Antiribosomal antibodies in SLE, infection, and following deliberate immunization

Characterization of anti-P monoclonal antibodies directed against the ribosomal protein-RNA complex antigen and produced using Murphy Roths large autoimmune-prone mice

Autoantibodies, including anti-ribosomal P proteins (anti-P), are thought to be produced by an antigen-driven immune response in systemic lupus erythematosus (SLE). To test this hypothesis, we reconstituted the ribosomal antigenic complex in vitro using human P0, phosphorylated P1 and P2 and a 28S rRNA fragment covering the P0 binding site, and immunized Murphy Roths large (MRL)/lrp lupus mice with this complex without any added adjuvant to generate anti-P antibodies. Using hybridoma technology, we subsequently obtained 34 clones, each producing an anti-P monoclonal antibody (mAb) that recognized the conserved C-terminal tail sequence common to all three P proteins. We also obtained two P0-specific monoclonal antibodies, but no antibody specific to P1, P2 or rRNA fragment. Two types of mAbs were found among these anti-P antibodies: one type (e.g. 9D5) reacted more strongly with the phosphorylated P1 and P2 than that with their non-phosphorylated forms, whereas the other type (e.g. 4H11) reacted equally with both phosphorylated and non-phosphorylated forms of P1/P2. Both 9D5 and 4H11 inhibited the ribosome/eukaryotic elongation factor-2 (eEF-2)-coupled guanosine triphosphate (GTP)ase activity. However, preincubation with a synthetic peptide corresponding to the C-terminal sequence common to all three P proteins, but not the peptide that lacked the last three C-terminal amino acids, mostly prevented the mAb-induced inhibition of GTPase activity. Thus, at least two types of anti-P were produced preferentially following the immunization of MRL mice with the reconstituted antigenic complex. Presence of multiple copies of the C-termini, particularly that of the last three C-terminal amino acid residues, in the antigenic complex appears to contribute to the immunogenic stimulus.

Ribosomal versus non-ribosomal cellular antigens: factors determining efficiency of indirect presentation to CD4+ T cells

Proteins released from dying cells can be taken up and presented by antigen-presenting cells (APC) to T cells. While the presentation of such self antigens may lead to beneficial anti-tumour responses, in autoimmune disease it leads to pathological immune responses. The sub-set of self proteins targeted in autoimmune disease is circumscribed, and certain cellular components such as ribonucleoprotein (RNP) complexes are often targeted. Although explanations for this antigen selectivity have been proposed, there has been little direct testing of these hypotheses. We and others previously showed that ribosomal proteins, targeted in autoimmune disease, are also targets of anti-tumour T-cell responses. We asked whether particular properties of ribosomal proteins such as incorporation into RNP complexes or sub-cellular localization enhance ribosomal protein presentation by APC to CD4(+) T cells. Ribosomal protein antigens within purified intact ribosomes or free of the ribosomes were equally well taken up and presented by APC, demonstrating that inclusion of ribosomal proteins into an RNP complex does not confer an advantage. However, antigens localized to ribosomes within apoptotic cells were less efficiently taken up and presented by APC than the same antigens localized diffusely throughout the cell. This suggests that presentation of ribosomal proteins is somehow down-regulated, possibly to facilitate presentation of other less-abundant intracellular proteins. Consequently, the explanation for the frequent targeting of ribosomal proteins by both autoimmune and anti-tumour T-cell responses is not at the level of uptake from apoptotic cells and must be sought elsewhere.

Clinical and biological aspects of anti-P-ribosomal protein autoantibodies

Among the many clinical manifestations of systemic lupus erythematosus (SLE), central nervous system (CNS) involvement is of a prognostic importance. In this respect, anti-ribosomal P protein antibodies were shown by many to occur in association with SLE neuropsychiatric manifestations, mainly psychosis. The prevalence of anti-P antibodies was strongly related to disease activity wherein disease remission was associated with the disappearance of these antibodies. In addition to its association with CNS involvement, the occurrence of liver and kidney disease in SLE patients with anti-P antibodies was widely reported. Anti-P antibodies are able to bind T cells, monocytes, neurons and hepatocytes thereby enhancing the production of pro-inflammatory cytokines and both CNS and liver damage. Similar to the ability of anti-dsDNA antibodies, anti-P antibodies were shown to penetrate into living cells, leading to cell dysfunctions such as cell apoptosis. These biological aspects may play an important role in the pathogenesis of SLE.

Is it SLE?

Systemic lupus erythematosus (SLE) is a chronic inflammatory autoimmune disease, as yet of unknown aetiology, with diverse clinical manifestations and a variable course and prognosis. The diagnosis is based on recognizing the overall pattern of clinical and laboratory abnormalities. However, even today, there is often a significant delay between onset of symptoms and diagnosis. Over the last two decades there has been great progress in identifying the profile of antinuclear antibodies that characterizes SLE, and in this chapter we describe how serological techniques can be important tools for the clinician in the early diagnosis of this disorder. Also described is the lupus band test, which has rather fallen out of favour as a diagnostic tool but which can still provide valuable evidence for the diagnosis in patients in whom the clinical and serological features are inconclusive. Nevertheless, because the presentation of lupus is protean, and the early manifestations are often non-specific, SLE can still be easily confused with a wide range of other conditions. Here, we describe some of the common clinical conundrums encountered in patients referred to the Lupus Clinic to 'rule out lupus', providing a framework for diagnosis. Finally, the chapter considers the major problem that clinicians who treat patients with SLE frequently face in distinguishing between a flare of lupus and infection. Diagnosis of SLE is still a great clinical challenge, and while it is important to recognize patients with potentially aggressive disease and treat them appropriately at an early stage it is also important to be able to recognize patients with potentially benign disease and avoid over-treatment.

Can immunization precipitate connective tissue disease? Report of five cases of systemic lupus erythematosus and review of the literature

OBJECTIVES

To report a series of five patients who developed systemic lupus erythematosus (SLE) after immunization and review the literature on vaccine-associated connective tissue diseases and the theoretical mechanisms that could explain such an association.

METHODS

Uncontrolled retrospective analysis of cases identified sporadically over 7 years at three centers.

RESULTS

In our series of 5 patients, symptoms of SLE developed within 2 to 3 weeks after secondary immunization. All patients met American College of Rheumatology (ACR) criteria for the diagnosis of SLE. In most patients, symptoms have been persistent.

CONCLUSION

Although a coincidental association between vaccination and the onset of SLE cannot be excluded, the temporal relationship with the development of symptoms makes it immunologically plausible that vaccination triggered systemic autoimmunity in these rare cases. We propose that epidemiological studies be performed to examine this potential association in more detail to quantitate the risk and identify possible genetic risk factors.