Immunization of mice with type II collagen (CII) leads to collagen-induced arthritis (CIA), a model for rheumatoid arthritis. T cell recognition of CII is believed to be a critical step in CIA development. We have analyzed the T cell determinants on CII and the TCR used for their recognition, using twenty-nine T cell hybridomas derived from C3H.Q and DBA/1 mice immunized with rat CII. All hybridomas were specific for the CII(256-270) segment. However, posttranslational modifications (hydroxylation and variable O-linked glycosylation) of the lysine at position 264 generated five T cell determinants that were specifically recognized by different T cell hybridoma subsets. TCR sequencing indicated that each of the five T cell epitopes selected its own TCR repertoire. The physiological relevance of this observation was shown by in vivo antibody-driven depletion of TCR Valpha2-positive T cells, which resulted in an inhibition of the T cell proliferative response in vitro towards the non-modified CII(256-270), but not towards the glycosylated epitope. Most hybridomas (20/29) specifically recognized CII(256-270) glycosylated with a monosaccharide (beta-D-galactopyranose). We conclude that this glycopeptide is immunodominant in CIA and that posttranslational modifications of CII create new T cell determinants that generate a diverse TCR repertoire.

Major histocompatibility complex (MHC) encoded antigens, absent or present at only low levels in normal brain tissue, are induced locally around axotomized motor neurons. We here report that immunoreactivity for the potent MHC-inducing factor, gamma-interferon (IFN-gamma), appears in the cytoplasm of such neurons. Rat facial nerves were interrupted (crushed or cut), and later, at various intervals, cryosections from the facial nuclei were subjected to immunohistochemistry with monoclonal antibodies reacting with IFN-gamma and MHC antigens. IFN-gamma-like immunoreactivity appeared briskly in the cytoplasm of the axotomized motor neurons. The immunoreactivity subsided after a nerve crush as the target muscles were reinnervated, but persisted when nerve regeneration was prevented after a nerve cut. These results point to a role for nerve cell-derived IFN-gamma-like molecules in eliciting the neural cell responses to axotomy.

Ventral root avulsion in the rat leads to a retrograde response, with activation of glia and up-regulation of immunologic cell surface molecules such as major histocompatibility complex (MHC) antigens, and the subsequent degeneration of a large proportion of the lesioned motoneurons. Herein, we examined several inbred congenic rat strains previously known to react differently to experimentally induced autoimmune diseases and demonstrate a substantial genetic diversity in the regulation of glial activation and neuron death in this injury model. The panel of examined inbred rat strains included DA(RT1AV1), PVG.1AV1, LEW.1AV1, LEW.1N, BN(RT1N) and E3(RT1U), and the following parameters were determined: (1) MHC class II expression on glia; (2) expression of glial fibrillary acidic protein, C3 complement, and microglial response factor-1 mRNAs in glia; (3) levels of the tumor necrosis factor-alpha and interleukin-1beta cytokine mRNAs; (4) degree of motoneuron loss. The findings of considerable strain-dependent differences in all parameters studied demonstrate important polymorphisms in the genetic regulation of these events. Furthermore, some of the studied features segregated from each other, suggesting independent regulatory mechanisms. Genes outside of the MHC complex are mainly implicated as being of importance for the phenotypic differences, as significant differences were recorded between the MHC congenic strains differing in the non-MHC genes but not vice versa. These results contribute new important insights into the genetic regulation of glial reactivity and neuron death after mechanical nerve injuries. In addition, the finding of conspicuous strain-dependent differences makes it necessary to consider the genetic background when designing and interpreting animal experiments involving noxious insults to the central nervous system resulting in glial activation and nerve cell loss.

The human plasma protein alpha1-microglobulin (alpha1m) was found to inhibit the antigen-induced interleukin-2 (IL-2) production of two different mouse T-helper cell hybridomas. Alpha1m isolated from human plasma and recombinant alpha1m isolated from baculovirus-infected insect cell cultures had similar inhibitory effects. Flow cytometric analysis showed a binding of plasma and recombinant alpha1m to the T-cell hybridomas as well as to a human T-cell line. Radiolabelled plasma and recombinant alpha1m bound to the T-cell hybridomas in a saturable manner and the binding could be eliminated by trypsination of the cells. The affinity constants for the cell binding were calculated to be 0.4-1 x 10(5) M(-1) using Scatchard plotting, and the number of binding sites per cell was estimated to be 5 x 10(5)-1 x 10(6). The cell-surface proteins of one of the T-cell hybridomas were radiolabelled, the cells lysed and alpha1m-binding proteins isolated by affinity chromatography. SDS-PAGE and autoradiography analysis of the eluate revealed major bands with Mr-values around 70, 35 and 15 kDa. The results thus suggest that alpha1m binds to a specific receptor on T cells and that the binding leads to inhibition of antigen-stimulated IL-2 production by T-helper cells.

Allogeneic retinal transplants seem to grow and thrive just as well as syngeneic transplants, but in the former there is considerable upregulation of MHC expression. Our interpretation of these results is that the allogeneic transplants are recognized as nonself, but that there is also something that modifies this reaction of the immune system at this level, preventing the rejection that would normally ensue.

Background and ObjectiveAnti citrullinated protein antibodies (ACPA) are highly specific for rheumatoid arthritis (RA), but the diagnostic accuracy of ACPA in the general population has not been thoroughly assessed. We aimed to assess the diagnostic accuracy of ACPAfor RA in the general population and to further characterise the ACPA repertoires.Material and MethodsSerum samples from alarge population-representative twin cohort consisting of 12,590 individuals were analyzedfor the presence of ACPA using anti-CCP2 ELISA. All ACPA-positive samples (n = 350) were further tested on ELISAs for four peptide-specific ACPAs (alpha-enolase: aa5–21; collagen type II: aa359–369; fibrinogen: aa563–583 and vimentin: aa60–75). RA cases were identified by linkage to the Swedish National Patient Register at inclusion and after a median follow up of 37 months (IQR 31–49).ResultsThree hundred fifty out of 12590 individuals had a positive anti-CCP2 test, measuring ACPA. Of these, 103 had an RA diagnosis at the time of blood donation and inclusion. During a median follow-up of 3 years, an additional 21 of the remaining 247 ACPA-positive individuals developed RA. Overall, anti-CCP2 test and high titers (>3x cut off) of anti-CCP2had sensitivity of 66%and 62% respectively (specificity of 98% and 99% respectively) for prevalent RA. Anti-CCP2 test had a positive predictive value of 29% for prevalent RA at inclusion (negative predictive value of 99.6%) in this population-representative cohort. High titers (>3x cut off) of anti-CCP2 increased the positive predictive value to 48% (negative predictive value of 99.5%). ACPA-positive individuals without RA had lower anti-CCP2 titers and fewer peptide-specific ACPAs than ACPA-positive patients with RA, and higher C-reactive protein levels than anti-CCP2-negative individuals without RA.ConclusionsPresence of ACPA and especially high titers of anti-CCP2 have a high diagnostic accuracy for an RA diagnosis in a population setting.

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