MicroRNAs modulate immunological and inflammatory responses in Holstein cattle naturally infected with Mycobacterium avium subsp. paratuberculosis

MicroRNAs (miRNAs) regulate the post-transcriptional expression of genes by binding to their target mRNAs. In this study, whole miRNA sequencing was used to compare the expression of miRNAs in ileocecal valve (ICV) and peripheral blood (PB) samples of cows with focal or diffuse paratuberculosis (PTB)-associated lesions in gut tissues versus (vs) control cows without lesions. Among the eight miRNAs differentially expressed in the PB samples from cows with diffuse lesions vs controls, three (miR-19a, miR-144, miR32) were also down-regulated in cows with diffuse vs focal lesions. In the ICV samples, we identified a total of 4, 5, and 18 miRNAs differentially expressed in cows with focal lesions vs controls, diffuse lesions vs controls, and diffuse vs focal lesions, respectively. The differential expression of five microRNAs (miR-19a, miR-144, miR-2425-3p, miR-139, miR-101) was confirmed by RT-qPCR. Next, mRNA target prediction was performed for each differentially expressed miRNA. A functional analysis using the predicted gene targets revealed a significant enrichment of the RNA polymerase and MAPK signaling pathways in the comparison of cows with focal vs no lesions and with diffuse vs focal lesions, respectively. The identified miRNAs could be used for the development of novel diagnostic and therapeutical tools for PTB control.

Multi-omics Characterization of Response to PD-1 Inhibitors in Advanced Melanoma

Immunotherapy improves the survival of patients with advanced melanoma, 40% of whom become long-term responders. However, not all patients respond to immunotherapy. Further knowledge of the processes involved in the response and resistance to immunotherapy is still needed. In this study, clinical paraffin samples from fifty-two advanced melanoma patients treated with anti-PD-1 inhibitors were assessed via high-throughput proteomics and RNA-seq. The obtained proteomics and transcriptomics data were analyzed using multi-omics network analyses based on probabilistic graphical models to identify those biological processes involved in the response to immunotherapy. Additionally, proteins related to overall survival were studied. The activity of the node formed by the proteins involved in protein processing in the endoplasmic reticulum and antigen presentation machinery was higher in responders compared to non-responders; the activity of the immune and inflammatory response node was also higher in those with complete or partial responses. A predictor for overall survival based on two proteins (AMBP and PDSM5) was defined. In summary, the response to anti-PD-1 therapy in advanced melanoma is related to protein processing in the endoplasmic reticulum, and also to genes involved in the immune and inflammatory responses. Finally, a two-protein predictor can define survival in advanced disease. The molecular characterization of the mechanisms involved in the response and resistance to immunotherapy in melanoma leads the way to establishing therapeutic alternatives for patients who will not respond to this treatment.

Hypoxia classifier for transcriptome datasets

Molecular gene signatures are useful tools to characterize the physiological state of cell populations, but most have developed under a narrow range of conditions and cell types and are often restricted to a set of gene identities. Focusing on the transcriptional response to hypoxia, we aimed to generate widely applicable classifiers sourced from the results of a meta-analysis of 69 differential expression datasets which included 425 individual RNA-seq experiments from 33 different human cell types exposed to different degrees of hypoxia (0.1–5%\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {O}_{2}$$\end{document}O2) for 2–48 h. The resulting decision trees include both gene identities and quantitative boundaries, allowing for easy classification of individual samples without control or normoxic reference. Each tree is composed of 3–5 genes mostly drawn from a small set of just 8 genes (EGLN1, MIR210HG, NDRG1, ANKRD37, TCAF2, PFKFB3, BHLHE40, and MAFF). In spite of their simplicity, these classifiers achieve over 95% accuracy in cross validation and over 80% accuracy when applied to additional challenging datasets. Our results indicate that the classifiers are able to identify hypoxic tumor samples from bulk RNAseq and hypoxic regions within tumor from spatially resolved transcriptomics datasets. Moreover, application of the classifiers to histological sections from normal tissues suggest the presence of a hypoxic gene expression pattern in the kidney cortex not observed in other normoxic organs. Finally, tree classifiers described herein outperform traditional hypoxic gene signatures when compared against a wide range of datasets. This work describes a set of hypoxic gene signatures, structured as simple decision tress, that identify hypoxic samples and regions with high accuracy and can be applied to a broad variety of gene expression datasets and formats.

Vaccine breakthrough infections with SARS-CoV-2 Alpha mirror mutations in Delta Plus, Iota, and Omicron

Replication of SARS-CoV-2 in the human population is defined by distributions of mutants that are present at different frequencies within the infected host and can be detected by ultra-deep sequencing techniques. In this study, we examined the SARS-CoV-2 mutant spectra of amplicons from the spike-coding (S-coding) region of 5 nasopharyngeal isolates derived from patients with vaccine breakthrough. Interestingly, all patients became infected with the Alpha variant, but amino acid substitutions that correspond to the Delta Plus, Iota, and Omicron variants were present in the mutant spectra of the resident virus. Deep sequencing analysis of SARS-CoV-2 from patients with vaccine breakthrough revealed a rich reservoir of mutant types and may also identify tolerated substitutions that can be represented in epidemiologically dominant variants.

miRNA Profile Based on ART Delay in Vertically Infected HIV-1 Youths Is Associated With Inflammatory Biomarkers and Activation and Maturation Immune Levels

Early antiretroviral treatment (ART) in vertically acquired HIV-1-infection is associated with a rapid viral suppression, small HIV-1 reservoir, reduced morbimortality and preserved immune functions. We investigated the miRNA profile from vertically acquired HIV-1-infected young adults based on ART initiation delay and its association with the immune system activation. Using a microRNA panel and multiparametric flow cytometry, miRNome profile obtained from peripheral blood mononuclear cells and its association with adaptive and innate immune components were studied on vertically HIV-1-infected young adults who started ART early (EARLY, 0-53 weeks after birth) and later (LATE, 120-300 weeks). miR-1248 and miR-155-5p, were significantly upregulated in EARLY group compared with LATE group, while miR-501-3p, miR-548d-5p, miR-18a-3p and miR-296-5p were significantly downregulated in EARLY treated group of patients. Strong correlations were obtained between miRNAs levels and soluble biochemical biomarkers and immunological parameters including CD4 T-cell count and maturation by CD69 expression on CD4 T-cells and activation by HLA-DR on CD16^high NK cell subsets for miR-1248 and miR-155-5p. In this preliminary study, a distinct miRNA signature discriminates early treated HIV-1-infected young adults. The role of those miRNAs target genes in the modulation of HIV-1 replication and latency may reveal new host signaling pathways that could be manipulated in antiviral strategies. Correlations between miRNAs levels and inflammatory and immunological markers highlight those miRNAs as potential biomarkers for immune inflammation and activation in HIV-1-infected young adults who initiated a late ART.

Description of the genetic variants identified in a cohort of patients diagnosed with localized anal squamous cell carcinoma and treated with panitumumab

Squamous cell carcinoma is the most frequent histologic type of anal carcinoma. The standard of care since the 1970s has been a combination of 5-fluorouracil, mitomycin C, and radiotherapy. This treatment is very effective in T1/T2 tumors (achieving complete regression in 80–90% of tumors). However, in T3/T4 tumors, the 3-year relapse free survival rate is only 50%. The VITAL trial aimed to assess the efficacy and safety of panitumumab in combination with this standard treatment. In this study, 27 paraffin-embedded samples from the VITAL trial and 18 samples from patients from daily clinical practice were analyzed by whole-exome sequencing and the influence of the presence of genetic variants in the response to panitumumab was studied. Having a moderate- or high-impact genetic variant in PIK3CA seemed to be related to the response to panitumumab. Furthermore, copy number variants in FGFR3, GRB2 and JAK1 were also related to the response to panitumumab. These genetic alterations have also been studied in the cohort of patients from daily clinical practice (not treated with panitumumab) and they did not have a predictive value. Therefore, in this study, a collection of genetic alterations related to the response with panitumumab was described. These results could be useful for patient stratification in new anti-EGFR clinical trials.

Validation and clinical application of a targeted next-generation sequencing gene panel for solid and hematologic malignancies

Background

Next-generation sequencing (NGS) is a high-throughput technology that has become widely integrated in molecular diagnostics laboratories. Among the large diversity of NGS-based panels, the Trusight Tumor 26 (TsT26) enables the detection of low-frequency variants across 26 genes using the MiSeq platform.

Methods

We describe the inter-laboratory validation and subsequent clinical application of the panel in 399 patients presenting a range of tumor types, including gastrointestinal (GI, 29%), hematologic (18%), lung (13%), gynecological and breast (8% each), among others.

Results

The panel is highly accurate with a test sensitivity of 92%, and demonstrated high specificity and positive predictive values (95% and 96%, respectively). Sequencing testing was successful in two-thirds of patients, while the remaining third failed due to unsuccessful quality-control filtering. Most detected variants were observed in the TP53 (28%), KRAS (16%), APC (10%) and PIK3CA (8%) genes. Overall, 372 variants were identified, primarily distributed as missense (81%), stop gain (9%) and frameshift (7%) altered sequences and mostly reported as pathogenic (78%) and variants of uncertain significance (19%). Only 14% of patients received targeted treatment based on the variant determined by the panel. The variants most frequently observed in GI and lung tumors were: KRAS c.35G > A (p.G12D), c.35G > T (p.G12V) and c.34G > T (p.G12C).

Conclusions

Prior panel validation allowed its use in the laboratory daily practice by providing several relevant and potentially targetable variants across multiple tumors. However, this study is limited by high sample inadequacy rate, raising doubts as to continuity in the clinical setting.

Comprehensive Characterization of the Mutational Landscape in Localized Anal Squamous Cell Carcinoma

Anal squamous cell carcinoma (ASCC) is a rare neoplasm. Chemoradiotherapy is the standard of care, with no therapeutic advances achieved over the past three decades. Thus, a deeper molecular characterization of this disease is still necessary. We analyzed 46 paraffin-embedded tumor samples from patients diagnosed with primary ASCC by exome sequencing. A bioinformatics approach focused in the identification of high-impact genetic variants, which may act as drivers of oncogenesis, was performed. The relation between genetics variants and prognosis was also studied. The list of high-impact genetic variants was unique for each patient. However, the pathways in which these genes are involved are well-known hallmarks of cancer, such as angiogenesis or immune pathways. Additionally, we determined that genetic variants in BRCA2, ZNF750, FAM208B, ZNF599, and ZC3H13 genes are related with poor disease-free survival in ASCC. This may help to stratify the patient's prognosis and open new avenues for potential therapeutic intervention. In conclusion, sequencing of ASCC clinical samples appears an encouraging tool for the molecular portrait of this disease.

Genetic Profile and Functional Proteomics of Anal Squamous Cell Carcinoma: Proposal for a Molecular Classification

Anal squamous cell carcinoma is a rare tumor. Chemo-radiotherapy yields a 50% 3-year relapse-free survival rate in advanced anal cancer, so improved predictive markers and therapeutic options are needed. High-throughput proteomics and whole-exome sequencing were performed in 46 paraffin samples from anal squamous cell carcinoma patients. Hierarchical clustering was used to establish groups de novo Then, probabilistic graphical models were used to study the differences between groups of patients at the biological process level. A molecular classification into two groups of patients was established, one group with increased expression of proteins related to adhesion, T lymphocytes and glycolysis; and the other group with increased expression of proteins related to translation and ribosomes. The functional analysis by the probabilistic graphical model showed that these two groups presented differences in metabolism, mitochondria, translation, splicing and adhesion processes. Additionally, these groups showed different frequencies of genetic variants in some genes, such as ATM, SLFN11 and DST Finally, genetic and proteomic characteristics of these groups suggested the use of some possible targeted therapies, such as PARP inhibitors or immunotherapy.

Population structure of OXA-48-producing Klebsiella pneumoniae ST405 isolates during a hospital outbreak characterised by genomic typing

OBJECTIVES

The aim of this study was to investigate the structure of a broad and sustained hospital outbreak of OXA-48-producing Klebsiella pneumoniae (KpO48) belonging to sequence type 405 (ST405).

METHODS

Whole-genome sequencing and comparison of ten ST405 KpO48 isolates obtained from clinical samples in our hospital was performed. Using stringent criteria, 36 single nucleotide polymorphisms (SNPs) were detected (range 0-21 in pairwise comparisons), and allele-specific PCR was used to call the SNPs among a larger set of isolates.

RESULTS

Several haplotypes were identified within the population. The haplotypes did not show a spatial structure, but a temporal evolution of sequential haplotype replacements was observed.

CONCLUSIONS

The dispersed spatial distribution suggests a reservoir formed by a large pool of colonised patients, and the temporal replacement pattern suggests that the sustained outbreak was composed of several small outbreaks that appeared and rapidly dispersed to several units.

The transcriptional and mutational landscapes of lipid metabolism-related genes in colon cancer

Metabolic alterations encountered in tumors are well recognized and considered as a hallmark of cancer. In addition to Warburg Effect, epidemiological and experimental studies support the crucial role of lipid metabolism in colorectal cancer (CRC). The overexpression of four lipid metabolism-related genes (ABCA1, ACSL1, AGPAT1 and SCD genes) has been proposed as prognostic marker of stage II CRC (ColoLipidGene signature).

In order to explore in depth the transcriptomic and genomic scenarios of ABCA1, ACSL1, AGPAT1 and SCD genes, we performed a transcriptomic meta-analysis in more than one thousand CRC individuals. Additionally we analyzed their genomic coding sequence in 95 patients, to find variants that could orchestrate CRC prognosis.

We found that genetic variant rs3071, located on SCD gene, defines a 9.77% of stage II CRC patients with high risk of death. Moreover, individuals with upregulation of ABCA1 and AGPAT1 expression have an increased risk of CRC recurrence, independently of tumor stage.

ABCA1 emerges as one of the main contributors to signature’s prognostic effect. Indeed, both high ABCA1 expression and presence of tumoral genetic variants located in ABCA1 coding region, seem to be associated with CRC risk of death. In addition the non-synonymous polymorphism rs2230808, located on ABCA1, is associated with gene expression. Patients carrying at least one copy of minor allele showed higher levels of ABCA1 expression than patients carrying homozygous major allele.

This study broaden the prognostic value of ABCA1, ACSL1, AGPAT1 and SCD genes, independently of CRC tumor stage, leading to future precision medicine approaches and “omics”-guided therapies.

Mobility of the native Bacillus subtilis conjugative plasmid pLS20 is regulated by intercellular signaling

Horizontal gene transfer mediated by plasmid conjugation plays a significant role in the evolution of bacterial species, as well as in the dissemination of antibiotic resistance and pathogenicity determinants. Characterization of their regulation is important for gaining insights into these features. Relatively little is known about how conjugation of Gram-positive plasmids is regulated. We have characterized conjugation of the native Bacillus subtilis plasmid pLS20. Contrary to the enterococcal plasmids, conjugation of pLS20 is not activated by recipient-produced pheromones but by pLS20-encoded proteins that regulate expression of the conjugation genes. We show that conjugation is kept in the default “OFF” state and identified the master repressor responsible for this. Activation of the conjugation genes requires relief of repression, which is mediated by an anti-repressor that belongs to the Rap family of proteins. Using both RNA sequencing methodology and genetic approaches, we have determined the regulatory effects of the repressor and anti-repressor on expression of the pLS20 genes. We also show that the activity of the anti-repressor is in turn regulated by an intercellular signaling peptide. Ultimately, this peptide dictates the timing of conjugation. The implications of this regulatory mechanism and comparison with other mobile systems are discussed.

Bacteria evolve rapidly due to their short generation time and their ability to exchange genetic material, which can occur via different processes, collectively named Horizontal Gene Transfer (HGT). Most bacteria contain, besides a single chromosome, autonomously replicating units called plasmids. Many plasmids carry genes enabling them to be transferred into plasmid-free bacteria. This process, called conjugation, contributes significantly to HGT. Many plasmids also contain antibiotic resistance genes. Therefore, plasmid conjugation plays a major role in the spread of antibiotic resistance. Understanding the regulation of conjugation genes is essential for designing strategies to combat the spread of antibiotic resistance. We have studied the regulation of the native plasmid pLS20 from Bacillus subtilis. Besides being a soil bacterium, B. subtilis is a gut commensal in animals and humans. Here we unraveled the mechanisms controlling conjugation and found that pLS20 conjugation genes become activated when plasmid-free recipient cells are present. We have identified the repressor protein that keeps conjugation in an ‘OFF’ state, and an anti-repressor that activates conjugation. The activity of the anti-repressor is inhibited by a pLS20-encoded peptide that is secreted from the cell and can be absorbed by cells, after a secondary processing step. Ultimately, it is the signaling-peptide that dictates when conjugation genes become activated.

Prevalence of CYP2C9 polymorphisms in the south of Europe

CYP2C9 is a major liver enzyme responsible of the metabolism of many clinically important drugs. The presence of CYP2C9 genetic polymorphisms has been associated with marked interindividual variability in its catalytic activity that could result in drug toxicity. Here we present frequencies of the most common CYP2C9 coding variants CYP2C9*2 (C430T) and CYP2C9*3 (A1075C) in representative samples of four regions from Spain (Basque Country, n=358; Catalonia, n=240; Central Spain, n=190 and Galicia, n=288) and one northern Italian region, (Verona, n=164), which range between 0.125 and 0.165 in the case of CYP2C9*2 and between 0.071 and 0.085 for CYP2C9*3. No significant differences between CYP2C9 allele frequencies were found comparing all the sampled populations. A more extensive comparative analysis using allele frequency data of populations widely spread over Europe was performed, showing significant differences in the CYP2C9*2 allele frequencies distribution between some of the regions, being quite homogeneous in the case of CYP2C9*3 variant. The results obtained show that above 40% of our samples carry a mutate allele, which can result in a poor metabolization of low therapeutic index drugs as oral anticoagulants (warfarin, acenocoumarol), oral antidiabetic drugs and some non-steroidal anti-inflammatory drugs. Our study constitutes both a large (n=1240) and robust allele frequency database on CYP2C9 polymorphisms, which represents one of the most numerous CYP2C9*2 and *3 database existing to date.

Analysis of the human G protein-coupled receptor kinase 2 (GRK2) gene promoter: regulation by signal transduction systems in aortic smooth muscle cells

BACKGROUND

Desensitization of G protein-coupled receptors (GPCR) is emerging as an important feature of several cardiovascular diseases. G protein-coupled receptor kinase 2 (GRK2) plays a key role in the regulation of a variety of these receptors, and its cardiac expression levels are altered in pathological situations such as chronic heart failure. However, very little is known about the signals and mechanisms that modulate GRK2 expression in cardiovascular cells.

METHODS AND RESULTS

We have studied the transcriptional activity of the 1.6-kb-long proximal genomic region of the human GRK2 gene. In an aortic smooth muscle cell line, agents that lead to physiological vasoconstriction and hypertrophy, such as phorbol esters, increased GRK2 promoter activity. Activation of signaling pathways by cotransfected G(alphaq) subunits or alpha(1)-adrenergic receptors also markedly enhanced the expression of the GRK2 promoter constructs. Conversely, proinflammatory cytokines, such as interleukin-1beta, tumor necrosis factor-alpha, or interferon-gamma, led to the opposite effect, decreasing the activity of the GRK2 promoter.

CONCLUSIONS

Our results suggest that the expression of GRK2 in vascular cells is tightly controlled at the transcriptional level by the interplay between several extracellular messengers, which may trigger alterations of normal GRK2 levels in some physiopathological circumstances, thus promoting changes in the efficacy of the GPCR signal transduction.

The gene coding for the beta-chain of C4b-binding protein (C4BPB) has become a pseudogene in the mouse

C4BP beta is one of the two polypeptides that in humans compose the plasma glycoprotein C4b-binding protein (C4BP). C4BP beta binds the anticoagulant vitamin K-dependent protein S. Two, nonmutually exclusive, roles have been proposed for the C4BP-protein S interaction. It has been suggested to play a role in the control of the protein C anticoagulatory pathway. In addition, it may serve an important role in localizing C4BP to the surface of injured or activated cells. While the physiological significance of C4BP-protein S interaction is unclear, it has clinical relevance because elevated plasma levels of C4BP are associated with increased risk for thromboembolic disorders in humans, due to an inactivation of the protein C anticoagulatory pathway. Using a human C4BP beta cDNA probe, we have isolated and characterized a genomic DNA fragment that includes the murine C4BPB gene. Murine C4BPB is a single-copy gene that maps close to the C4BPA gene in chromosome 1. It contains two exons homologous to the exons coding for the SCR-1 and SCR-2 repeats of the human C4BP beta polypeptide chain. Sequence analysis of the C4BPB exons in the Mus musculus inbred strains CBA, Balb/c, and C57BL/6, in pen-bred Swiss mice, and in Mus spretus demonstrated the presence of two in-phase stop codons that are incompatible with the expression of a functional C4BP beta polypeptide. Thus, the characterization of the murine C4BPB gene documents the peculiar situation of a single-copy gene that is functional in humans but has become a pseudogene in the mouse.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of T-cell proliferation by rat synoviocytes

Antigen presentation by synoviocytes to arthritis-related T-cell clones was studied in Lewis rats. Freshly isolated synoviocytes may be able to take up and process mycobacterial antigens but they seem inefficient as antigen presenting cells. Furthermore, synovial cells inhibited the specific proliferative responses of T lymphocytes by a mechanism which apparently was not antigen-specific or mediated by secreted cytokines. Synovial cells isolated from rats at the period of developing adjuvant arthritis showed a lower inhibitory capacity associated with a lower degree of antigen clearance. These results suggest that synoviocytes might inhibit T-cell responses in normal joints and that this negative control diminishes following arthritis induction.

Aggregated human immunoglobulins bind to modified proteins

Human immunoglobulins treated at 55 degrees C in vitro are able to interact with maleylated bovine serum albumin (mBSA), but not with unmodified BSA. Gel filtration experiments demonstrated that the mBSA binding is associated with a high molecular weight complex of aggregated IgG. This aggregated IgG with binding capacity for mBSA could also be generated in vitro by treatment of human IgG at 37 degrees C or 40 degrees C and by incubation with human neutrophils. Furthermore, IgG aggregates with binding activity for mBSA could be detected in untreated synovial fluids from rheumatoid arthritis patients, indicating that these complexes occur in vivo. The phenomenon of binding to aggregated IgG was extended to other modified proteins such as maleylated human serum albumin (mHSA), acetyl low density lipoprotein (Ac-LDL) and BSA reacted with oxidized linolenic acid. Soluble forms of these modified proteins were able to compete for the interaction between aggregated IgG and surface-bound mBSA. We also found that aggregated IgG enhanced the Ac-LDL-dependent foam cell formation. These findings suggest a role for aggregated IgG in the metabolism of oxidized proteins.

Decreased tubulin synthesis in synoviocytes from adjuvant-induced arthritic rats

The first microscopical alterations along adjuvant arthritis induction in rats seem to appear in the synovium. We have studied the protein synthesis pattern of the cells constitutively present in synovial membrane (synoviocytes) and have found an impairment of synthesis of some proteins when synoviocytes are derived from adjuvant arthritic rats. One of these polypeptides was identified as beta tubulin by two-dimensional gel electrophoresis, a membrane transfer assay using a specific monoclonal antibody and peptide mapping. We postulate that a repressed synthesis of tubulin may be an initial step in the triggering of the disease, since the effect was evident at pre-arthritic stages, when infiltration by inflammatory cells had not yet occurred.

Arthritis transferred by cells derived from pre-inflammatory rat synovium

Different cell populations isolated from rats during the period of latency of adjuvant arthritis were injected into the bloodstream of naive rats to test their ability to transfer articular disorders. Synovium-derived cells (synoviocytes) were able to induce arthritis in 3 out of 4 recipient animals, whereas peripheral blood leukocytes, peritoneal exudate macrophages, lymph node cells, synoviocyte lysates and synoviocytes from control animals were not able to do so. This model of cellular transferred arthritis is associated with antibody titres to hsp65 in rat sera. Our findings suggest a crucial role for synovial cells in the pathogenesis of adjuvant disease, which might be linked to their function as accessory cells.

Cellular and humoral reactivity pattern to the mycobacterial heat shock protein HSP65 in adjuvant arthritis susceptible and resistant Wistar rats

We have analyzed the cellular and humoral immunity to the mycobacterial 65 KDa heat shock protein (hsp65) in a group of Freund's Adjuvant-immunized rats with a limited susceptibility to Adjuvant arthritis. According to the arthritis indices during the period of study (35 days), two different groups of rats could be distinguished; a) autoimmune Adjuvant arthritic rats (AA), and b) Non-arthritic animals (NA), including both rats which did not display any disease symptoms and rats suffering mild transient inflammation. The cellular response to the immunizing agent (Mycobacterium tuberculosis) or the mitogen Concanavalin A was comparable between both groups of rats. However, we detected an impaired cellular response to the individual hsp65 antigen in the animals that did not develop the disease. On the contrary, the level of hsp65-specific antibodies was much higher in NA animals than in AA rats suggesting a protective role for the hsp65 specific antibodies.