Characterization of blood mononuclear cells of rheumatoid arthritis patients. II. Depressed PPD presentation by monocytes to T lymphocytes

Functional deficiency of antigen-presenting cells in the synovial fluid of rheumatoid arthritis

In our study of rheumatoid arthritis (RA) patients, we observed a decrease of tetanus toxoid antigen-presenting capacity of synovial fluid (SF) adherent cells to autologous T cells of either SF or peripheral blood. Additionally, we found a higher capacity of adherent synovial cells to stimulate autologous T-lymphocytes. Our results suggest that antigen-presenting cells of the SF of RA patients have defects that may play a role in defective presentation of antigens in joints and may account for other abnormal functions important in the pathogenesis of RA.

Activation of macrophages in an experimental rat model of arthritis induced by Erysipelothrix rhusiopathiae infection

Infection of Lewis rats with Erysipelothrix rhusiopathiae represents an experimental model system of acute and chronic arthritis. We studied here the acute inflammatory phase with respect to stimulation of macrophages and lymphocytes. Intragluteal injection of viable E. rhusiopathiae (10(2) to 10(4) bacteria) rapidly induced generalized inflammation, loss of body weight, hind leg arthritis, and systemic macrophage activation within 2 to 3 days. The same symptoms could also be evoked by injection of dead E. rhusiopathiae. Ex vivo, peritoneal macrophages released large amounts of tumor necrosis factor alpha on day 2 and interleukin-1 on day 3, whereas production of prostaglandin E2 was delayed to days 5 to 7 and appeared to counteract tumor necrosis factor alpha synthesis. The inflammatory response and development of arthritis were strongly dependent on T lymphocytes, as evidenced by the following findings: (i) lymphocytes released lymphokines that activated macrophages to enhanced mediator release; (ii) treatment of rats with cyclosporin A reduced infection-induced macrophage activation; (iii) mitogen-stimulated thymocyte proliferation was enhanced, indicating an infection-induced maturation-differentiation process in the thymus; and (iv) in T-cell-deficient nude rats, a higher dose of bacteria was required for infection, the inflammatory response was less severe, and only mild, but not chronic, arthritis developed. Thus, an E. rhusiopathiae-induced inflammation in rats provides a useful tool to characterize activated macrophages and T lymphocytes during the development of acute arthritis and its transition into the chronic form.

Depressed PPD and tetanus toxoid presentation by monocytes to T lymphocytes in patients with rheumatoid arthritis: restoration by interferon gamma

A diminished antigen presentation of blood monocytes to autologous T cells has been recently described in patients with rheumatoid arthritis (RA). In this study the defective presentation of common recall antigens by blood monocytes revealed it to be a monocyte dysfunction specific for RA which could not be found in other chronic inflammatory rheumatic or non-rheumatic diseases and which could be restored by recombinant human interferon gamma. In addition, RA monocytes in blood exhibited a strongly reduced expression of HLA-DR determinants on the cell surface. T cells from RA patients produced almost normal interleukin-2 (IL-2) levels and showed a normal IL-2 sensitivity after phytohemagglutinin (PHA) stimulation. Several reasons may be responsible for this altered monocyte function in RA. Among these an in vivo "preactivation" of monocytes associated with a reduced antigen-presenting capacity or an impaired regulation of monocyte/macrophage differentiation are discussed.

Macrophage migration and maturation within rheumatoid nodules

In long-established rheumatoid nodules, monocytes continue to be recruited and to migrate from the outer vascular zone toward the palisade and central necrotic area. Maturation of these cells is shown to take place during tissue migration. We found that the great majority of palisade cells express exclusive mononuclear phagocyte phenotypes. Among this mononuclear phagocyte population are many cells that bear the receptor for iC3b (CR3), but few that bear the receptor for C3b (CR1). HLA-D region molecule expression is intense and widespread.

Reduced production of interferon alpha and interferon gamma in leukocyte cultures from patients with active rheumatoid arthritis

Tests for lymphoproliferation and interferon induction in normal blood donors and patients with rheumatoid arthritis (RA) were performed in a whole-blood assay. Patients with high inflammatory RA showed significantly reduced lymphoproliferation and interferon gamma production after stimulation with phytohemagglutinin (PHA) and concanavalin A (Con A) when compared with patients with low inflammatory activity, or with normal control individuals. Similarly, patients with high and low inflammatory RA exhibited a significantly reduced interferon alpha production after stimulation with Newcastle Disease Virus (NDV) when compared with normal blood donors. Our findings may point to an important immunodeficiency of the circulating lymphocytes of RA patients and may explain some of the in vitro immunoregulatory abnormalities reported in this disease.

Effect of polymeric IgG on human accessory cell function

Circulating immune complexes are considered to have a profound effect on host defense mechanisms against invading pathogens and to modulate cellular interactions required for an appropriate course of the immune response. In this study we have investigated the influence of polymeric IgG (used as a model system for immune complexes) on accessory functions of human monocytes. We show that a short (1 hr) incubation of human monocytes in the presence of polymeric IgG (16 hr prior to antigen pulsing) led to a significant decrease of these cells' antigen-presenting capacity while accessory functions in alloantigen- or mitogen-driven proliferation systems remained unimpaired. The polymeric IgG-induced impairment of antigen presentation, which was assessed by diminished proliferation of antigen-reactive T cells following stimulation by antigen-pulsed polymeric IgG-treated or Dulbecco's phosphate-buffered saline (PBS-D)-treated control monocytes, could not be attributed to the generation of suppressor mechanisms (no release of soluble suppressor factors, no induction of suppressive monocytes). The release of interleukin-1 by polymeric IgG-treated monocytes and PBS-D-treated monocytes was comparable and polymeric IgG did not down modulate major histocompatibility complex (MHC) class II molecules already expressed in the monocyte plasma membrane. Profound changes in the monocyte plasma membrane occurring subsequent to polymeric IgG treatment possibly accompanied by altered kinetics of MHC class II reexpression are likely to contribute to the observed decrease of antigen presentation.

Enhanced prostanoid release from monocytes of patients with rheumatoid arthritis and active systemic lupus erythematosus

In patients with rheumatoid arthritis high levels of prostaglandin E1 have been found in the joint fluid, and its increased production by adherent synovial cells and macrophages clearly supports the notion that this arachidonic acid metabolite is involved in the pathology of the disease. Besides its known inflammatory qualities and the suppressive effects on various lymphocyte functions prostaglandin E2 has proved to be an essential cofactor in the secretion of the lymphokine osteoclast activating factor. In this study we have discovered an enhanced release of prostaglandin E1 and thromboxane B2 from a subpopulation of blood monocytes from patients with rheumatoid arthritis and active systemic lupus erythematosus. No correlation between prostanoid release from monocytes and inflammatory activity of the disease was found. However, even monocytes from patients with early stage or mild inflammatory activity displayed a 'stimulated' arachidonic acid metabolism. In contrast only patients with active systemic lupus erythematosus showed in this respect comparable secretory activity or monocytes. Our findings may point to a possible pathogenic role of prostanoids in rheumatoid arthritis, which may also have some implication for the early diagnosis of this disease and for its differentiation from other chronic inflammatory rheumatic conditions.

Immune system in rheumatoid arthritis: possible implications in neoplasms

Although the immune system in rheumatoid arthritis is generally in a state of hyperactivity, deficient function can be demonstrated in certain specific parts of the system. This has been most clearly demonstrated in studies of the response of blood lymphocytes from demonstrated in studies of the response of blood lymphocytes from patients with rheumatoid arthritis to in vitro infection by the Epstein-Barr virus. The virus normally infects B cells promoting proliferation. This results in the establishment of permanent lines of infected B cells more commonly than normal in rheumatoid arthritis. This condition is associated with decreased production of lymphokines, interleukin-2, and gamma interferon. Similar in vitro problems in immune responses to other antigens have also been described. Although natural killer cells are scarce among synovial cells, they are present in normal numbers in the blood. Whether these select immunodeficiencies make patients with rheumatoid arthritis more prone to neoplasms, particularly lymphomas, is a question that has not been investigated until now. Nor has it been determined whether the immune abnormalities in rheumatoid arthritis make patients more prone to neoplasms from the therapeutic agents used in their treatment.