Relaxed specificity of matrix metalloproteinases (MMPS) and TIMP insensitivity of tumor necrosis factor-alpha (TNF-alpha) production suggest the major TNF-alpha converting enzyme is not an MMP.

Tumor necrosis factor-alpha is released from cells by a proteolytic cleavage. Previous work suggested that a specific, non-matrix metalloproteinase carries out this cleavage, but matrix metalloproteinases have also been implicated. In this paper, we report that none of the matrix metalloproteinases tested cleaved peptide substrates as specifically as the non-matrix metalloproteinase. A matrix metalloproteinase did process tumor necrosis factor-alpha extracted from COS cells, but neither tissue inhibitor of metalloproteinases-1 nor -2 blocked tumor necrosis factor-alpha processing by human monocytes. Moreover, tissue inhibitor of metalloproteinases-1 had at most a partial effect on the in vivo release of the cytokine in mice. We conclude that a non-matrix metalloproteinase is the major physiological tumor necrosis factor-alpha convertase.

Induction of immunological tolerance to islet allografts.

T-cell dependent activation of resting B cells involves the interaction of gp39 on T cells with its receptor, CD40, on B cells. We administered either a combination of T-cell-depleted splenic lymphocytes and anti-gp39 monoclonal antibody or antibody alone to establish islet allografts in mice without continuous immunosuppression. Fully allogeneic H-2q FVB islets were permanently accepted by chemically diabetic H-2b C57BL/6 mice provided that the recipients were pretreated with both T-cell-depleted donor spleen cells and anti-gp39 antibody. Antibody alone was less effective in prolonging allograft survival, but we did observe that anti-gp39 mAb alone can exert an independent, primary effect on islet allograft survival that was dose dependent. Targeting gp39, in combination with lymphocyte transfusion, might prove suitable for tolerance induction and allotransplantation without immunosuppression.

A metalloprotease inhibitor blocks shedding of the IL-6 receptor and the p60 TNF receptor.

Many cytokines and soluble cytokine receptors are generated by limited proteolysis of membrane-bound precursors. We have examined the ability of the recently described metalloprotease inhibitor, TNF-alpha protease inhibitor (TAPI), and other protease inhibitors to modulate shedding. The membrane-bound forms of the ligands TNF-alpha and CSF-1, the p60 TNFR and the IL-6R, were expressed in COS-7 cells. As expected, TAPI blocked the spontaneous and PMA-induced release of TNF-alpha from transfected cells. Interestingly, TAPI also inhibited the release of soluble forms of p60 TNFR and IL-6R in COS-7 cells. However, the processing of CSF-1, which also requires proteolytic cleavage of a membrane protein, was not affected. The ability of TAPI to inhibit shedding was unique, since several other classes of protease inhibitors, including three other metalloprotease inhibitors, did not inhibit shedding of IL-6R. To determine whether TAPI would prevent shedding under more physiologic conditions, we demonstrated that TAPI was able to prevent unstimulated and PMA-induced release of the soluble forms of TNF-alpha, p60 TNFR, and IL-6R from the monocytic cell line, THP-1, and from human peripheral blood monocytes. In addition, TAPI was able to inhibit LPS-induced shedding of the p60 TNFR and TNF-alpha from monocytes. In summary, our results indicate that a metalloprotease or group of related metalloproteases is responsible for the proteolytic cleavage of several cell surface proteins.

Survival of mouse pancreatic islet allografts in recipients treated with allogeneic small lymphocytes and antibody to CD40 ligand.

Combined treatment with allogeneic small lymphocytes or T-depleted small lymphocytes plus a blocking antibody to CD40 ligand (CD40L) permitted indefinite pancreatic islet allograft survival in 37 of 40 recipients that differed from islet donors at major and minor histocompatibility loci. The effect of the allogeneic small lymphocytes was donor antigen-specific. Neither treatment alone was as effective as combined treatment, although anti-CD40L by itself allowed indefinite islet allograft survival in 40% of recipients. Our interpretation is that small lymphocytes expressing donor antigens in the absence of appropriate costimulatory signals are tolerogenic for alloreactive host cells. Anti-CD40L antibody may prevent host T cells from inducing costimulatory signals in donor lymphocytes or islet grafts.

Decreased CD4-CD8- TCR-alpha beta + cells in lpr/lpr mice lacking beta 2-microglobulin.

The CD4-CD8- T cells that accumulate in lpr/lpr mice have previously expressed CD8, on the basis of studies of CD8 alpha gene demethylation. The actual requirement for CD8 interaction with class I MHC molecules to promote the appearance of CD4-CD8- T cells in lpr/lpr mice has also been suggested. To examine this point in more detail, the lpr mutation was bred onto a beta 2-microglobulin-deficient background (beta 2-m-/-). C57BL/6 (B6) mice homozygous for both the lpr mutation of the fas gene and inactivation of the beta 2-m gene (beta 2-m-/- lpr/lpr) develop less alpha beta T cell lymphadenopathy than the parental B6 lpr/lpr strain. This is caused by the near absence of CD8+ T cells and a considerable reduction in CD4-CD8- T cells, revealing an important role for positive selection on class I MHC molecules during the ontogeny of lpr CD4-CD8- T cells. Although absolute numbers of peripheral T cells are decreased in beta 2-m-/- lpr/lpr mice, they manifest a B cell lymphadenopathy with age. beta 2-m-/- lpr/lpr mice display only subtle indications of autoimmune disease with age, compared with parental B6 (beta 2-m+/+)lpr/lpr mice. These include limited histopathologic stages of kidney disease and lack of proteinuria, despite the presence of serum anti-DNA Abs. Thus, absence of class I MHC-positive selection of CD8+ and CD4-CD8- TCR-alpha beta + cells limits the autoimmune diathesis observed in beta 2-m+/+ lpr/lpr mice.

The expansive role of CD40 and its ligand, gp39, in immunity.

The interactions between CD40 and its ligand, gp39, are central to the development and maintenance of immunity. The role this receptor-ligand pair plays in B cell activation, isotype switching and memory generation has been firmly established through the study of in vitro and in vivo murine models, as well as human in vitro systems and immunodeficiencies. In this review, the potential role of gp39 in the regulation of co-stimulatory molecules and their implications on thymic education and peripheral tolerance are discussed.

Collagen-induced arthritis as a model of rheumatoid arthritis.

Collagen-induced arthritis (CIA) is an animal model for the human autoimmune disease rheumatoid arthritis (RA). CIA can be induced in several species including primates by immunization with heterologous type-II collagen (CII). Polyclonal antibodies are formed upon immunization with CII that exhibit a broad range of epitope specificities (some that cross-react with hose CII); however, only antibodies directed against certain specific epitopes on CII are arthritogenic. Recently, the importance of cognate interactions between T-cells and B-cells to the induction of CIA was demonstrated by administration of monoclonal antibodies against a T-cell surface protein, gp39. Blocking the interaction of T-cell gp39, with its receptor/ligand on the surface of B-cells (CD40), completely blocked induction of CIA in mice. A concomitant reduction in the level of anti-CII IgG produced in anti-gp39-treated animals was observed, demonstrating the crucial importance of T-cell:B-cell interactions via gp39:CD-40 binding to the primary immune response to CII in vivo and therefore to the induction of CIA. Other features of CIA are important in elucidating the condition and this article will deal with some important issues.

Antibody to the ligand of CD40, gp39, blocks the occurrence of the acute and chronic forms of graft-vs-host disease.

Chronic and acute graft-versus-host disease (cGVHD and aGVHD) result from donor cells responding to host disparate MHC alleles. In cGVHD (H-2d-->H-2bd), heightened polyclonal immunoglobulin production is due to the interaction of donor allospecific helper T cells (Th) and the host B cells. In vivo administration of antibody to the ligand for CD40, gp39, blocked cGVHD-induced serum anti-DNA autoantibodies, IgE production, spontaneous immunoglobulin production in vitro, and associated splenomegaly. Antibody production remained inhibited for extended periods of time after termination of anti-gp39 administration. Antiallogeneic CTL responses induced in a GVHD were also prevented by the in vivo administration of anti-gp39 as was the associated splenomegaly. These data suggest that CD40-gp39 interactions are critical in GVHD and that CD40-gp39 may be a valuable ligand-receptor pair for targeting immunotherapeutic agents to control GVHD.

The role of CD40 in the regulation of humoral and cell-mediated immunity.

The dynamic and reciprocal communication between T helper (Th) cells and B cells appears to rely on the provision of multiple signals. The first is antigen specific and is mediated by the interaction between the T-cell receptor (TCR) and antigen bound to the major histocompatibility complex (MHC). The subsequent signals are provided by the binding of accessory molecules such as CD28 and CD40 to their respective ligands. Here, Fiona Durie and colleagues discuss the co-stimulatory role of the interaction between CD40 on B cells and CD40 ligand (CD40L, gp39) on T cells, and review evidence that suggests blocking this interaction may induce T-cell tolerance.

In vivo CD40-gp39 interactions are essential for thymus-dependent humoral immunity. II. Prolonged suppression of the humoral immune response by an antibody to the ligand for CD40, gp39.

The ligand for CD40 has been recently identified as a 39-kd protein, gp39, expressed on the surface of activated CD4+ T helper cells (Th). In vitro, soluble CD40 and anti-gp39 have been shown to block the ability of Th to activate B cells, suggesting that gp39-CD40 interactions are important to T cell-dependent B cell activation. Here it is shown that in vivo administration of anti-gp39 dramatically reduced both primary and secondary humoral immune responses to erythrocytes and soluble protein antigens without altering responses to the T-independent type II antigen, trinitrophenyl-Ficoll. Treatment of mice for 4 d with anti-gp39 inhibited the anti-sheep red blood cell (SRBC) response for at least 3 wk and inhibited the expression of all immunoglobulin isotypes in secondary responses to the protein antigen, keyhole limpet hemocyanin. To examine the direct effect of anti-gp39 on Th function, SRBC-immune Th cells from anti-gp39-treated mice were adoptively transferred and shown to be fully capable of providing help. These results suggest that anti-gp39 treatment does not cause Th deletion or anergy. Anti-gp39 may mediate its profound immunosuppressive effects on humoral immunity by blocking gp39-CD40 interactions. Moreover, these studies establish gp39-CD40 as an important receptor-ligand pair for the targeting of therapeutic antibodies to control thymus-dependent humoral responses.

Prevention of collagen-induced arthritis with an antibody to gp39, the ligand for CD40.

The ligand for the CD40 antigen is a 39-kilodalton protein, gp39, expressed on the surface of activated CD4+ T cells and is essential for thymus-dependent humoral immunity. The role of gp39-CD40 interactions in autoimmune disease was investigated in vivo with the use of an antibody that blocks their interactions (anti-gp39). Arthritis induced in mice by immunization with type II collagen was inhibited by anti-gp39. Anti-gp39 blocked the development of joint inflammation, serum antibody titers to collagen, the infiltration of inflammatory cells into the subsynovial tissue, and the erosion of cartilage and bone. Thus, interference with gp39-CD40 interactions may have therapeutic potential in the treatment of autoimmune disease.

Analysis of clonality of tumour infiltrating lymphocytes in breast cancer and uveal melanoma.

Fresh tumour infiltrating lymphocytes (TILs) from 6 uveal melanomas and 4 breast cancers were analysed by flow cytometry with a panel of 6 monoclonal antibodies to V beta regions of the T cell receptor (V betas 5a, 5b, 5c, 6, 8a and 12a). With a single exception where one TIL sample lacked V beta 12a, lymphocytes from both tumour and blood contained cells reactive with all 6 probes, and no probe was highly dominant or missing. The proportions of reactive cells differed between tumour and blood within each patient. The data indicate that while tumour infiltrating lymphocytes have a capacity to locate selectively within the tumour they nonetheless comprise a population expressing a diversity of TCR V beta genes.

Analysis of lymphocytic infiltration in uveal melanoma.

Among 27 uveal melanomas, five were found to contain tumor infiltrating lymphocytes (TILs). Four had high levels of lymphocytes, and the fifth had comparatively low levels but adequate numbers for comprehensive analysis. The TILs were analyzed by flow cytometry to determine the relative proportions of lymphocyte subsets and markers of lymphocyte activation. The results show the predominance of T-suppressor/cytotoxic lymphocytes and insignificant levels of B-cells present in the infiltrate. The T-suppressor/cytotoxic cells were generally activated to a higher degree than the T-helper cells when assayed for levels of the histocompatibility antigen, HLA-DR. T-helper cells expressed more interleukin (IL-2) receptor (Tac) than T-suppressor/cytotoxic cells.