Simple developmental programs of gene expression and cellular composition of lymphoid organs at the origin of natural tolerance

Natural autoantibodies against glomerular basement membrane exist in normal human sera

Autoimmunity to glomerular basement membrane (GBM) could induce Goodpasture disease, and natural autoantibodies against GBM in the sera of normal individuals were not reported. The aim of the study was to identify and characterize natural autoantibodies against GBM in normal human sera. Natural anti-GBM autoantibodies were purified from the sera of five healthy persons by affinity chromatography, using purified bovine alpha(IV)non-collagenous (NC1) as solid-phase ligands. Antigen specificity, immunoglobulin G (IgG) subclasses, and antibody avidity of the natural autoantibodies were investigated by enzyme-linked immunosorbant assay (ELISA), Western-blot analysis, indirect immunofluorescence, and antigen-inhibition ELISA, and compared with those of 32 patients with anti-GBM disease. Natural anti-GBM autoantibodies could be purified from IgG fractions of all the five persons, with an average amount of 0.5% of total IgG fractions. Antigen specificity of the natural autoantibodies was identified by blotting to human alpha(IV)NC1, reactivity to recombinant alpha3(IV)NC1, and linear staining along the GBM of normal kidney sections. Titers of the natural autoantibodies were much lower than those of patients (1:60.6 vs 1:993.6, P<0.001). IgG subclasses distribution of the natural autoantibodies was restricted to IgG2 (100%) and IgG4 (100%), while for patients it was mainly IgG1 (93.8%) and IgG4 (90.6%). Avidity of the natural autoantibodies was lower than that of patients, the amount of alpha(IV)NC1 used for 50% inhibition was 1.65 and 0.46 microg, respectively (P<0.05). In conclusion, natural anti-GBM autoantibodies exist in normal human sera. Antibody levels, IgG subclasses, and avidity of the natural autoantibodies were different from those of patients. Fine specificity of the natural autoantibodies needed to be elucidated.

General network of natural autoantibodies as immunological homunculus (Immunculus)

The term 'Immunculus' has been proposed for designation of the global system (network) of constitutively expressed natural autoantibodies (na-Ab) interacting specifically with different extracellular, membrane, cytoplasmic, and nuclear self-antigens. In healthy persons the repertoires of such na-Ab are surprisingly constant and characterized by minimal individual quantitative variations. On the other hand, abnormal metabolic deviations, which precede or accompany different diseases show easily detectable prominent changes, rather quantitative than qualitative, in the network of na-Ab in the patient's sera (Immunculus distortions). This phenomenon can be used for 'mapping' the state of physiological norm in terms of the millennia of na-Ab repertoires, and for the elaboration of methods for an early (pre-clinical) detection of potentially pathogenic metabolic changes. Can the individual features of the general network of constitutively expressed na-Ab reflect the functional state of the body and be used for 'mapping' of normal and pathological functional state? Can the changes in production of some biologically active na-Ab not only reflect the state of the body, but also be used for partial compensation of functional deficiency of certain molecular systems? These and related questions are discussed in this article. The research project 'Immunculus' is proposed for international cooperative investigations.

Mice expressing the E7 oncogene of HPV16 in epithelium show central tolerance, and evidence of peripheral anergising tolerance, to E7-encoded cytotoxic T-lymphocyte epitopes

In order to derive mice which expressed both the E7 open reading frame transgene of human papillomavirus type 16 in skin and MHC class 1 restriction elements for several E7-encoded cytotoxic T-lymphocyte (CTL) epitopes, K14.HPV16E7 mice which express E7 in basal keratinocytes were crossed to the F1 generation with A2.1 Kb transgenic mice which express the MHC binding cleft domains of human HLA A*0201, and murine H-2b. F1 mice (denoted K14E7 x A2.1) expressed E7 in the thymus at least as early as 2-5 days before birth. Immunisation of FVB x A2.1 control mice (transgenic for HLA A*0201 and H-2b but not for E7), with two HLA A*0201-restricted epitopes of E7 and one H-2b-restricted CTL epitope of E7, gave strong primary CTL responses recognising epitope-pulsed or constitutively E7-expressing syngeneic target cells. In contrast, in immunised K14E7 x A2.1 mice, the CTL responses to the H-2b epitope and one of the HLA A*0201 CTL epitopes were strongly down-regulated, and to the other HLA A*0201 epitope, completely abolished, as demonstrated by percentage specific killing by bulk splenocyte cultures in cytotoxicity assays, and by CTL precursor frequency analysis. In thymus-transplanted bone marrow radiation chimeras in which the immune system of K14E7 x A2.1 mice was replaced by a FVB x A2.1 immune system, specific immunisation did not result in reemergence of strong E7-directed CTL responses. In agreement with these in vitro findings, specific immunisation failed to significantly alter the course of E7-associated tumour development in K14E7 x A2.1 mice. These data are consistent with a model of central deletional CTL tolerance to E7-encoded epitopes recognised in the context of two distinct MHC class 1 restriction elements, and with the possibility of peripheral T-cell anergy maintained by expression of E7 in the skin.