For advanced progressive primary IgA nephropathy (IgAN) no established therapy exists. We conducted a prospective, uncontrolled trial to evaluate the effect of intravenous cyclophosphamide pulse (CyP) therapy on the course of advanced progressive IgAN. Twenty-one patients (mean age 52 ± 10 years; male/female 20/1) with biopsy-proven IgAN without crescentic extracapillary proliferation and a serum creatinine of more than 2.0 mg/dl and/or an increase more than 25% in the previous 3 months were included. Patients were treated with CyP (750 mg/m² body surface area) every 4 weeks for 6 months and low dose oral prednisolone. The loss of renal function per year was significantly reduced from 16% before therapy to 4% after therapy (p < 0.001). A further increase >25% of serum creatinine after therapy was observed in 8 patients after 0.7 years (range 0.3–3.0 years), and 3 of these patients developed end-stage renal disease. Proteinuria decreased significantly during CyP therapy. A low nadir of white blood cell and platelet count was associated with a better renal outcome (p = 0.025). In conclusion, CyP therapy and low dose oral prednisolone is effective in preserving renal function in a subgroup of patients with advanced progressive IgAN.

Yersinia heat-shock protein 60 (Ye-hsp60) has recently been found to be a dominant CD4 and CD8 T cell Ag in Yersinia-triggered reactive arthritis. The nature of this response with respect to the epitopes recognized and functional characteristics of the T cells is largely unknown. CD4+ T cell clones specific for Ye-hsp60 were raised from synovial fluid mononuclear cells from a patient with Yersinia-triggered reactive arthritis. and their specificity was determined using three recombinant Ye-hsp60 fragments, overlapping 18-mer synthetic peptides as well as truncated peptides. Functional characteristics were assessed by cytokine secretion analysis in culture supernatants after specific antigenic stimulation. Amino acid positions relevant for T cell activation were detected by single alanine substitutions within the epitopes. Fragment II comprising amino acid sequence 182–371 was recognized by the majority of clones. All these clones were specific for peptide 319–342. Th1 clones and IL-10-secreting clones occurred in parallel, sometimes with the same fine specificity. The 12-mer core epitope 322–333 is a degenerate MHC binder and is presented to some T cell clones in a “promiscuous” manner. This epitope is almost identical with a B27-restricted CTL epitope of Ye-hsp60. Cross-reactivity of Ye-hsp60-specific T cell clones with self-hsp60 was not observed. In conclusion, an interesting Ye-hsp60 T cell epitope has been identified and characterized. It remains to be determined whether this epitope is also relevant in other reactive arthritis patients.

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Cationic antigens are known to have considerable arthritogenic potential in experimental systems. During a systematic search for suitable, naturally occurring candidates an intracellular protein was isolated from the ribosomal pellet of Yersinia enterocolitica 0:3, a bacterial strain associated with reactive arthritis in humans. The protein is highly cationic, contains two 19-kD polypeptide chains linked by a disulfide bond, and reveals a strong tendency for spontaneous aggregation. It is suggested to be a nucleic acid binding protein. We tested this antigen for its ability to induce arthritis after intra-articular challenge in preimmunized rats. An acute inflammatory phase followed by transition to chronicity was observed both by technetium-99m scintigraphy and from histology. Massive polymorphonuclear leucocyte infiltration of the synovium was seen early on and fibrosis and thickening of the joint capsule occurred in later stages. Control groups showed no evidence of inflammation. Western blot and ELISA analysis of unselected sera from Yersinia enterocolitica 0:3-infected patients revealed antibodies to the antigen in the majority of cases, whereas healthy individuals rarely reacted. This is the first report of a naturally occurring cationic antigen capable of inducing immunologic tissue injury; it justifies the speculation that cationic antigens from prokaryotic cells could trigger reactive arthritis.in humans. (J. Clin. Invest. 1991. 87:632-642.)