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Objective. To investigate the effect of CD25+ or CTLA-4+ cell depletion on the natural history of collagen-induced and spontaneous arthritis in male DBA1/J mice.Methods. Male DBA/1J mice were treated with anti-CD25 depleting antibody (PC61) or isotype control (GL113), or with anti-CTLA-4 depleting antibody (4F10) at various time-points peri- and post-immunization with bovine collagen type II, emulsified in adjuvant. In order to develop a model system in which long-term depletion of CD25+ regulatory T cells can be achieved prior to immunization, adult male DBA/1J mice were thymectomized prior to administration of either PC61 or GL113. An ELISA demonstrated that PC61 and GL113 antibodies were undetectable by 21 days after administration and FACS analysis confirmed the long-term depletion of CD25+ cells in peripheral blood.Results. In the thymectomized mice treated with PC61, the CD25+ population was depleted and a spontaneous arthritis developed (P = 0.03). In the non-thymectomized mice, administration of CTLA-4-depleting antibody prior to immunization exacerbated arthritis in mice immunized with bovine collagen type II emulsified in incomplete Freund's adjuvant (P<0.01). However, no significant difference in the natural history of arthritis was evident in mice treated with CD25-depleting antibody (PC61) compared with control antibody (GL113).Conclusions. Two separate models implicate CD25+ CTLA-4+ constitutive cells in suppression of arthritis in susceptible DBA/1 males: exacerbation of collagen-induced arthritis following CTLA-4 depletion at the start of induction and spontaneous arthritis in the thymectomy/CD25+ depletion model.

Objectives. In addition to its vasoactive effects, angiotensin II has proinflammatory properties. Angiotensin-converting enzyme (ACE) inhibitors reduce the production of angiotensin II and could therefore act as anti-inflammatory agents. Here we investigated the capacity of the ACE inhibitor quinapril to modulate inflammatory arthritis.Methods. We studied the effect of quinapril on disease activity in mice with collagen-induced arthritis (CIA). Mice received oral quinapril (10 mg/kg/day) at the time of arthritis induction (prophylaxis protocol) or at the onset of mild arthritis (therapy protocol). Concentrations of immunoglobulin G (IgG) subtypes specific for bovine Type II collagen and TNF-α were measured by enzyme-linked immunoassay.Results. Quinapril significantly diminished the activity of CIA when given as prophylaxis or therapy (prophylaxis protocol, P<0.001; therapy protocol P = 0.002). Antigen-specific IgG2a antibodies were reduced by 52% (P = 0.02) in the quinapril prophylaxis protocol. Suppression of arthritis by quinapril was associated with reduced articular expression of TNF-α by 68% (P = 0.01) in the prophylaxis protocol and 27% (P = 0.06) in the therapy protocol. Quinapril therapy also inhibited expression of splenocyte TNF-α production following lipopolysaccharide (LPS) in vitro stimulation by 59% (P = 0.02). In parallel human in vitro experiments, ACE inhibition suppressed LPS-stimulated production of TNF-α by monocytes. In order to confirm that the action of quinapril occurred predominantly through suppression of angiotensin II, parallel experiments with the angiotensin receptor antagonist candesartan cilexetil demonstrated that this agent also inhibited disease activity in CIA.Conclusions. These data suggest that angiotensin II is a mediator of chronic inflammation and that ACE inhibition may have therapeutic effects in human inflammatory arthritis.

Inflammation caused by inoculation of Mycoplasma gallisepticum (MG) into the air sacs was compared in chickens previously exposed by intramuscular injection of MG with that produced in nonimmunised chickens. Air sacs from chickens inoculated with Frey's media, from those receiving only intramuscular injections of MG, and from nonimmunised non-challenged birds were included in the evaluations. The airsacculitis produced in immunised chickens was more severe at 48 hours post-challenge infection than that produced in nonimmune chickens. At 96 hours after challenge, the airsacculitis in nonimmunised chickens was significantly more severe than that produced in chickens of any other experimental group.The protective effect of immunisation at 96 hours was demonstrated clearly by using the techniques of ring-stabilisation for collection, processing, and embedding of air sacs and microcomputer-assisted morpho-metric analysis. Air sac wall thickness and area measurements correlated positively with subjective impressions on the degree of airsacculitis and with determinations made by point count analysis of the relative percentage of selected components of inflammation.

It has recently become clear that the minor lymphocyte stimulatory antigens (Mls) and other endogenous ligands which lead to the partial or total deletion of T cells bearing particular Vβ segments are encoded by mouse mammary tumor virus (MMTV). We review here the genetic analyses of multiple Vβ11 and Vβ3 deletion ligands and demonstrate the involvement of MMTV in all examples. Several features of Mls and the Vβ11/Vβ3 deleting ligands identify them as members of the superantigen family. Bacterial superantigens are known to bind both MHC class II and the TCR in regions distinct from conventional peptide antigens. Within the MMTV genome, the 3' LTR has been identified as encoding superantigen function. We present data demonstrating that in vitro translation identifies the major product of the open reading frame (ORF) within the 3' LTR as a type II integral membrane glycoprotein. It is proposed that the type II membrane glycoprotein interacts with MHC and TCR in a manner analogous to the bacterial superantigens and distinct from conventional peptide antigen. Several unanswered questions regarding superantigen action remain; what determines total or partial deletion? How is Mls transferred between cells? These questions are addressed in the discussion.

The activity of T lymphocyte precursors (pre-T cells) in the bone marrow of mice was measured by the concanavalin A response synergy assay. Pre-T cell levels were low in marrow of neonatally thymectomized mice and could be restored to control values by treatment in vivo with an extract of mouse thymus. Levels of activity were also low in aging mice and again could be restored by thymic extract treatment. The most profound fall with aging was in the proliferating pre-T cell compartment as detected by tritiated thymidine suicide; and this compartment was restored by thymic extract treatment. Irradiation to the thymus, with the bone marrow shielded, caused a fall in resting pre-T cells in the bone marrow and a concomitant rise in proliferating cells. These results are consistent with a model of control of pre-T cell maturation in which the thymus senses the number of developing lymphocytes within it and responds to a fall in this number by increasing production of hormone. The hormone acts on resting pre-T cells in the marrow, stimulating some of them to proliferate, leave the bone marrow, and repopulate the thymus.

When mouse bone marrow cells are mixed with cortisol-resistant thymocytes and stimulated in vitro with concanavalin A, the mitogenic response observed is much greater than additive, that is, it is synergistic. Between 94 and 96% of responding cells could be identified as T cells (Thy-1 positive) and of these, 79-100% derived from the cortisol-resistant thymocyte population, not from the bone marrow. Purified macrophages could not replace bone marrow; and marrow depleted of mature T or B cells worked as well as normal marrow. Thus, T and B cells and macrophages were ruled out as the synergizing cell of bone marrow. Nude spleen contained 10 times as many precursors of T cells as did nude marrow and was 10 times better at synergy with cortisol-resistant thymocytes. This implication of the pre-T cell as synergizer was supported by the finding that the synergistic activity of marrow was lost on preincubation, but maintained if the preincubation medium contained thymosin or cyclic AMP. Thus, the ability to enhance the response of relatively mature T cells to Con A is a property of pre-T cells. It is anticipated that this property will allow more detailed studies of T-cell precursor development in mice, and possibly in man.