (17 mg/kg), experienced a significantly lower incidence of early acute cellular rejection than control patients who received cyclosporine alone. There was no evidence of "rebound" rejection following the end of antibody treatment to suggest that rejection had merely been delayed. However, patients who received this additional immunosuppression experienced a significantly higher incidence of serious infections than controls, this negating any benefit from the treatment in terms of graft survival. Thus, a monoclonal antibody of broad specificity directed against lymphocytes may be effective as a prophylactic agent after organ transplantation but its use should be accompanied by a reduction in other immunosuppressive drugs.

Antibodies, Monoclonal↗
PubMed1989

Beneficial effect of monoclonal antibody to interleukin 2 receptor on activated T cells in rheumatoid arthritis.

Campath 6, a rat IgG2b monoclonal antibody to the interleukin 2 receptor on activated T cells, was used to treat three patients with active rheumatoid arthritis unresponsive to conventional treatment. Two patients had an excellent response for about three months. There were no significant side effects. The results suggest that activated T cells are of importance in the pathogenesis of rheumatoid arthritis. Although infusions of rat monoclonal antibodies could not be repeated because of the risk of sensitisation, the development of humanised monoclonal antibodies targeted against specific T cell sets would allow repeated courses of treatment to be given.

Adult↗
PubMed1989

Resistance to collagen-induced arthritis in DBA/1 mice by intraperitoneal administration of soluble type II collagen involves both CD4+ and CD8+ T lymphocytes.

In this paper we report that intraperitoneal administration of type II collagen in a soluble form protects DBA/1 mice against collagen-induced arthritis (CIA) on subsequent arthritogenic challenge with soluble type II collagen in adjuvant. The degree of arthritis suppression, which is expressed in terms of reduced incidence of arthritis, delayed onset and reduced anti-collagen antibody titres, depends on the dose and timing of the pre-immunization collagen injection. In order to elucidate the rôles of CD4+ and CD8+ T lymphocytes subsets in arthritis resistance we administered monoclonal antibodies (mAb) to these antigenic determinants around the time of immunization with soluble type II collagen. Anti-CD4 mAb caused abrogation of arthritis resistance while anti-CD8 mAb was less effective. However, administration of anti-CD8 mAb two weeks after pre-immunization with soluble collagen was very effective in reversing arthritis resistance. From these findings we conclude that CD4+ and CD8+ T cells are involved in resistance to arthritis though the relative importance of each subset changes during the course of the process leading to resistance to CIA.

Animals↗
PubMed1989

Adoptive suppression of erythrocyte autoantibodies in Lyt-2+ depleted recipients.

Cells suppressing red blood cell (RBC) autoantibody responses were found to exert their effect in Lyt-2+ depleted recipients. Mice injected with monoclonal antibodies to Lyt-2 became deficient in Lyt-2+ cells as judged by indirect immunofluorescence. These mice and normal recipients were given either rat RBC primed spleen cells (suppressor cells) or normal spleen cells and challenged with rat RBC. The autoantibody response of both Lyt-2+ depleted and normal recipients was suppressed as compared with that of mice given normal spleen cells. It is suggested that an Lyt-1+ cell may be involved in the expression of suppression.

Animals↗
PubMed1989

Pathogenic mechanisms in murine autoimmune thyroiditis: short- and long-term effects of in vivo depletion of CD4+ and CD8+ cells.

Both murine CD4+ and CD8+ cells are found in the thyroid infiltrate in experimental autoimmune thyroiditis (EAT) induced with mouse thyroglobulin (MTg). MTg activation of immune cells in vitro enables CD4+ cells to transfer thyroiditis adoptively and to aid the cytotoxic capacity of CD8+ cells for thyroid monolayers. To dissect their relative contribution to pathogenesis in vivo, depleting doses of paired rat monoclonal antibodies (MoAb) recognizing two distinct CD4 or CD8 epitopes were injected alone or in combination. Early treatment with CD4 MoAb interfered with the induction and development of EAT, whereas similar treatment with CD8 MoAb reduced infiltration moderately and did not enhance antibody response. To examine the long-term effect of therapy on advancing EAT, administration of MoAb was delayed to days 21 and 25, and thyroids were analysed immunohistochemically on days 28 and 70. Whereas control mice showed about 30% CD4+ and CD8+ cells at a 2:1 ratio (the remainder being mostly macrophages) on both days 28 and 70, the CD4 therapy regime led to reduced severity and the lesions on day 70 contained very low percentage of CD4+ cells, but elevated percentage of CD8+ cells (ratio 1:3.5). The CD8 therapy regime led to reduced CD8+ cells without changing the range of CD4+ cells (ratio 4:1). Thus, subset involvement may be influenced by the MoAb used. When CD4 and CD8 MoAb were combined, greater than 50% of the thyroids were cleared of all inflammatory cells; lesions when found were very small and contained less than 10% T cells (ratio 1:1). Since emerging T cells were not retained in the thyroid despite ongoing antigenic stimulus leading to increased antibody titres, the therapeutic effect of MoAb, even at an advanced stage of disease, was long lasting.

Animals↗
PubMed1989

A role for CD4+ but not CD8+ T cells in immunity to Schistosoma mansoni induced by 20 krad-irradiated and Ro 11-3128-terminated infections.

The role of CD4+ (L3/T4+) and CD8+ (Lyt-2+) T cells in immunity to Schistosoma mansoni induced by 20 krad-irradiated and Ro 11-terminated infections in mice was investigated directly by in vivo depletion of these subsets with cytotoxic rat monoclonal antibodies (mAb). Effective physical depletion was demonstrated by flow cytometric analysis and immunohistochemical staining. Functional depletion of helper activity following anti-CD4 treatment was indicated by an abrogation of concanavalin A(Con A)-induced colony-stimulating factor (CSF) release, while anti-CD8 treatment had no effect in these assays. Pre-existing S. mansoni-specific antibody levels were unaffected by anti-CD4 and anti-CD8 treatment. In vivo depletion of CD4+ T cells resulted in a dramatic reduction in immunity induced by one (up to 100%) and two (up to 70%) vaccinations with 20 krad-irradiated cercariae and also of resistance induced by Ro 11-attenuated infections (up to 100%). Depletion of CD8+ T cells had no effect on resistance induced by any of the vaccination protocols investigated. A correlation was observed between resistance and T cell-induced, macrophage-mediated killing of schistosomula in vitro, both of which were abrogated following anti-CD4 treatment but were unaffected by CD8+ T-cell depletion. The possible role of CD4+ T cells in vivo and the implications for vaccine development are discussed.

Animals↗
PubMed1989

Effect of CD4 monoclonal antibody in vivo on lesion development, delayed-type hypersensitivity and interleukin 3 production in experimental murine cutaneous leishmaniasis.

Highly susceptible BALB/c mice subjected to adult thymectomy followed by prolonged (15 weeks), twice-weekly injections of a low dose (100 micrograms) of CD4 monoclonal antibody (MoAb) develop resistance to otherwise uniformly fatal and disseminating Leishmania major infection. In contrast, similar treatment with CD8 MoAb has no effect on the course of L. major infection. CD4 MoAb administered after the lesion establishment also has no effect. Mice which become resistant following CD4 MoAb treatment developed the classical delayed-type hypersensitivity (DTH) which persisted at 72 h after footpad injection with killed L. major promastigotes. A substantial degree of resistance can also be induced in the BALB/c mice with two i.v. high doses of 500 micrograms of CD4 MoAb given immediately prior to L. major infection. The treated mice developed classical DTH and significantly smaller lesions. The spleen cells from these mice also produced significantly lower levels of IL-3 compared to that of untreated control mice when cultured with L. major antigens in vitro. In contrast, genetically resistant CBA mice treated with CD4 MoAb developed significantly larger lesions but lower levels of classical DTH compared to untreated mice. These data confirmed and extended earlier reports on the prophylactic effect of CD4 MoAb in susceptible BALB/c mice and the disease exacerbative effect in the resistant CBA mice. The data also further illustrate the direct correlation between classical DTH and resistance, and the inverse correlation between IL-3 production and resistance in experimental cutaneous leishmaniasis.

Animals↗
PubMed1988

Remission induction in non-Hodgkin lymphoma with reshaped human monoclonal antibody CAMPATH-1H.

A genetically reshaped human IgG1 monoclonal antibody (CAMPATH-1H) was used to treat two patients with non-Hodgkin lymphoma. Doses of 1-20 mg daily were given intravenously for up to 43 days. In both patients lymphoma cells were cleared from the blood and bone marrow and splenomegaly resolved. One patient had lymphadenopathy which also resolved. These effects were achieved without myelosuppression, and normal haemopoeisis was restored during the course of treatment, partially in one patient and completely in the other. No antiglobulin response was detected in either patient. CAMPATH-1H is a potent lympholytic antibody which might have an important use in the treatment of lymphoproliferative disorders and additionally as an immunosuppressive agent.

Aged↗
PubMed1988

Human monoclonal IgG isotypes differ in complement activating function at the level of C4 as well as C1q.

Humanized antibodies are likely to have a major role in therapy and it is important to define their interaction with physiological effectors. By comparing a matched series of chimeric human mAbs we found that igG1 was most efficient in complement lysis, although IgG3 bound more C1q. To resolve this paradox we compared the ability of human IgG1, IgG2, IgG3, IgG4, and IgE and rat IgG2b to cause C1q binding, C1 binding and activation, C4 activation, C4b binding, and C3b binding. Rat IgG2b was included because this isotype has already successfully been used for therapy. Human IgG1 was less efficient than IgG3 and fixing C1q and C1 on the cell surface, but the number of C4 molecules bound per C1 was 10-fold greater for IgG1 than for IgG3. This difference, amplified through later stages of the complement cascade, can account for the superiority of IgG1 for cell lysis. The efficiency of IgG1 in fixing C4 was not due to a favored binding site on the antibody molecule, since virtually all of the bound C4b was attached to the cells. Rather, it appeared that the activation of C4 by C1s was greatly favored by IgG1 compared with IgG3. It should be possible to combine the optimal properties of IgG1 and IgG3 antibodies to produce an improved therapeutic reagent.

Antibodies, Monoclonal↗
PubMed1988

Reshaping human antibodies for therapy.

A human IgGI antibody has been reshaped for serotherapy in humans by introducing the six hypervariable regions from the heavy- and light-chain variable domains of a rat antibody directed against human lymphocytes. The reshaped human antibody is as effective as the rat antibody in complement and is more effective in cell-mediated lysis of human lymphocytes.

Amino Acid Sequence↗
PubMed1988

Mechanisms of monoclonal antibody-facilitated tolerance induction: a possible role for the CD4 (L3T4) and CD11a (LFA-1) molecules in self-non-self discrimination.

In vivo therapy with a CD4 (L3T4) monoclonal antibody is able to provide a tolerogenic milieu for a limited number of protein antigens. In this study we have analyzed the mechanisms of such tolerance to human gamma globulin, and show that tolerance is induced in adult T helper cells without a need for cellular depletion, and that it is probably not maintained by suppressor mechanisms nor by regulatory cellular circuits involving CD8+ (Ly-2+) cells. Tolerance induction is not a property peculiar to the CD4 molecule, as similar effects can be elicited with a monoclonal antibody directed to the CD11a (LFA-1) molecule. We suggest that tolerance is maintained by the functional deletion of mature T helper cells and that adhesion molecules, such as CD4, CD8 and CD11a, may play a critical role in T cell discernment of self from nonself.

Animals↗
PubMed1988

Importance of antigen specificity for complement-mediated lysis by monoclonal antibodies.

Lysis of human lymphocytes by autologous complement had been studied using a range of monoclonal antibodies against different antigens. Antigen specificity (and not antibody isotype) was the most important factor which influenced cell lysis and this could not be accounted for merely by differences in surface density between antigens. Three antigens with comparable surface density were studied in detail: CAMPATH-1 (lytic), major histocompatibility complex class I (lytic) and leukocyte common antigen (poorly lytic). C1q binding was roughly proportional to antibody binding and dependent on antibody isotype. However, the lytic antibodies were much better able to bind and activate whole C1 than the poorly lytic ones. This result would not have been predicted from traditional concepts of complement activation but can be interpreted in the light of models for C1 activation which involve Fc-Fc interactions, Fc-C1r2s2 interactions and a critical C1q stem-arm angle for C1 binding and activation.

Antibodies, Monoclonal↗