Search

Objective: To measure neurone-specific humoral and cellular immune parameters in MRI-positive patients with multiple sclerosis (MS).Background: It has been postulated from animal models for MS and in situ evidence in MS patients that antibodies, activated T cells and proinflammatory cytokines are involved in the destruction of myelin sheaths and loss of oligodendrocytes in active areas.Subjects and Methods: Blood samples were obtained from 20 healthy control subjects and 20 patients with abnormal MRI and clinical diagnosis of MS. Sera were tested for levels of IgG, IgM and IgA against myelin basic protein (MBP), myelin oligodendrocyte glycoprotein (MOG) peptides, and a small heat-shock protein, alpha-beta-crystallin. Lymphocytes were isolated and cultured in the presence or absence of MBP, MOG peptides and alpha-beta-crystallin, measured for stimulated T cells, cytokine production and compared with controls.Results: Patients with MS showed the highest levels of IgG, IgM or IgA antibodies against one or all three tested antigens. Moreover, in the presence of MBP, MOG peptides or alpha-beta-crystallin, a significant percent- age of lymphocytes from MS patients underwent blast transformation, which resulted in high levels of interferon gamma (IFN-gamma), tumour necrosis factor alpha (TNF-alpha) and tumour necrosis factor beta (TNF-beta) production. Sensitivity of these assays was 60-80% and specificity, 65-70%.Conclusions: Detection of antibodies against MBP, MOG peptides, alpha-beta-crystallin, lymphocyte stimulation and production of proinflammatory cytokines in response to these antigens could be used as surrogate markers for the confirmation of MS diagnosis. A combination of antibodies, lymphocyte activation or cytokine production with abnormal MRI may significantly increase the sensitivity and specificity of MS diagnosis. [ABSTRACT FROM AUTHOR]

Natural killer (NK) cells and cytotoxic T (CD8 + ) cells are two of the most important types of immune cells in our body, protecting it from deadly invaders. While the NK cell is part of the innate immune system, the CD8 + cell is one of the major components of adaptive immunity. Still, these two very different types of cells share the most important function of destroying pathogen-infected and tumorous cells by releasing cytotoxic granules that promote proteolytic cleavage of harmful cells, leading to apoptosis. In this review, we look not only at NK and CD8 + T cells but also pay particular attention to their different subpopulations, the immune defenders that include the CD56 + CD16 dim , CD56 dim CD16 + , CD57 + , and CD57 + CD16 + NK cells, the NKT, CD57 + CD8 + , and KIR + CD8 + T cells, and ILCs. We examine all these cells in relation to their role in the protection of the body against different microorganisms and cancer, with an emphasis on their mechanisms and their clinical importance. Overall, close collaboration between NK cells and CD8 + T cells may play an important role in immune function and disease pathogenesis. The knowledge of how these immune cells interact in defending the body against pathogens and cancers may help us find ways to optimize their defensive and healing capabilities with methods that can be clinically applied., Competing Interests: Authors Aristo Vojdani, Sadi Koksoy and Mark Engelman are employed by the companies Immunosciences Lab, Inc. andCyrex Labs., LLC. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Age is a significant risk factor for the coronavirus disease 2019 (COVID-19) severity due to immunosenescence and certain age-dependent medical conditions (e.g., obesity, cardiovascular disorder, and chronic respiratory disease). However, despite the well-known influence of age on autoantibody biology in health and disease, its impact on the risk of developing severe COVID-19 remains poorly explored. Here, we performed a cross-sectional study of autoantibodies directed against 58 targets associated with autoimmune diseases in 159 individuals with different COVID-19 severity (71 mild, 61 moderate, and 27 with severe symptoms) and 73 healthy controls. We found that the natural production of autoantibodies increases with age and is exacerbated by SARS-CoV-2 infection, mostly in severe COVID-19 patients. Multiple linear regression analysis showed that severe COVID-19 patients have a significant age-associated increase of autoantibody levels against 16 targets (e.g., amyloid β peptide, β catenin, cardiolipin, claudin, enteric nerve, fibulin, insulin receptor a, and platelet glycoprotein). Principal component analysis with spectrum decomposition and hierarchical clustering analysis based on these autoantibodies indicated an age-dependent stratification of severe COVID-19 patients. Random forest analysis ranked autoantibodies targeting cardiolipin, claudin, and platelet glycoprotein as the three most crucial autoantibodies for the stratification of severe COVID-19 patients ≥50 years of age. Follow-up analysis using binomial logistic regression found that anti-cardiolipin and anti-platelet glycoprotein autoantibodies significantly increased the likelihood of developing a severe COVID-19 phenotype with aging. These findings provide key insights to explain why aging increases the chance of developing more severe COVID-19 phenotypes., (© 2023. Springer Nature Limited.)

A novel syndrome called long-haul COVID or long COVID is increasingly recognized in a significant percentage of individuals within a few months after infection with SARS-CoV-2. This disorder is characterized by a wide range of persisting, returning or even new but related symptoms that involve different tissues and organs, including respiratory, cardiac, vascular, gastrointestinal, musculo-skeletal, neurological, endocrine and systemic. Some overlapping symptomatologies exist between long COVID and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Very much like with long ME/CFS, infections with herpes family viruses, immune dysregulation, and the persistence of inflammation have been reported as the most common pattern for the development of long COVID. This review describes several factors and determinants of long COVID that have been proposed, elaborating mainly on viral persistence, reactivation of latent viruses such as Epstein-Barr virus and human herpesvirus 6 which are also associated with the pathology of ME/CFS, viral superantigen activation of the immune system, disturbance in the gut microbiome, and multiple tissue damage and autoimmunity. Based on these factors, we propose diagnostic strategies such as the measurement of IgG and IgM antibodies against SARS-CoV-2, EBV, HHV-6, viral superantigens, gut microbiota, and biomarkers of autoimmunity to better understand and manage this multi-factorial disorder that continues to affect millions of people in the world.

It has been shown that SARS-CoV-2 shares homology and cross-reacts with vaccines, other viruses, common bacteria and many human tissues. We were inspired by these findings, firstly, to investigate the reaction of SARS-CoV-2 monoclonal antibody with different pathogens and vaccines, particularly DTaP. Additionally, since our earlier studies have shown immune reactivity by antibodies made against pathogens and autoantigens towards different food antigens, we also studied cross-reaction between SARS-CoV-2 and common foods. For this, we reacted monoclonal and polyclonal antibodies against SARS-CoV-2 spike protein and nucleoprotein with 15 different bacterial and viral antigens and 2 different vaccines, BCG and DTaP, as well as with 180 different food peptides and proteins. The strongest reaction by SARS-CoV-2 antibodies were with DTaP vaccine antigen, E. faecalis , roasted almond, broccoli, soy, cashew, α+β casein and milk, pork, rice endochitinase, pineapple bromelain, and lentil lectin. Because the immune system tends to form immune responses towards the original version of an antigen that it has encountered, this cross-reactivity may have its advantages with regards to immunity against SARS-CoV-2, where the SARS-CoV-2 virus may elicit a "remembered" immune response because of its structural similarity to a pathogen or food antigen to which the immune system was previously exposed. Our findings indicate that cross-reactivity elicited by DTaP vaccines in combination with common herpesviruses, bacteria that are part of our normal flora such as E. faecalis , and foods that we consume on a daily basis should be investigated for possible cross-protection against COVID-19. Additional experiments would be needed to clarify whether or not this cross-protection is due to cross-reactive antibodies or long-term memory T and B cells in the blood., Competing Interests: Corresponding author Aristo Vojdani is the co-owner, CEO and Technical Director of Immunosciences Lab., Inc. He is also the Chief Scientific Advisor of Cyrex Labs, LLC on a consultancy basis. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be constructed as a potential conflict of interest., (Copyright © 2022 Vojdani, Vojdani, Melgar and Redd.)

In our continuing examination of the role of exposomes in autoimmune disease, we use this review to focus on pathogens. Infections are major contributors to the pathophysiology of autoimmune diseases through various mechanisms, foremost being molecular mimicry, when the structural similarity between the pathogen and a human tissue antigen leads to autoimmune reactivity and even autoimmune disease. The three best examples of this are oral pathogens, SARS-CoV-2, and the herpesviruses. Oral pathogens reach the gut, disturb the microbiota, increase gut permeability, cause local inflammation, and generate autoantigens, leading to systemic inflammation, multiple autoimmune reactivities, and systemic autoimmunity. The COVID-19 pandemic put the spotlight on SARS-CoV-2, which has been called "the autoimmune virus." We explore in detail the evidence supporting this. We also describe how viruses, in particular herpesviruses, have a role in the induction of many different autoimmune diseases, detailing the various mechanisms involved. Lastly, we discuss the microbiome and the beneficial microbiota that populate it. We look at the role of the gut microbiome in autoimmune disorders, because of its role in regulating the immune system. Dysbiosis of the microbiota in the gut microbiome can lead to multiple autoimmune disorders. We conclude that understanding the precise roles and relationships shared by all these factors that comprise the exposome and identifying early events and root causes of these disorders can help us to develop more targeted therapeutic protocols for the management of this worldwide epidemic of autoimmunity.

Autoimmune diseases affect 5-9% of the world's population. It is now known that genetics play a relatively small part in the pathophysiology of autoimmune disorders in general, and that environmental factors have a greater role. In this review, we examine the role of the exposome, an individual's lifetime exposure to external and internal factors, in the pathophysiology of autoimmune diseases. The most common of these environmental factors are toxic chemicals, food/diet, and infections. Toxic chemicals are in our food, drink, common products, the air, and even the land we walk on. Toxic chemicals can directly damage self-tissue and cause the release of autoantigens, or can bind to human tissue antigens and form neoantigens, which can provoke autoimmune response leading to autoimmunity. Other types of autoimmune responses can also be induced by toxic chemicals through various effects at the cellular and biochemical levels. The food we eat every day commonly has colorants, preservatives, or packaging-related chemical contamination. The food itself may be antigenic for susceptible individuals. The most common mechanism for food-related autoimmunity is molecular mimicry, in which the food's molecular structure bears a similarity with the structure of one or more self-tissues. The solution is to detect the trigger, remove it from the environment or diet, then repair the damage to the individual's body and health.

Introduction: Parkinson's disease is characterized by non-motor/motor dysfunction midbrain neuronal death and α-synuclein deposits. The accepted hypothesis is that unknown environmental factors induce α-synuclein accumulation in the brain via the enteric nervous system., Material and Methods: Monoclonal antibodies made against recombinant α-synuclein protein or α-synuclein epitope 118-123 were applied to the antigens of 180 frequently consumed food products. The specificity of those antibody-antigen reactions was confirmed by serial dilution and inhibition studies. The Basic Local Alignment Search Tool sequence matching program was used for sequence homologies., Results: While the antibody made against recombinant α-synuclein reacted significantly with 86/180 specific food antigens, the antibody made against α-synuclein epitope 118-123 reacted with only 32/180 tested food antigens. The food proteins with the greatest number of peptides that matched with α-synuclein were yeast, soybean, latex hevein, wheat germ agglutinin, potato, peanut, bean agglutinin, pea lectin, shrimp, bromelain, and lentil lectin. Conclusions: The cross-reactivity and sequence homology between α-synuclein and frequently consumed foods, reinforces the autoimmune aspect of Parkinson's disease. It is hypothesized that luminal food peptides that share cross-reactive epitopes with human α-synuclein and have molecular similarity with brain antigens are involved in the synucleinopathy. The findings deserve further confirmation by extensive research.

We sought to determine whether immune reactivity occurs between anti-SARS-CoV-2 protein antibodies and human tissue antigens, and whether molecular mimicry between COVID-19 viral proteins and human tissues could be the cause. We applied both human monoclonal anti-SARS-Cov-2 antibodies (spike protein, nucleoprotein) and rabbit polyclonal anti-SARS-Cov-2 antibodies (envelope protein, membrane protein) to 55 different tissue antigens. We found that SARS-CoV-2 antibodies had reactions with 28 out of 55 tissue antigens, representing a diversity of tissue groups that included barrier proteins, gastrointestinal, thyroid and neural tissues, and more. We also did selective epitope mapping using BLAST and showed similarities and homology between spike, nucleoprotein, and many other SARS-CoV-2 proteins with the human tissue antigens mitochondria M2, F-actin and TPO. This extensive immune cross-reactivity between SARS-CoV-2 antibodies and different antigen groups may play a role in the multi-system disease process of COVID-19, influence the severity of the disease, precipitate the onset of autoimmunity in susceptible subgroups, and potentially exacerbate autoimmunity in subjects that have pre-existing autoimmune diseases. Very recently, human monoclonal antibodies were approved for use on patients with COVID-19. The human monoclonal antibodies used in this study are almost identical with these approved antibodies. Thus, our results can establish the potential risk for autoimmunity and multi-system disorders with COVID-19 that may come from cross-reactivity between our own human tissues and this dreaded virus, and thus ensure that the badly-needed vaccines and treatments being developed for it are truly safe to use against this disease., Competing Interests: AV is the co-owner, CEO and employee of Immunosciences Lab., Inc. EV is the owner and employee of Regenera Medical, a private medical practice. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Vojdani, Vojdani and Kharrazian.)

Individuals with intestinal barrier dysfunction are more prone to autoimmunity. Lipopolysaccharides (LPS) from gut bacteria have been shown to play a role in systemic inflammation, leading to the opening of the gut and blood-brain barrier (BBB). This study aims to measure antibodies against LPS and barrier proteins in samples positive for anti- Saccharomyces cerevisiae antibodies (ASCA) and anti-neutrophil cytoplasmic antibodies (ANCA) and compare them with these same antibodies in controls to determine whether a correlation between LPS and barrier proteins could be found. We obtained 94 ASCA- and 94 ANCA-positive blood samples, as well as 188 blood samples from healthy controls. Samples were assessed for antibodies to LPS, zonulin+occludin, S100B, and aquaporin-4 (AQP4). Results show significant elevation in antibodies in about 30% of ASCA- and ANCA-positive sera and demonstrate positive linear relationships between these antibodies. The findings suggest that individuals positive for ASCA and ANCA have increased odds of developing intestinal and BBB permeability compared to healthy subjects. The levels of LPS antibodies in both ASCA- and ANCA-positive and negative specimens showed from low and moderate to high correlation with antibodies to barrier proteins. This study shows that LPS, by damaging the gut and BBBs, contribute to the extra-intestinal manifestation of IBD. We conclude that IBD patients should be screened for LPS antibodies in an effort to detect or prevent possible barrier damage at the earliest stage possible to abrogate disease symptoms in IBS and associated disorders., Competing Interests: The authors declare no conflict of interest.

The aim of this study was to examine the direct reaction of specific lectin/agglutinin antibodies to different tissue antigens to confirm the theory that reactivity between them may contribute to autoimmunities. Lectins are carbohydrate-binding proteins found in nearly all fruits and vegetables. Undigested lectins can penetrate the gut barriers, provoking an immune response that results in the production of antibodies against them. Using an enzyme-linked immunosorbent assay, we reacted lectin-specific antibodies with 62 different tissue antigens. Wheat germ agglutinin-specific antibody was the most reactive with the tissue antigens (37 tissues out of 62), followed by red kidney bean phytohemagglutinin-specific antibody (20), soybean agglutinin-specific antibody (20), and peanut agglutinin-specific antibody (15). This reaction between anti-lectin antibodies and many human tissue antigens may be due to possible molecular mimicry and cross-reactivity. After our results confirmed that anti-lectin antibodies bind with human tissues, we wanted to determine the prevalence of these antibodies in the blood of 500 nominally healthy donors. The percentage elevation of antibodies against different lectins ranged from 12 to 16% (Immunoglobulin G), 9.7-14.7% (Immunoglobulin A), 12-18% (Immunoglobulin M), and 7.8-14.6% (Immunoglobulin E). Serial dilutions and inhibition study confirmed that these reactions were specific. Finally, we tested the lectin-specific antibody level in sera both negative and positive for RF and ANA and found that IgM anti-lectin antibody levels were highly correlated with RF but not with ANA level. The reaction of anti-lectin antibodies with human tissue components and their detection in RF-positive samples may describe mechanisms by which the production of antibodies against undigested lectins may contribute to the pathogenesis of some autoimmune diseases., Competing Interests: The authors declares that there are no conflicts of interest regarding the publication of this paper., (Copyright © 2020 Aristo Vojdani et al.)

Background: The bacteria Campylobacter jejuni ( C. jejuni ) is commonly associated with Guillane-Barré syndrome (GBS) and irritable bowel syndrome (IBS), but studies have also linked it with Miller Fisher syndrome, reactive arthritis and other disorders, some of which are autoimmune. It is possible that C. jejuni and its toxins may be cross-reactive with some human tissues and food antigens, potentially leading to autoimmune responses., Aim: To measure the immune reactivity of C. jejuni and C. jejuni cytolethal distending toxin (Cdt) antibodies with tissue and food antigens to examine their role in autoimmunities., Methods: Using enzyme-linked immunosorbent assay (ELISA) methodology, specific antibodies made against C. jejuni and C. jejuni Cdt were applied to a variety of microwell plates coated with 45 tissues and 180 food antigens. The resulting immunoreactivities were compared to reactions with control wells coated with human serum albumin (HSA) which were used as negative controls and with wells coated with C. jejuni lysate or C. jejuni Cdt which served as positive controls., Results: At 3 SD above the mean of control wells coated with HSA or 0.41 OD, the mouse monoclonal antibody made against C. jejuni showed moderate to high reactions with zonulin, somatotropin, acetylcholine receptor, β-amyloid and presenilin. This immune reaction was low with an additional 25 tissue antigens including asialoganglioside, and the same antibody did not react at all with another 15 tissue antigens. Examining the reaction between C. jejuni antibody and 180 food antigens, we found insignificant reactions with 163 foods but low to high immune reactions with 17 food antigens. Similarly, we examined the reaction of C. jejuni Cdt with the same tissues and food antigens. The strongest reactions were observed with zonulin, intrinsic factor and somatotropin. The reaction was moderate with 9 different tissue antigens including thyroid peroxidase, and reaction was low with another 10 different antigens, including neuronal antigens. The reaction of C. jejuni Cdt antibody with an additional 23 tissue antigens was insignificant. Regarding the reaction of C. jejuni Cdt antibody with different food antigens, 160 out of 180 foods showed insignificant reactions, while 20 foods showed reactions ranging from low to high., Conclusion: Our findings indicate that C. jejuni and its Cdt may play a role in inflammation and autoimmunities beyond the gut., Competing Interests: Conflict-of-interest statement: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Antibodies against many neural antigens are detected in the sera of both patients with Alzheimer's disease (AD) and some healthy individuals. Blood-brain barrier dysfunction could make it possible for brain-reactive autoantibodies to reach the brain, where they can react with amyloid ß peptide (AßP). The origin of these autoreactive antibodies in the blood is unclear. The goals of this study were as follows: (1) to examine the immune reactivity of anti-AßP-42 with 22 neuronal and other associated antigens, some of which are involved in the pathophysiology of AD; (2) to classify antibodies to these 22 different antigens into those that cross-react with AßP-42 and those that do not; (3) to determine whether these antibodies react with BBB proteins, nerve growth factors, and enteric neuronal antigens. Using monoclonal AßP-42 antibody and ELISA methodology, we found that the antibody was highly reactive with Aß protein, tau protein, presenilin, rabaptin-5, β -NGF, BDNF, mTG, and enteric nerve. The same antibody produced equivocal to moderate reactions with glutamate-R, S100B, AQP4, GFAP, MBP, α -synuclein, tTG-2, and tTG-3, and not with the rest. These antibodies were also measured in blood samples from 47 AD patients and 47 controls. IgG antibodies were found to be elevated against AßP-42 and many other antigens in a significant percentage of controls. Overall, the mean OD values were significantly higher against 9/23 tested antigens ( p <0.001) in the samples with AD. We were indeed able to classify the detected neuronal antibodies into those that cross-react with AßP-42 and those that do not. Our main finding is that although these antibodies may be harmless in a subgroup of controls, in individuals with compromised BBBs these antibodies that cross-react with AßP-42 can reach the brain, where their cross-reactivity with AßP-42 may contribute to the onset and progression of AD, and perhaps other neurodegenerative disorders.

Aim: To evaluate the measurement of zonulin level and antibodies of zonulin and other tight junction proteins in the blood of controls and celiac disease patients., Methods: This study was conducted to assess the variability or stability of zonulin levels vs IgA and IgG antibodies against zonulin in blood samples from 18 controls at 0, 6, 24 and 30 h after blood draw. We also measured zonulin level as well as zonulin, occludin, vinculin, aquaporin 4 and glial fibrillary acidic protein antibodies in the sera of 30 patients with celiac disease and 30 controls using enzyme-linked immunosorbent assay methodology., Results: The serum zonulin level in 6 out of 18 subjects was low or < 2.8 ng/mL and was very close to the detection limit of the assay. The other 12 subjects had zonulin levels of > 2.8 ng/mL and showed significant fluctuation from sample to sample. Comparatively, zonulin antibody measured in all samples was highly stable and reproducible from sample to sample. Celiac disease patients showed zonulin levels with a mean of 8.5 ng/mL compared to 3.7 ng/mL in controls ( P < 0.0001). Elevation of zonulin level at 2SD above the mean was demonstrated in 37% of celiac disease patients, while antibodies against zonulin, occludin and other tight junction proteins was detected in up to 86% of patients with celiac disease., Conclusion: Due to its fluctuation, a single measurement of zonulin level is not recommended for assessment of intestinal barrier integrity. Measurement of IgG and IgA antibodies against zonulin, occludin, and other tight junction proteins is proposed for the evaluation of the loss of intestinal barrier integrity., Competing Interests: Conflict-of-interest statement: Dr. Aristo Vojdani is the CEO and technical director of Immunosciences Lab., Inc.

Searching for a mechanism underlying autoimmunity in autism, we postulated that gliadin peptides, heat shock protein 60 (HSP-60), and streptokinase (SK) bind to different peptidases resulting in autoantibody production against these components. We assessed this hypothesis in patients with autism and in those with mixed connective tissue diseases. Associated with antigliadin and anti-HSP antibodies, children with autism and patients with autoimmune disease developed anti-dipeptidylpeptidase I (DPP I), anti-dipeptidylpeptidase IV (DPP IV [or CD26]) and anti-aminopeptidase N (CD13) autoantibodies. A significant percentage of autoimmune and autistic sera were associated with elevated immunoglobulin G (IgG), IgM, or IgA antibodies against three peptidases, gliadin, and HSP-60. These antibodies are specific, since immune absorption demonstrated that only specific antigens (e.g., DPP IV absorption of anti-DPP IV), significantly reduced IgG, IgM, and IgA antibody levels. For direct demonstration of SK, HSP-60, and gliadin peptide binding to DPP IV, microtiter wells coated with DPP IV were reacted with SK, HSP-60, and gliadin. They were then reacted with anti-DPP IV or anti-SK, anti-HSP, and antigliadin antibodies. Adding SK, HSP-60, and gliadin peptides to DPP IV resulted in 27 to 43% inhibition of the DPP IV-anti-DPP IV reaction, but DPP IV-positive peptides caused 18 to 20% enhancement of antigen-antibody reactions. We propose that (i) superantigens (e.g., SK and HSP-60) and dietary proteins (e.g., gliadin peptides) in individuals with predisposing HLA molecules bind to aminopeptidases and (ii) they induce autoantibodies to peptides and tissue antigens. Dysfunctional membrane peptidases and autoantibody production may result in neuroimmune dysregulation and autoimmunity.

Opioid-receptor activation in cell lines results in phosphorylation of p42/44 mitogen-activated protein kinase (MAPK), which contributes to agonist-induced desensitization of adenylate cyclase signaling. In this study, morphine-induced MAPK modulation was examined in the mouse brain using antibodies against phosphorylated MAPK. Thirty minutes after systemic morphine, MAPK modulation was observed in brain areas associated with analgesia and reward. Activation of MAPK was increased in the anterior cingulate (Acc), somato-sensory and association cortices, and locus ceruleus (LC). In contrast, MAPK activation was decreased in the nucleus accumbens and central amygdala (CeA). Double-label confocal microscopy revealed that morphine-induced MAPK modulation occurred predominantly in cells not expressing mu-opioid receptors, with the exception of the LC. Furthermore, the NMDA receptor antagonist 3,3-(2-carboxypiperazine-4-yl)-propyl-1-phosphonate blocked morphine-induced MAPK modulation in several cortical areas including the Acc. We then examined morphine-induced MAPK modulation during expression of either analgesic tolerance or locomotor sensitization, which were differentiated by two repeated morphine regimens. Analgesic tolerance was accompanied by tolerance to morphine-induced MAPK modulation in all of the brain areas examined except the CeA. Locomotor sensitization resulted in sensitization to morphine-induced MAPK activation in the posterior basolateral amygdala. Additionally, a pronounced instatement of morphine-induced MAPK activation was observed in CA3 hippocampal processes. This instatement was observed during expression of tolerance; however, it was not significant during sensitization. In summary, these results provide distinct, region-specific mechanisms for morphine-induced MAPK modulation in the mouse brain and give insight into the brain circuitry involved in acute and adaptive opioid behaviors.