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.

Basic science for the clinician 38: B cells, factories, and immunomodulators

In a previous article in this series, we explored how developing pre-T cells learn how to be well-behaved T cells that recognize and honor the "self versus nonself" dichotomy of the universe. B cells do much of the same sort of thing, with multipotent stem cells becoming committed to ultimately becoming B cells within the bone marrow and then, after judicious culling of the flock, going off to the spleen to learn the final lessons needed to become "well-behaved" B cells. Like with T cells, there are a large number of things that can, and do, go wrong. If there is a failure of the system and B cells do not develop properly, hypogammaglobulinemia may develop as a result of a number of immune deficiency syndromes that can be quite devastating. If autoreactive cells survive to emerge into the periphery, autoimmunity, either organ-specific or more global, may occur. If B cells in the periphery proliferate in an uncontrolled fashion, a variety of B cell lymphoproliferative syndromes may develop, recognizable by the phenotypic markers of their originating B cell lineage level of differentiation. The full details of how autoreactive B cells survive and thrive, only to cause disease, are not yet clear, but identification of many of the phenotypic surface markers and circulating growth factors identified to this point have borne therapeutic fruit.

Basic science for the clinician 37: Protecting against autoimmunity-tolerance: mechanisms of negative selection in the thymus

As noted in previous articles in this series, tolerance, the ability of the immune system to differentiate self from nonself and leave the former alone, is a vital characteristic of a successful (and safe) immune system. With the detection of the molecule called aire (autoimmune regulator), the mechanism whereby autoreactive thymocytes encounter extrathymic proteins within the thymus and therefore are deleted, is now far better understood; aire was the subject of a prior article in this series. The absence of aire leads to autoimmune polyendocrinopathy, proof that aire is the center of an amazing "filtering" system. However, there are other mechanisms at work. Irregularities in expression of other proteins such as hypoxia-induced factor-1 (HIF-1) and CTLA4, have been implicated in autoimmune disease, the former in rheumatoid arthritis, the latter in autoimmune thyroid disease and lupus. Defects in intracellular factors involved in transcription of key apoptotic proteins have also been implicated in the escape of autoreactive thymocytes from the thymus, leading to autoimmune and lymphoproliferative syndromes as well. Changes in the proteins that oversee acetylation of histone lead to differential patterns of gene expression. At least 2 proteins involved in this process, HDAC and nur77, have been implicated in changes in survival of thymocytes. Yet again, there are multiple layers at work in the immune system; I have no idea how many more will be brought to light, which are phylogenetically most ancient or which will prove the most clinically relevant. For now, it is enough to bask in our new-found knowledge and know that the time from laboratory oddity, to animal model development, to therapeutic and/or diagnostic applications grows shorter each year since the molecular biologic revolution.

Basic science for the clinician 35: CD1, invariant NKT (iNKT) Cells, and gammadelta T-cells

As noted in previous articles in this series, the very heterogeneous MHC class I and II molecules present peptide antigens to T-cells. However, there is another family of less heterogeneous MHC-related molecules. CD1 molecules present lipid antigens, oftentimes to 2 other distinct families of T-cells: gammadelta T-cells (named because they bear a T-cell antigen receptor consisting of a gamma chain and a delta chain rather than the alpha chain/beta chain heterodimer on most T-cells) and iNKT cells (T-cells that bear markers previously defined on natural killer cells). CD1 molecules and the gammadelta T-cells and iNKT cells to which they present antigens have fundamental responsibilities for immune surveillance over intracellular pathogens and serve other roles that place them at the boundary between innate and acquired immunity. The gammadelta T-cell has been implicated in the pathogenesis of many diseases, rheumatologic and otherwise, suggesting that better understanding of these cells, and of CD1 molecules, may help us explain the immunopathogenesis of some inflammatory diseases and how to craft more targeted therapies in many fields of medicine.

Reactive arthritis

ReA consists of sterile axial or peripheral articular inflammation,enthesitis, and extra-articular manifestations. Most patients are HLA-B27 positive, although determining the B27 status of an individual patient is irrelevant. Exposure to specific bacterial antigens is usually the inciting factor. Diagnosis usually can be made by clinical examination and history. The current standard therapy is NSAIDs and physiotherapy, but molecular biologic treatment may ultimately become the mainstay in recalcitrant and severe ReA.

Basic science for the clinician 30: The immunologic synapse

Interactions between discrete and independent cells, immune or otherwise, present a variety of potential problems. How do you make sure the cells can communicate effectively? How do you preclude neighboring cells from "listening in on a conversation" that may be meant only for one set of "ears"? How can you sharpen the hearing of those ears so they will be capable of detecting small signals but not get distracted by random noise in the system? How can you selectively enhance the sense of hearing in times of great need or urgency and then diminish the "gain" of the system when it is not immediately required? How can you assure that the call will be terminated at the end of the conversation? Passage of communication molecules and/or interaction of cell surface markers require close and stable apposition of the cell delivering the message with the receiving cell. In the nervous system, these problems were successfully addressed in the nerve-nerve or nerve-myocyte (neuromuscular junction) synapses. Not surprisingly, given the parsimony of nature, the immune system uses some of the same design features, even some of the same molecules, to achieve an effective communication strategy. The term "immunologic synapse" was coined only 2 decades ago, but the structure it describes has become a very hot topic in immunology and cell biology. The immunologic synapse allows the activation of a unique T cell, with an antigen receptor recognizing its antigen in the grasp of the antigen-presenting cell's (APC's) major histocompatibility complex (MHC). A better understanding of this transient immune cell-cell interactive structure allows one to weave the functions of T cell antigen receptors, lipid rafts, adaptor molecules, and nuclear signaling molecules together into one cohesive, flowing communication supersystem. Appreciation of the intricacies of the synapse also identifies targets that one day may be used to interfere with antigen-specific immune responses, eg, autoimmunity.

Basic science for the clinician 26: Tolerance--mechanisms and manifestations

Usually the immune system monitors our internal milieu, protecting us from external and internal risks, silently watching over the rest. Pathologic autoimmunity is usually avoided, except in certain animal models and certain immunogenetically predisposed people. On the other hand, "salutary autoimmunity" occurs in the interaction of immune systems with themselves or other immune pathways as part of control or recognition mechanisms, eg, idiotype network, epitope-MHC complex binding with B- or T-cell antigen receptors. There are means by which dangerous autoimmune reactants are eliminated from the repertoire before birth; some of these are described here. However, potentially dangerous autoimmune effectors can be identified in the immunologic repertoire of certain adult animal strains but not damage the animal; these latent autoimmune effector pathways are held in check in adult animals/humans by active suppressive mechanisms.The identification and control of autoimmunity may well be the holy grail of rheumatology. Autoimmunity may also be an active participant in a number of other organ systems and diseases, so lessons learned in immunology may apply broadly throughout medicine. Once a better understanding of the normal processes and aberrancies that lead to disease are had, one can look forward to interventions to reestablish tolerance, perhaps by something as simple as a capsule containing the appropriate self antigen-containing molecules--"oral tolerizing" as a cure for autoimmune diseases! There is much promising evidence in favor of the efficacy of oral tolerance in animal models, but as of yet, human disease has proven a harder nut to crack. Although the concept of oral tolerance is nearing its centennial, there is still much to learn!

Basic science for the clinician 36: protecting against autoimmunity: tolerance and aire, the immunologic shadow, and other mechanisms of negative selection in the thymus

One of the miracles of immunology is tolerance, the ability of the immune system to differentiate self from nonself and leave the former alone. Autoreactive thymocytes (the cells that would otherwise differentiate into mature autoaggressive T cells) are deleted from the emerging immunologic repertoire within the thymus; only a very small proportion of thymocytes survive the thymus--perhaps 2% to 5% emerge to become mature T cells in the periphery, the rest dying to assure tolerance. This apparent wastage somehow works to the benefit of the developing animal and if the process works, all goes well for the maturing immune system. In some autoimmune syndromes, autoreactive thymocytes are not eliminated within the thymus by either clonal deletion or activation-induced cell death; these then emerge to wreak their havoc. However, how does this deletion happen? Recent research from a number of groups has (incredibly!) identified expression of nonthymic, nonlymphoid proteins within the thymus (casting of the "immunologic shadow of self"), and this is under the control of a single protein: AIRE (autoimmune regulator). By allowing autoreactive thymocytes to encounter a broad spectrum of proteins from extrathymic organs, aire allows deletion of these cells and the maintenance of tolerance. The absence of aire leads to autoimmune polyendocrinopathy, proof that aire is the center of an amazing "filtering" system. These and other molecular mechanisms underlying tolerance are explored in this and the next paper in this series.

Basic science for the clinician 32: T-cells with regulatory function

Tolerance is one of the major requirements of a successful immune system: destroy invaders but recognize self and the benign environment to leave them alone. Central tolerance is achieved by deletion of T-cells with T-cell antigen receptors that recognize self-antigens too well. However, within the population of T-cells that actually survive the harrowing experience of passage through the thymus (wherein over 98% of all pre-T-cells perish), there persist T-cells capable of inducing autoimmune damage. How then to avoid autoaggression? One theory in the 1970s was that there were peripheral T-suppressor cells that actively dampened these autoimmune proclivities. One problem presented itself, however; despite the fact that such an immunologic activity could be measured, no one could identify the cells that mediated the activity and so the concept fell into disfavor. However, the concept of peripheral regulation by a distinct (at last identifiable!) population of T-cells is now back in vogue. These T-regulatory (T-reg) cells have an important function in immune homeostasis. T-reg demand our attention as we try to manipulate the molecular biology of immune responses and inflammation to control autoimmune disorders and enhance transplantation efficiency.

Lyme arthritis synovial gammadelta T cells instruct dendritic cells via fas ligand

gammadelta T cells participate in the innate immune response to a variety of infectious microorganisms. They also link to the adaptive immune response through their induction of maturation of dendritic cells (DC) during the early phase of an immune response when the frequency of Ag-specific T cells is very low. We observe that in the presence of Borrelia burgdorferi, synovial Vdelta1 T cells from Lyme arthritis synovial fluid potently induce maturation of DC, including production of IL-12, and increased surface expression of CD40 and CD86. The activated DC are then able to stimulate the Vdelta1 T cells to up-regulate CD25. Both of these processes are initiated primarily by Fas stimulation rather than CD40 activation of DC via high expression of Fas ligand by the Vdelta1 T cells. DC are resistant to Fas-induced death due to expression of high levels of the Fas inhibitor c-FLIP. This effect serves to divert Fas-mediated signals from the caspase cascade to the ERK MAPK and NF-kappaB pathways. The findings affirm the importance of the interaction of certain T cell populations with DC during the early phases of the innate immune response. They also underscore the view that as levels of c-FLIP increase, Fas signaling can be diverted from induction of apoptosis to pathways leading to cell effector function.

Basic Science for the Clinician 27

Ancient protective mechanisms are in place, deep within our defenses against infection and malignancy, often unappreciated until homologous proteins found within less phylogenetically advanced organisms are identified. Such is the case with 2 major recent finds, the Toll-like receptors (TLRs) and nucleotide oligomerization domain (NOD) families of innate immunity molecules. These families of receptors have high specificity, limited heterogeneity, and no plasticity; nonetheless, they play a pivotal role in rapid initial defenses against pathogens. Moreover, studies of the mechanisms of TLRs and NODs show how they and IL-1 and IL-18 stand at the threshold of the adaptive immune response and help to accelerate specific immune responsivity. Nonspecific reactivity of these preprogrammed receptors may be how relatively nonpathogenic organisms like yersinia and chlamydia may drive the inflammation of reactive arthritis and atherosclerosis. The inflammation of rheumatoid arthritis may be magnified, if not initiated, by these innate mechanisms as well.

Herbal Medications Commonly Used in the Practice of Rheumatology: Mechanisms of Action, Efficacy, and Side Effects

OBJECTIVE

To review the literature on herbal preparations commonly utilized in the treatment of rheumatic indications.

METHODS

Search of MEDLINE (PubMed) was performed using both the scientific and the common names of herbs. Relevant articles in English were collected from PubMed and reviewed.

RESULTS

This review summarizes the efficacy and toxicities of herbal remedies used in complementary and alternative medical (CAM) therapies for rheumatologic conditions, by elucidating the immune pathways through which these preparations have antiinflammatory and/or immunomodulatory activity and providing a scientific basis for their efficacy. Gammalinolenic acid suppresses inflammation by acting as a competitive inhibitor of prostaglandin E2 and leukotrienes (LTs) and by reducing the auto-induction of interleukin1alpha (IL-1alpha)-induced pro-IL-1beta gene expression. It appears to be efficacious in rheumatoid arthritis (RA) but not for Sjogrens disease. The antiinflammatory actions of Harpagophytum procumbens is due to its action on eicosanoid biosynthesis and it may have a role in treating low back pain. While in vitro experiments with Tanacetum parthenium found inhibition of the expression of intercellular adhesion molecule-1, tumor necrosis factor alpha (TNF-alpha), interferon-gamma, IkappaB kinase, and a decrease in T-cell adhesion, to date human studies have not proven it useful in the treatment of RA. Current experience with Tripterygium wilfordii Hook F, Uncaria tomentosa, finds them to be efficacious in the treatment of RA, while Urtica diocia and willow bark extract are effective for osteoarthritis. T. wilfordii Hook F extract inhibits the production of cytokines and other mediators from mononuclear phagocytes by blocking the up-regulation of a number of proinflammatory genes, including TNF-alpha, cyclooxygenase 2 (COX-2), interferon-gamma, IL-2, prostaglandin, and iNOS. Uncaria tomentosa and Urtica diocia both decrease the production of TNF-alpha. At present there are no human studies on Ocimum spp. in rheumatic diseases. The fixed oil appears to have antihistaminic, antiserotonin, and antiprostaglandin activity. Zingiber officinale inhibits TNF-alpha, prostaglandin, and leukotriene synthesis and at present has limited efficacy in the treatment of osteoarthritis.

CONCLUSIONS

Investigation of the mechanism and potential uses of CAM therapies is still in its infancy and many studies done to date are scientifically flawed. Further systematic and scientific inquiry into this topic is necessary to validate or refute the clinical claims made for CAM therapies. An understanding of the mechanism of action of CAM therapies allows physicians to counsel effectively on their proper and improper use, prevent adverse drug-drug interactions, and anticipate or appreciate toxicities.

RELEVANCE

The use of CAM therapies is widespread among patients, including those with rheumatic diseases. Herbal medications are often utilized with little to no physician guidance or knowledge. An appreciation of this information will help physicians to counsel patients concerning the utility and toxicities of CAM therapies. An understanding and elucidation of the mechanisms by which CAM therapies may be efficacious can be instrumental in discovering new molecular targets in the treatment of diseases.

Basic Science for the Clinician 34

As you saw in the first part of this description of interleukins, normal orchestration of wound healing, the protective immune response and inflammation involves many cells that must effectively communicate with each other. The means of this communication is often soluble messengers (cytokine) and many of them bear the title interleukin. 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 disease, eg, rheumatoid arthritis, osteoarthritis. I dealt with interleukins (IL) 3 to 16 in the first part of this project. We now pick up the story with IL-17. Turns out, much of the most exciting recent work in rheumatology has focused on IL-17 and IL-18. The disparate effects of the interleukins may be confusing, often a single cytokine producing multiple effects seemingly at crossed purposes, but we are in our infancy when it comes to insights into the molecular biology of normal immune function, homeostasis, inflammation, and disease.

Basic Science for the Clinician 28

The immune response is finely tuned to the various invaders that may cause damage and disease. There is an innate immune system and an acquired immune response, but there is much overlap and recruitment across these lines of demarcation. Broadly speaking, there are cellular immune responses (cellular effectors that identify intracellular pathogens and damage and kill the affected cell) and humoral (B cells become plasma cells which make antibodies to bind extracellular pathogens and their products) that draw upon both systems. At the pivotal point, where decisions are made whether to mount a primarily cellular or a humoral response are T-helper cells (CD4). As you may have read, CD4 cells come in at least 2 subtypes: TH1 cells predispose to the development of a primarily cellular responses and TH2 predispose to humoral responses. Not very complicated, but worthy of some discussion to look at the cytokines produced, the changes these cytokines evince, and how the balances (dare I say yin and yang) keep us healthy but also may get us into trouble!

Molecular Biology and Immunology for Clinicians 29

The development of an antigen-specific immune response depends on the peptide-loaded MHC molecule on the surface of the antigen-presenting cell being found by the antigen-specific receptor on the cell about to be activated (the T-cell antigen receptor for T-cells or the membrane-bound immunoglobulin molecule on B-cells). The details of this process are becoming clear now with the appreciation of the supramolecular organization of the structures that make this cell-cell interaction. In the last 6 years has come an appreciation of the heterogeneity of the lipid bilayer membrane (a concept first put forth over 20 years ago), with certain lipids and membrane-bound proteins segregating into discrete ships called "lipid rafts" sailing in the surrounding more liquid lipid bilayer membrane. Knowledge of these microscopic structures leads to a better understanding of how antigen-specific responses are triggered and how aberrant responses are avoided; as one leader in the field put it, "keeping T-cells rested but ready."Membrane heterogeneity directly contributes to the rapid development of a more formalized cell-cell interaction that has been termed the "immunologic synapse." It is at this synapse that the acquired immune response, antigen specificity, is learned. In addition to antigen presentation, lipid rafts have also been implicated in signaling through a large number of receptors, endocytosis, cell interactions with pathogens and toxins, budding of viruses from host cell membrane, and the pathogenesis of prion disorders. Yet again, an insight in one discrete field of cell biology is proving to be of great relevance in a host of other areas of study.

Molecular Biology and Immunology for Clinicians 25

The adaptive immune response specializes in reacting efficiently and rapidly with protein antigens. Many pathogens and host cells are coated with carbohydrates (more about lipid antigens and the response thereto in a future installment of this series). The carbohydrate arrays on pathogens are remarkable for their relative lack of diversity, remarkable conservation, and how different they are from the carbohydrates found on mammalian cells. Thus, they represent excellent targets for the innate immune response, which is characterized by limited effector molecule heterogeneity. Defense collagens are a class of innate immune response recognition proteins targeting these common carbohydrate motifs, a class you may not have encountered previously. These invariant germ-line encoded proteins are not produced as a specific response to a particular antigen. Nonetheless, they too have an antigen-binding site, called the carbohydrate recognition domain with the other end of the molecule (made up of collagen-like domains) devoted to the transmission of biologically relevant information, analogous with the antibody molecule's Fc component, but this is where the similarities end. Defense collagens have been broadly viewed as an "anti-antibody," broadly similar in structure and function. Despite the fact that they are germline-encoded and do not have individual antigen specificity, their phylogenetic longevity and durability prove the value of defense collagens in maintaining the host. On the basis of emerging studies, they may play important roles in the defense against many pathogens and in the pathogenesis of rheumatologic and other diseases. Thus, they are good targets for studies to better understand our diseases and to craft therapeutic manipulations in the future.

Molecular Biology and Immunology for Clinicians 24*

The human immune system consists of layer upon layer of response, communication, and coordination mechanisms added during its evolution throughout the last half billion years. Given the parsimony of nature, it is not surprising that many of the systems prominent within the human immune response are recognizable within the immune systems of less advanced species. Insights drawn from these species and common sense suggest that "autoimmune" reactivity was not the original or primary reason for the evolution of these mechanisms. Also, it becomes clear that certain functions thought to be "immune" may actually be nonspecific, really innate functions served by these ancient mechanisms. There is good evidence of communication between levels of the immune system, the innate and adaptive systems working with each other, often the former (not antigen-specific) preceding and serving to trigger or magnify the latter (antigen-specific). A future article in this series will focus more on the innate system and how it interdigitates with the adaptive system.

Molecular Biology and Immunology for Clinicians 23

The parsimony of nature can be stated as "if its not broke don't fix it, just tweak it and reuse it again and again." Nature recycles: once a motif is demonstrably useful it shows up again, often in unexpected places. Tumor necrosis factor and its receptor(s) are examples of this. At least 20 molecules have now been identified as being 25% homologous or more identical with tumor necrosis factor and being involved in a variety of immune and nonimmune functions. Members of the receptor superfamily have shared structural motifs and trigger shared intracellular signaling pathways. Rather than having been implicated in arcane and rare syndromes, some of these activities are pivotal in immune function and, when perturbed, some predispose to known immunodeficiency and autoimmune disease. Not surprisingly, some of these are becoming targets for immunomodulation. New members of these 2 superfamilies are currently being described and the newcomers and the "original stock" will show up in the clinic before you know it! Part of the confusion has always been that each laboratory describing a new biologic principle names the mediating compound. Thus, multiple labs, multiple names for the same protein (recall Ro/SS-A, La/SS-B). Thus, special attention is paid below to acronyms and their synonyms.

High expression of Fas ligand by synovial fluid-derived gamma delta T cells in Lyme arthritis

Gamma delta T cells accumulate at epithelial barriers and at sites of inflammation in various infectious and autoimmune diseases, yet little is understood about the function of tissue-infiltrating gamma delta T cells. We observe that gamma delta T cells of the V delta 1 subset accumulate in synovial fluid of human Lyme arthritis and are intensely cytolytic toward a wide array of target cells. Particularly striking is that the cytolytic activity is highly prolonged, lasting for at least 3 wk after stimulation of the gamma delta T cells with Borrelia burgdorferi. Cytolysis is largely Fas dependent and results from very high and prolonged expression of surface Fas ligand, which is transcriptionally regulated. This also manifests in a substantial level of self-induced apoptosis of the gamma delta T cells. In this capacity, certain gamma delta T cell subsets may serve as cytolytic sentinels at sites of inflammation, and perhaps at epithelial barriers.

Molecular Biology and Immunology for Clinicians 22

Natural killer (NK) cells (called "third population cells" many years ago because they did not bear surface markers of the first two defined populations, B cells and T cells) are now known to occupy a pivotal position in the immune system, straddling the "divide" between the innate and adaptive responses. Natural killer cells are capable of production of many cytokines, both pro- and anti-inflammatory, and induction of target cell death by lysis and/or programmed cell death (apoptosis). Some of these cytokines are pivotal in the autoimmune and antipathogenic immune responses, implicating NK cells in the pathogenesis of many human diseases. Multiple detection systems allow tight control of the potent effector systems that mediate NK cells' effects. Recent studies have shown that NK cell function is under tight control, with complex inhibitory and activating signaling assuring that these cells can accurately detect intracellular infection and malignant degeneration without damaging healthy cells. Although NK cell receptors do not have antigenic specificity, they do detect certain patterns on the surface of target cells. Their ability to make many cytokines that alter antigen-specific immune responses mediated by other cells puts NK cells in a unique position to influence both innate and adaptive responses.

Molecular Biology and Immunology for Clinicians 21

The human (mammalian) immune response includes two interrelated but separable components: the innate immune system and an adaptive immune response. The former constitutes the sole immune defense strategy of invertebrates. It is only with vertebrate evolution that an adaptive immune response, first cellular, then later humoral, develops. Recent studies and a reconsideration of the innate system allow a fuller appreciation of its complexities, unique qualities, and irreplaceable value. In the early days of an infection, long before an effective adaptive immune response can be mounted, the innate system puts up an effective defense. Innate systems provide the costimulatory signal needed to unleash the adaptive immune response. Future contributions to this series will provide details about some of the specific innate immune systems. This article serves as an introduction to this underappreciated (until recently) aspect of human immune defenses.

Molecular Biology and Immunology for Clinicians 20

If we accept the perfectly reasonable premise that the mass of inflammatory tissue in rheumatoid arthritis (and psoriatic arthritis or any other inflammatory joint disease) requires oxygen and nutrition to survive and grow, we are confronted with a novel concept for therapy: if we can block the nutritional supply of the pannus, we can suppress or prevent its growth and the subsequent destruction of the joint. Thus, an understanding of how new blood vessels nourish the inflammatory mass could be pivotal in successfully treating our patients. Angiogenesis is the process whereby new blood vessels enter the site of inflammation or growing malignancy to supply the invading tissue. Many growth factors and local tissue conditions help to determine blood vessel growth, there being pro- and anti-angiogenetic influences. Thus, this is fertile ground for therapeutic molecular manipulations.