Autobiographical Case Report: A Rubber Band, a Glass of Orange Juice

Seemingly simple procedures can go desperately wrong. Physicians are used to "knowing" and "being in charge". When a physician is suddenly the profoundly ill patient, the inversion of roles can be frustrating, frightening, and disorienting. 

Enhanced Adhesion and OspC Protein Synthesis of the Lyme Disease Spirochete Borrelia Burgdorferi Cultivated in a Host-Derived Tissue Co-Culture System

BACKGROUND

The adhesion process of Borrelia burgdorferi to susceptible host cell has not yet been completely understood regarding the function of OspA, OspB and OspC proteins and a conflict exists in the infection process.

AIMS

The adhesion rates of pathogenic (low BSK medium passaged or susceptible rat joint tissue co-cultivated) or non-pathogenic Borrelia burgdorferi (high BSK medium passaged) isolate (FNJ) to human umbilical vein endothelial cells (HUVEC) cultured on coverslips and the synthesis of OspA and OspC proteins were investigated to analyze the infection process of this bacterium.

STUDY DESIGN

In-vitro study.

METHODS

Spirochetes were cultured in BSK medium or in a LEW/N rat tibiotarsal joint tissue feeder layer supported co-culture system using ESG co-culture medium and labelled with 3H-adenine for 48 hours. SDS-PAGE, Western Blotting, Immunogold A labeling as well as radiolabeling experiments were used to compare pathogenic or non pathogenic spirochetes during the adhesion process.

RESULTS

Tissue co-cultured B. burgdorferi adhered about ten times faster than BSK-grown spirochetes. Trypsin inhibited attachment to HUVEC and co-culture of trypsinized spirochetes with tissues reversed the inhibition. Also, the synthesis of OspC protein by spirochetes was increased in abundance after tissue co-cultures, as determined by SDS-PAGE and by electron microscopy analysis of protein A-immunogold staining by anti-OspC antibodies. OspA protein was synthesized in similar quantities in all Borrelia cultures analyzed by the same techniques.

CONCLUSION

Low BSK passaged or tissue co-cultured pathogenic Lyme disease spirochetes adhere to HUVEC faster than non-pathogenic high BSK passaged forms of this bacterium. Spirochetes synthesized OspC protein during host tissue-associated growth. However, we did not observe a reduction of OspA synthesis during host tissue co-cultivation in vitro.

Basic science for the clinician 33: interleukins of current clinical relevance (part I)

Normal orchestration of wound healing, the protective immune response and inflammation, involve a bewildering array of cells that communicate to each other locally by means of cell-surface receptors and their ligands. For local and middle- to long-distance coordination, some of these same cells make and export soluble messengers that communicate to both immune and nonimmune cells. Although all these messengers have a role in normal immune homeostasis, it is apparent that many are involved in tissue damage in a variety of diseases, eg, rheumatoid arthritis and osteoarthritis. Some of these molecules are known as interleukins. The list of interleukins (IL) is now nearing 30 and, as a result of the molecular biology revolution, we now know the direct clinical relevance of many of them. As benchtop molecular biology matures into therapeutic and diagnostic tools, clinicians must begin to master this disparate group of molecules; making this harder is the fact that unlike acronyms (often impenetrable as they might be), an IL designation does not give a clue as to the source, target, or action of the IL. IL-1 and IL-2 were the first messengers to bear the "interleukin" name 25 years ago; they are well known to rheumatologists by now, so this article deals with some of the characteristics of the other clinically relevant IL molecules starting with IL-3.

Abatacept improves health-related quality of life, pain, sleep quality, and daily participation in subjects with juvenile idiopathic arthritis

OBJECTIVE

To assess health-related quality of life (HRQOL) in abatacept-treated children/adolescents with juvenile idiopathic arthritis (JIA).

METHODS

In this phase III, double-blind, placebo-controlled trial, subjects with active polyarticular course JIA and an inadequate response/intolerance to ≥1 disease-modifying antirheumatic drug (including biologics) received abatacept 10 mg/kg plus methotrexate (MTX) during the 4-month open-label period (period A). Subjects achieving the American College of Rheumatology Pediatric 30 criteria for improvement (defined "responders") were randomized to abatacept or placebo (plus MTX) in the 6-month double-blind withdrawal period (period B). HRQOL assessments included 15 Child Health Questionnaire (CHQ) health concepts plus the physical (PhS) and psychosocial summary scores (PsS), pain (100-mm visual analog scale), the Children's Sleep Habits Questionnaire, and a daily activity participation questionnaire.

RESULTS

A total of 190 subjects from period A and 122 from period B were eligible for analysis. In period A, there were substantial improvements across all of the CHQ domains (greatest improvement was in pain/discomfort) and the PhS (8.3 units) and PsS (4.3 units) with abatacept. At the end of period B, abatacept-treated subjects had greater improvements versus placebo in all domains (except behavior) and both summary scores. Similar improvement patterns were seen with pain and sleep. For participation in daily activities, an additional 2.6 school days/month and 2.3 parents' usual activity days/month were gained in period A responders with abatacept, and further gains were made in period B (1.9 versus 0.9 [P = 0.033] and 0.2 versus -1.3 [P = 0.109] school days/month and parents' usual activity days/month, respectively, in abatacept- versus placebo-treated subjects).

CONCLUSION

Improvements in HRQOL were observed with abatacept, providing real-life tangible benefits to children with JIA and their parents/caregivers.

Long-term safety and efficacy of abatacept in children with juvenile idiopathic arthritis

OBJECTIVE

We previously documented that abatacept was effective and safe in patients with juvenile idiopathic arthritis (JIA) who had not previously achieved a satisfactory clinical response with disease-modifying antirheumatic drugs or tumor necrosis factor blockade. Here, we report results from the long-term extension (LTE) phase of that study.

METHODS

This report describes the long-term, open-label extension phase of a double-blind, randomized, controlled withdrawal trial in 190 patients with JIA ages 6-17 years. Children were treated with 10 mg/kg abatacept administered intravenously every 4 weeks, with or without methotrexate. Efficacy results were based on data derived from the 153 patients who entered the open-label LTE phase and reflect >or=21 months (589 days) of treatment. Safety results include all available open-label data as of May 7, 2008.

RESULTS

Of the 190 enrolled patients, 153 entered the LTE. By day 589, 90%, 88%, 75%, 57%, and 39% of patients treated with abatacept during the double-blind and LTE phases achieved responses according to the American College of Rheumatology (ACR) Pediatric 30 (Pedi 30), Pedi 50, Pedi 70, Pedi 90, and Pedi 100 criteria for improvement, respectively. Similar response rates were observed by day 589 among patients previously treated with placebo. Among patients who had not achieved an ACR Pedi 30 response at the end of the open-label lead-in phase and who proceeded directly into the LTE, 73%, 64%, 46%, 18%, and 5% achieved ACR Pedi 30, Pedi 50, Pedi 70, Pedi 90, and Pedi 100 responses, respectively, by day 589 of the LTE. No cases of tuberculosis and no malignancies were reported during the LTE. Pneumonia developed in 3 patients, and multiple sclerosis developed in 1 patient.

CONCLUSION

Abatacept provided clinically significant and durable efficacy in patients with JIA, including those who did not initially achieve an ACR Pedi 30 response during the initial 4-month open-label lead-in phase.

Psychiatric comorbidity and other psychological factors in patients with "chronic Lyme disease"

BACKGROUND

There is no evidence of current or previous Borrelia burgdorferi infection in most patients evaluated at university-based Lyme disease referral centers. Instead, psychological factors likely exacerbate the persistent diffuse symptoms or "Chronic Multisymptom Illness" (CMI) incorrectly ascribed to an ongoing chronic infection with B. burgdorferi. The objective of this study was to assess the medical and psychiatric status of such patients and compare these findings to those from patients without CMI.

METHODS

There were 240 consecutive patients who underwent medical evaluation and were screened for clinical disorders (eg, depression and anxiety) with diagnoses confirmed by structured clinical interviews at an academic Lyme disease referral center in New Jersey. Personality disorders, catastrophizing, and negative and positive affect also were evaluated, and all factors were compared between groups and with functional outcomes.

RESULTS

Of our sample, 60.4% had symptoms that could not be explained by current Lyme disease or another medical condition other than CMI. After adjusting for age and sex, clinical disorders were more common in CMI than in the comparison group (P <.001, odds ratio 3.54, 95% confidence interval, 1.97-6.55), but personality disorders were not significantly more common. CMI patients had higher negative affect, lower positive affect, and a greater tendency to catastrophize pain (P <.001) than did the comparison group. Except for personality disorders, all psychological factors were related to worse functioning. Our explanatory model based on these factors was confirmed.

CONCLUSIONS

Psychiatric comorbidity and other psychological factors are prominent in the presentation and outcome of some patients who inaccurately ascribe longstanding symptoms to "chronic Lyme disease."

Effects of external qigong therapy on osteoarthritis of the knee. A randomized controlled trial

The objective of our study was to assess the efficacy of external qigong therapy (EQT), a traditional Chinese medicine practice, in reducing pain and improving functionality of patients with knee osteoarthritis (OA). One hundred twelve adults with knee OA were randomized to EQT or sham treatment (control); 106 completed treatment and were analyzed. Two therapists performed EQT individually, five to six sessions in 3 weeks. The sham healer mimicked EQT for the same number of sessions and duration. Patients and examining physician were blinded. Primary outcomes were Western Ontario MacMaster (WOMAC) pain and function; other outcomes included McGill Pain Questionnaire, time to walk 15 m, and range of motion squatting. Results of patients treated by the two healers were analyzed separately. Both treatment groups reported significant reduction in WOMAC scores after intervention. Patients treated by healer 2 reported greater reduction in pain (mean improvement -25.7 +/- 6.6 vs. -13.1 +/- 3.0; p < 0.01) and more improvement in functionality (-28.1 +/- 9.7 vs. -13.2 +/- 3.4; p < 0.01) than those in sham control and reduction in negative mood but not in anxiety or depression. Patients treated by healer 1 experienced improvement similar to control. The results of therapy persisted at 3 months follow-up for all groups. Mixed-effect models confirmed these findings with controlling for possible confounders. EQT might have a role in the treatment of OA, but our data indicate that all EQT healers are not equivalent. The apparent efficacy of EQT appears to be dependent on some quality of the healer. Further study on a larger scale with multiple EQT healers is necessary to determine the role (if any) of EQT in the treatment of OA and to identify differences in EQT techniques.

Abatacept in children with juvenile idiopathic arthritis: a randomised, double-blind, placebo-controlled withdrawal trial

BACKGROUND

Some children with juvenile idiopathic arthritis either do not respond, or are intolerant to, treatment with disease-modifying antirheumatic drugs, including anti-tumour necrosis factor (TNF) drugs. We aimed to assess the safety and efficacy of abatacept, a selective T-cell costimulation modulator, in children with juvenile idiopathic arthritis who had failed previous treatments.

METHODS

We did a double-blind, randomised controlled withdrawal trial between February, 2004, and June, 2006. We enrolled 190 patients aged 6-17 years, from 45 centres, who had a history of active juvenile idiopathic arthritis; at least five active joints; and an inadequate response to, or intolerance to, at least one disease-modifying antirheumatic drug. All 190 patients were given 10 mg/kg of abatacept intravenously in the open-label period of 4 months. Of the 170 patients who completed this lead-in course, 47 did not respond to the treatment according to predefined American College of Rheumatology (ACR) paediatric criteria and were excluded. Of the patients who did respond to abatacept, 60 were randomly assigned to receive 10 mg/kg of abatacept at 28-day intervals for 6 months, or until a flare of the arthritis, and 62 were randomly assigned to receive placebo at the same dose and timing. The primary endpoint was time to flare of arthritis. Flare was defined as worsening of 30% or more in at least three of six core variables, with at least 30% improvement in no more than one variable. We analysed all patients who were treated as per protocol. This trial is registered, number NCT00095173.

FINDINGS

Flares of arthritis occurred in 33 of 62 (53%) patients who were given placebo and 12 of 60 (20%) abatacept patients during the double-blind treatment (p=0.0003). Median time to flare of arthritis was 6 months for patients given placebo (insufficient events to calculate IQR); insufficient events had occurred in the abatacept group for median time to flare to be assessed (p=0.0002). The risk of flare in patients who continued abatacept was less than a third of that for controls during that double-blind period (hazard ratio 0.31, 95% CI 0.16-0.95). During the double-blind period, the frequency of adverse events did not differ in the two treatment groups. Adverse events were recorded in 37 abatacept recipients (62%) and 34 (55%) placebo recipients (p=0.47); only two serious adverse events were reported, both in controls (p=0.50).

INTERPRETATION

Selective modulation of T-cell costimulation with abatacept is a rational alternative treatment for children with juvenile idiopathic arthritis.

FUNDING

Bristol-Myers Squibb.

The relationship between affect balance style and clinical outcomes in fibromyalgia

OBJECTIVE

Affective balance, relative levels of negative affect (NA) and positive affect (PA), better describes emotional functioning than NA or PA alone. Affect balance styles and their relationship to clinical outcomes were compared between patients with fibromyalgia (FM) and controls.

METHODS

FM patients (n = 79) were compared with patients with other medical conditions (controls; n = 92). Patients underwent a physical examination, completed questionnaires, and were screened for clinical disorders such as depression, with diagnoses confirmed by structured interview. Affect balance style categories were calculated as follows: healthy (high PA/low NA), low (low PA/low NA), reactive (high PA/high NA), and depressive (low PA/high NA).

RESULTS

Compared with controls, FM patients had lower levels of PA (P = 0.0031; P values are adjusted for multiple testing), higher levels of NA (P = 0.0061), lower levels of functioning (P < 0.0001), and more clinical disorders (P = 0.0031). Groups differed regarding affect balance style (P = 0.0061), with FM patients being more likely than controls to be categorized as depressive (odds ratio 5.60) and reactive (odds ratio 3.81). FM patients and controls with reactive and depressive affect balance styles reported poorer functioning (P < 0.0001) compared with patients with healthy affect balance style. Finally, there was an association between affect balance style and psychiatric comorbidity (P < 0.0001), with patients with depressive and reactive affect balance styles having a 9.00 and 4.75 odds ratio, respectively, of having psychiatric comorbidity compared with patients with healthy affect balance style.

CONCLUSION

Depressive (low PA, high NA) and reactive (high PA, high NA) affect balance styles were predominant in FM patients and related to poor functioning and psychiatric comorbidity.

Basic science for the clinician 45: CD4+ T-cell subsets of probable clinical consequence

I have often said "blessed be the splitters, for they shall inherit the earth." By that I mean that it is only by studying carefully culled populations, approaching, but never quite reaching, homogeneity that we can ever gain real insights into rheumatologic diseases. Differentiating tuberculous from gouty from rheumatoid arthritis was a good start, and when Moll and Wright identified the seronegative spondyloarthropathies, we were on our way to establishing "splitters" as leaders. Predictably, once T cells were identified as different from B cells, the floodgates opened. Subsets galore were described, with more isolated populations in the T-cell family, but we are now finding heterogeneity in B-cell populations, as well, which has been discussed in a previous article in this series. But as for T cells... well, it has not been smooth sailing. I initially trained in a laboratory that was firmly committed to the proposition that there were within the CD8 population not only cytotoxic cells but also "suppressor cells." Problem is, no one could ever isolate the little buggers, and so the idea of a suppressor or regulatory subpopulation of CD8+ T cells went the way of the Edsel. As noted in a previous article in this series, T regulatory cells were finally identified but not within the CD8+ population. And there are other regulatory subsets within both CD4+ and CD8+ T-cells populations and even new effector and memory populations that can be identified by their surface markers and functions. It is high time to review some of them; some of these populations may be involved in the immunopathogenesis of our diseases and undoubtedly will shortly be targets of immunotherapeutics. Although previous articles in this series discussed some of these subsets, I thought expanding on what is known about another recently described subset and putting them all together in one review might be helpful.

Basic science for the clinician 43: the mitogen-activated protein kinase family in inflammatory signaling

Growth factors, cytokines, chemokines, apoptotic stimuli, TLR ligands, stress-a lot can happen to a cell in day-to-day living, but these are extracellular phenomena, and all influence the inner workings of the cell. Once the ligand binds to the receptor, or the stress, occurs, changes occur within the cell that eventuate in intranuclear transcription of new genes, subsequent changes in cellular structure and function, and often in the release of chemicals that transmit signals to self (autocrine) and other cells (paracrine and juxtacrine). Often, these changes occur due to the activation of cascades of kinases, a perireceptor choreography that is only now being elucidated. The human "kinome" (the various families of kinases) is very complex; we will limit ourselves in this discussion to the mitogen-activated protein kinases.

Basic Science for the Clinician 44

There has been a sea change in our understanding of atherosclerosis. We have come a long way from the days where eating too much fat and not getting enough exercise and having the wrong genetic background was thought to be the entire story. A few years ago, the cardiologists began to embrace inflammation as a possible pathogenetic mechanism and from that came high-sensitivity C-reactive protein testing for just about everyone. Chronic systemic inflammation became an area of interest. We have learned that it is more than just corticosteroid use that causes accelerated atherosclerosis in our rheumatoid and lupus patients. Even C-reactive protein may be a pathogenetic player, not only a diagnostic clue. Oxidized phospholipids and the cells that recognize them may be crucial in the evolution of the atherosclerotic plaque. Statins may be useful in suppressing inflammation, not only in suppressing cholesterol levels. And now even cardiologists are thinking about immune mechanisms! A strange world, but the beneficiaries of going through this looking glass will be our patients. A true understanding of this seems to have required a most circuitous route-sometimes you have to leave for a long journey before you can return and really see home for the first time.

Basic science for the clinician 42: handling the corpses: apoptosis, necrosis, nucleosomes and (quite possibly) the immunopathogenesis of SLE

Death happens. It is, in essence, part of life. Humans deal with death in a variety of different ways, but often by keeping it at arms' length. At the cellular level, there are many forms of death, part of the development of organs and tissues (apoptosis) and part of pathologic processes (necrosis). The former, as has been described in an earlier paper in this series, is designed to eliminate the corpse with no evidence that it was ever there. Clearance is usually swift and effective, avoiding inflammation and specific immune interventions or responses. However, there is gathering evidence that autoimmunity leading to systemic lupus erythematosus may be due to ineffective or improper clearance of apoptotic debris, making it proinflammatory and allowing it to become highly immunogenic. This formulation also suggests therapeutic options that have already been demonstrated effective in controlling models of human autoimmune disease. This article reviews some aspects of this theory and some of the molecular biologic features of necrosis, apoptosis, and other forms of cell death.

A Pilot Study of the Efficacy of Heart Rate Variability (HRV) Biofeedback in Patients with Fibromyalgia

Fibromyalgia (FM) is a non-inflammatory rheumatologic disorder characterized by musculoskeletal pain, fatigue, depression, cognitive dysfunction and sleep disturbance. Research suggests that autonomic dysfunction may account for some of the symptomatology of FM. An open label trial of biofeedback training was conducted to manipulate suboptimal heart rate variability (HRV), a key marker of autonomic dysfunction.

METHODS

Twelve women ages 18-60 with FM completed 10 weekly sessions of HRV biofeedback. They were taught to breathe at their resonant frequency (RF) and asked to practice twice daily. At sessions 1, 10 and 3-month follow-up, physiological and questionnaire data were collected.

RESULTS

There were clinically significant decreases in depression and pain and improvement in functioning from Session 1 to a 3-month follow-up. For depression, the improvement occurred by Session 10. HRV and blood pressure variability (BPV) increased during biofeedback tasks. HRV increased from Sessions 1-10, while BPV decreased from Session 1 to the 3 month follow-up.

CONCLUSIONS

These data suggest that HRV biofeedback may be a useful treatment for FM, perhaps mediated by autonomic changes. While HRV effects were immediate, blood pressure, baroreflex, and therapeutic effects were delayed. This is consistent with data on the relationship among stress, HPA axis activity, and brain function.

Basic Science for the Clinician 41

We now have an emerging sense of the details of how cytokines deliver their signals through the specific receptors to which they bind and the means by which these messages are modulated. Using common mechanisms, many of which have been described in past articles in this series, tight controls are maintained over this signaling. A better understanding of the molecular details of these pathways has provided insights into the pathogenesis of some malignancies and immunodeficiency syndromes and may ultimately yield therapeutic agents of use in the treatment of inflammatory and autoimmune diseases.

Basic science for the clinician 31: CD molecules of relevance to immunity, inflammation, and rheumatologic syndromes

Molecular biologic technology has allowed us to study some of the many proteins expressed by leukocytes at different stages of differentiation, activation, and proliferation. Being able to purify cells with 1 or more surface molecules (eg, by FACS or lysis) with monoclonal antibodies and complement and identifying changes as cells are stimulated or activated has given us real insights into what is happening and how we might be able to modify cells that are going astray (eg, malignancy, autoimmunity). Over the years, there has been remarkable cooperation between laboratories to bring order out of chaos; by trading reagents, scientists have been able to identify the molecules being identified by different laboratories and come up with standardized names, often within the CD, or "clusters of differentiation," framework. These names are not acronyms, and the function and role of the molecule bearing a certain CD designation is not apparent. Worse, the proliferation of numbered CD molecules (over 250, with more to come after another conference in 2004) makes interpretation of the literature very difficult for those not immersed in the field. Thus, I have chosen (nearly arbitrarily and often based on my own interests) a number of CD molecules to briefly describe, pointing out the clinical relevance of each. It is worth reflecting on the fact that many of these were discussed in previous contributions to this series (as is pointed out in the following article). For those of you with the fortitude to follow this series, see how far you (and all of science) have come!

Molecular biology and immunology for clinicians 19: Protein purification and synthesis technology

Everywhere one looks in the practice of medicine there is the need to understand things at the level of specific proteins: vaccine design using a single protein would be much safer and efficient than the whole organism; diagnostic tests would be less prone to false-positive results if a single protein could be used; and on and on. The DNA revolution allowed us to manipulate the specific genes making proteins of interest, leading to the ability to make single proteins, called recombinant proteins, in inexhaustible supply. And now we can make chimeric proteins, like the mythical animal, with the head of one protein, the tail of another, and perhaps the body of a third--as many components as you like, the sky is the limit.

Molecular biology and immunology for clinicians 17: T-cell signal transduction

Peptide antigen recognition by T-cells occurs because of the interaction of the epitope cradled within the peptide-binding groove of the major histocompatibility complex molecule on the surface of an antigen-presenting cell with the T-cell antigen receptor, a heterodimer whose chains belong to the immunoglobulin superfamily. Passage of the message from the receptor to the cell's nucleus occurs via a complex choreography of kinases, calcium, and chemical combinations consisting of families of proteins described by arcane acronyms, numbers and letters that perplex the casual observer. However, taming the T-cell is crucial in transplantation and in controlling autoimmunity. Behind the jargon is a fascinating, albeit confusing, set of mechanisms that already offer therapeutic promise.

Molecular biology and immunology for clinicians 18: Heat shock proteins/chaperonins

Heat shock proteins are a highly conserved set of families of proteins produced after a variety of stresses, both pathologic and physiologic. They are made by all living cells; all cells use basically the same mechanisms to deal with profound stresses. The second remarkable feature of the heat shock proteins is that their sequence and structure are remarkably conserved across broad stretches of evolutionary history: from Escherichia coli to Homo sapiens, heat shock proteins have not changed a lot! Finally, as alluded to previously, heat shock proteins are involved in physiologic functions as well, such as keeping hormonal and antigen receptors and cell cycle-related proteins in their appropriate state of readiness or inactivity, awaiting the ligand that will activate them. Polypeptide chains emerge from the ribosome as a straight chain that then assumes a tertiary structure (e.g., alpha helices, beta-pleated sheets, disulfide and hydrogen bonds). The process of folding into this final structure may require help because the required tertiary structure may not be the one into which the polypeptide chain would fold if left to its own devices. Scaffolding may be needed to coax the polypeptide to fold into its proper functional final structure, which may not be the morphology most thermodynamically favored. The polypeptide chain contains a series of potentially interactive surfaces (with other sections of the polypeptide or with other proteins in the cell), just as a receptor has at least one potentially interactive surface. Heat shock proteins guard these potentially interactive surfaces from unwanted interactions with extraneous and irrelevant "suitors" and may help coax the protein into the desired interaction. The alternative to this assistance may be that the protein folds into a useless blob or a shape that is not optimal for its intended use; such misfolded proteins are degraded by normal housekeeping functions of the cell. The highly conserved nature of heat shock proteins means that the immune response to heat shock proteins of pathogens or malignant cells may recognize and then react with host heat shock proteins and produce autoimmune disease.

Molecular biology and immunology for clinicians 15: Antigen presenting cells--class I

Class I-bearing antigen presenting cells (APCs) monitor intracellular proteins which are cellular proteins made on a routine basis, endogenous proteins made by stressed cells, proteins made by infected or transformed cells, or proteins made by intracellular pathogens, e.g., viruses, chlamydiae, mycoplasma, Listeria, and some Enterobacteriaceae. The mechanisms by which peptides interact with and are expressed by class I complexes on the surface of APCs is described and contrasted with the circumstances of class II antigen presentation.

Molecular biology and immunology for clinicians, 14: Antigen presenting cells--Class II

Pivotal to immunity and auto-immunity is the ability of the human immune response to make antigen-specific responses, both cellular and humoral. T- and B-cells contain within themselves the ability to recognize and react to specific antigens, but they must be made aware of the presence of their target in the surrounding environment to respond. Turns out this part of the education of T-cells (not B-cells, which are activated by specific antigens in a different manner) is provided by a large number of cells, all coming under the umbrella term: antigen-presenting cells. Understanding how these cells take up molecules from the environment or acquire protein molecules from the intracellular milieu, manipulate them, and then offer the modified material to engage potentially responding cells in an immunological educational conversation is crucial to understanding normal immune function and, of course, auto-immunity and other forms of immune dysregulation. In the broadest of terms, there are two sources of proteins: endogenous (produced within the cell) and exogenous (produced outside of the cell), and there are two not entirely mutually exclusive pathways involved in antigen processing and presentation. To decrease confusion between these two separate pathways antigens, I will proceed with a description of the latter in this paper and cover the former in the next paper in this series. So, now on to antigen processing and presentation of proteins.

Basic Science for the Clinician 40

mRNA is made from DNA. Protein is made from mRNA. Although one might say that "DNA is forever," the same cannot be said for mRNA or protein. These molecules are made in response to the cell's present needs; once the cell's circumstances change, a whole new repertoire of proteins may be needed and the previous set of proteins may be unnecessary, perhaps even deleterious. So, the cell must be able to eliminate the characters in the previous act in favor of the actors needed for the current act. In addition, there is good evidence that the DNA to mRNA to protein flow may not be efficient; abnormal proteins, as well as damaged or misfolded proteins, are quite common and must also be eliminated. This process depends on the ability of the cell to tag the protein to be eliminated with a small protein (or chain of these proteins) that targets the protein to a special structure for digestion into its constituent amino acids for recycling into new proteins. This very common protein tag was identified in the 1970s and called "ubiquitin"--it truly was everyplace! In addition, ubiquitin is crucial to targeting normal proteins to their appropriate place in or on the cell and for recycling of proteins. Ubiqutination of proteins and what follows this tagging are crucial to the normal function of cells. The complexity of these processes is being used for therapy in oncology now and perhaps in immunology and rheumatology in the near future.

Basic Science for the Clinician 39

Were there to be a crossroads through which all inflammatory signaling passed, controlling that junction would provide the ultimate therapeutic target for rheumatoid arthritis and many, if not all, autoimmune diseases. It now seems likely that no single cytokine or cytokine family represents such a crucial nexus. However, there is reason to believe that there may be an intracellular bottleneck that does: the family of NF-kappaB proteins. This family of proteins allows cytokine-receptor signals to enter the nucleus and either enhance or suppress the transcription of many genes involved in inflammation and in cellular survival itself. The same set of proteins is also involved in apoptosis and likely in carcinogenesis. The delicate choreography of control systems, balancing the effects of NF-kappaB proteins on the multiple DNA sites that are targeted, is also a prime target for specific therapies. Moreover, the NF-kappaB system interdigitates with other intracellular systems, eg, kinases, ubiquitin-associated protein degradation, that are critical to the normal function of cells, involved in homeostasis and inflammation, in autoimmune diseases and malignancy.