Jordan S. Pober

Interleukin 1 acts on cultured human vascular endothelium to increase the adhesion of polymorphonuclear leukocytes, monocytes, and related leukocyte cell lines.

Increased leukocyte adhesion to the endothelial lining of blood vessels is an essential event in inflammation and the pathogenesis of certain vascular diseases. We have studied the effect of interleukin 1 (IL-1), an inflammatory/immune mediator, on endothelial-leukocyte adhesion using quantitative in vitro assays. Selective pretreatment of cultured human umbilical vein endothelial monolayers with IL-1 (5 U/ml, 4 h) resulted in an 18.3 +/- 2.6-fold increase in human peripheral blood polymorphonuclear leukocyte (PMN) adhesion (mean +/- SEM, n = 16) and a 2.6 +/- 0.3-fold increase in monocyte adhesion (n = 7) over basal levels. IL-1-treated endothelial monolayers also supported increased adhesion of the promyelocytic cell line HL-60 and the monocytelike cell line U937 (33.0 +/- 6.0-fold, n = 6 and 4.9 +/- 0.5-fold, n = 15, respectively). In contrast, selective IL-1 pretreatment of leukocytes, or the addition of IL-1 during the adhesion assay, did not alter endothelial-leukocyte adhesion. Conditioned medium from IL-1-treated endothelial cultures also did not promote leukocyte adhesion to untreated monolayers. IL-1 induction of endothelial adhesivity was concentration dependent (maximum, 10 U/ml), time dependent (peak, 4-6 h), and reversible, was blocked by cycloheximide (10 micrograms/ml) or actinomycin D (5 micrograms/ml) but not by acetylsalicylic acid (100 microM), and occurred without detectable endothelial cell damage. IL-1 treatment of SV40-transformed human endothelial cells and dermal fibroblasts did not increase their adhesivity for leukocytes. These data suggest that IL-1 can act selectively on human vascular endothelium to increase its adhesivity for circulating blood leukocytes, and thus to localize leukocyte-vessel wall interactions at sites of inflammation in vivo.

Immunoglobulin M antibodies present in the acute phase of Kawasaki syndrome lyse cultured vascular endothelial cells stimulated by gamma interferon.

Kawasaki syndrome (KS) is characterized by diffuse vasculitis and marked T cell and B cell activation. In this study, sera from 16 patients with acute KS, 15 patients in the convalescent phase of KS, and 19 age-matched controls were assessed for complement dependent cytotoxic activity against 111In-labeled human umbilical vein endothelial (HUVE) cells, Neither sera from patients with KS nor sera from controls had cytotoxic effects on HUVE cells cultivated under standard conditions. Since activated T cells such as those present in acute KS secrete gamma interferon (gamma-IFN), we also examined the effects of sera from acute KS on HUVE cells preincubated with gamma-IFN. We report here that immunoglobulin M (IgM) antibodies in sera from patients with acute KS cause significant (P less than 0.01) killing of gamma-IFN-treated HUVE cells. Pretreatment with interleukin 2, gamma-IFN, or beta-IFN failed to render HUVE susceptible to lysis with acute KS sera. The observed effects were not mediated via immune complexes. The cytotoxic antibodies in acute KS seem to be directed against inducible monomorphic antigenic determinants present on gamma-IFN-treated HUVE cells but not on control or gamma-IFN treated autologous human dermal fibroblasts (HDF). Similarly, acute KS sera also induced lysis of gamma-IFN-treated human saphenous vein endothelial (HSVE) cells but not gamma-IFN treated human saphenous vein smooth muscle (HSVSM) cells. Since gamma-IFN induces the same level of class I and class II major histocompatibility complex (MHC) antigen expression on HDF, HUVE, HSVE, and HSVSM cells, our results suggest that the anti-endothelial cell antibodies in acute KS are directed to gamma-IFN-inducible molecules other than MHC determinants. These observations are further substantiated by the failure of human B cells or monocytes to absorb the anti-endothelial cell activity. Since most vasculitides, including acute KS, are characterized both by marked immune activation and the secretion of lymphokines, antibodies directed to gamma-IFN-inducible endothelial cell antigens may represent a general mechanism for vascular injury.

Interactions of T lymphocytes with human vascular endothelial cells: Role of endothelial cells surface antigens

We have studied the interactions of peripheral blood T lymphocytes with cultured human vascular endothelial cells, focusing upon endothelial cell surface antigens important for T cell recognition. Under standard culture conditions endothelial cells express class I but not class II major histocompatibility complex (MHC) antigens. However, class II antigens may be induced by activated T cells or T cell products, including the lymphokine immune interferon. Immune interferon concomitantly increases class I antigen expression and causes a change in cell shape. In addition to vascular endothelial cells, we have found that vascular smooth muscle cells and human dermal fibroblasts may also be induced by immune interferon to express class II antigens. All known human class II antigens are induced (i.e. HLA-DR, DC and SB) as is the associated invariant chain. Induced antigen expression in these cells is stable over several days, although mRNA levels decline rapidly upon withdrawal of interferon. Vascular and stromal cell class II antigens are functional, in that they can be recognized by cytolytic and helper T cell clones. Several non-MHC antigens are also involved in the recognition of endothelial and stromal cells by T cells. We propose a model for the role of inducible class II molecules on endothelium and stromal cells in vivo: The induction of class II MHC antigens on endothelial cells, locally mediated by activated T cells, enables endothelium to present an immunogenic cell surface structure, comprised of antigen plus self class II polymorphic determinants, which in turn, serves to recruit additional antigen-specific T cells from the circulation into the site of a developing cell mediated immune response. Class II molecules on stromal cells, also induced locally at the site of a developing response, confers immune accessory function on these cells and may serve to augment and sustain a T cell response.

Human dermal fibroblasts present tetanus toxoid antigen to antigen-specific T cell clones.

Cultured human dermal fibroblasts treated with immune interferon express HLA-DR antigens. We report here that DR-positive fibroblasts present tetanus toxoid (TT) to autologous TT-specific monoclonal helper T cells vigorously depleted of monocytes by passage over Sephadex G10 columns followed by treatment with the monoclonal antibodies (mAb) OKM1 and Leu M1 plus complement. The extent of T cell proliferation in response to TT presented by DR-positive fibroblasts was similar to that elicited using monocytes as antigen-presenting cells. The proliferative response was TT dependent, antigen specific, depended upon DR expression by fibroblasts, appeared MHC restricted, and was completely blocked by mouse mAb to HLA-DR but not by mAb to HLA-A,B, or DQ. DR-positive fibroblasts pulsed with TT were similarly effective in antigen presentation. In summary, immune interferon-stimulated human dermal fibroblasts can substitute for classical antigen-presenting cells in antigen-specific proliferative responses. Since fibroblasts are a ubiquitous cell type in the body, they may play a significant role in the immunobiology of the host.

Complete Primary Structure of Human Histocompatibility Antigen HLA-B7

Tissue grafts cannot be exchanged successfully in the absence of immuno-suppression, except between syngeneic strains or identical twins. From a biochemical standpoint, each individual of a species carries on the surface of its cells substances now known to be glycoproteins that are recognized by every other individual of that species as foreign. These glycoproteins are the products of a highly polymorphic genetic system, first discovered through mouse-breeding studies. Largely through the efforts of Peter Gorer in England and George Snell in Bar Harbor, a region was identified, called the H-2 region, differences at which are the two major histocompatibility antigens, called H-2K and H-2D, were products of two genetic loci in the H-2 region on the 17th mouse chromosome. Subsequently, a variety of othr loci have been identified that are in some manner involved in graf rejection or acceptance. This region is organized similarly in all species that have been examined and is now called the major histocompatibility complex (MHC).

Chapter 4 Complete Primary Structure of Human Histocompatibility Antigen Hla-B7: Evolutionary and Functional Implications

Publisher Summary This chapter focuses on the complete primary structure of human histocompatibility antigen— HLA-B7. The histocompatibility antigens and immunoglobulins are both probably the descendants of some common ancestral gene, which may have originally coded for a cell-bound defense molecule. The development of animals with circulatory systems and duplication of that gene resulted later in an evolution in the secretion of the product of some of these genes into the circulation—i.e., the immunoglobulins. The product of the other genes remained membrane bound and probably went on to evolve to become the histocompatibility antigens. The histocompatibility antigens also serve a defense function for the organism. In this case, the cell-bound defense mechanism may serve to protect the organism from invasion by closely related cells, perhaps serving in primitive organisms to maintain colonial identity on the sea floor. At a different level, the organization of information within a genome can be approached via the cloning of major histocompatibility complex genes by recombinant DNA techniques.

Recent Insights into the Mechanisms of Vascular Injury

Vascular injury and inflammation are the most important features of a heterogeneous group of disorders commonly referred to as the systemic necrotizing vasculitides.1 Previous studies have established two pathogenetic mechanisms for vasculitis2,3: deposition of circulating immune complexes with subsequent complement activation and inflammation; and interactions between circulating antibodies with blood vessel wall antigens in situ, such as occurs in Goodpasture’s syndrome, in which autoantibodies interact with glomerular and pulmonary capillary basement membranes. These mechanisms, however, cannot account for many forms of inflammatory vasculitis and several additional or alternative pathways have recently been explored. In this chapter we will review three settings of vascular injury which may shed light on the pathogenesis of vasculitis. First, we will examine the role of cytokine-induced activation4 of endothelial cells in causing endothelial and vascular injury and the possible role of these effects in one form of vasculitis—Kawasaki’s disease; second, we will describe the details of vascular injury occurring during transplantation reactions, and how these may be relevant to other forms of vasculitis; and third, we will review recent work associating the presence of antineutrophil cytoplasmic antibodies with certain forms of vasculitis, such as Wegener’s granulomatosis.