By T. Anktos. Wayne State University.
Check the spelling generic ciprofloxacin 1000 mg line, imagine the sound of the word and make a guess at the resistance a word is likely to oppose: easy to learn or not? Four- syllable words such as perseverance will demand more time than monosyllabics such as and best 250 mg ciprofloxacin, or buy ciprofloxacin 500 mg with amex, and but cheap ciprofloxacin 250 mg without prescription. Go through the list a second and third time, either line by line or leaping at random from word to word. Push the words around in your mind, squeeze them, press them, and stretch them. Finally, test yourself by covering first the right column and then the left column. As thrilling as 100 percent results are, the first learning session is only the starting point for a weeklong consolidation process. Remember the forgetting curve of the Memory chapter. After one day, the percentage of correct answers is dramatically down, and after one month, recall may be 20 percent or less. As learning is nothing and recalling is everything, the second pillar of word nailing is repetition. Find out which strategy fits you best, either daily repetitions or repetitions on day 1, 3, 6, 10, 17, and 31, or any other regime. You will soon notice that after every re- exposure, memory traces are easier to reactivate. Determine that every single word has safely arrived in lifelong memory. Very young children ask their family for help, and a grandmother might interrogate her grandson, ‘Young boy, please tell me what açúcar means. Revisiting the word lists frequently and marking ‘difficult’ words for further revision is one such system. Alternatively, you can use index cards or word trainers on electrical devices. At a rate of 20, 30, or 40 new words a day, the time will come when you will feel like a force-fed French goose. The prevention: nail words five days a week and stop nailing at weekends. If saturation develops nonetheless, pause for an entire week. Good language manuals usually present around 2,000 words – that is far short of your final word score of 5–15,000. This is a miserable situation, because you are too good to continue working with manuals, but not good enough for reading essays, newspapers or novels. At this early stage, not even dictionaries are helpful – deciphering a text where half of the words are unknown is achingly slow. There is one acceptable solution: nailing carefully selected word compilations that are grouped by topic and divided into basic and advanced vocabulary. Good compilations present around 7,000 words and offer free pronunciation audio files (see www. Define the number of pages you will nail every day and start ploughing your way through them. People who have never used these books sometimes observe that learning hundreds of pages of words out of context is not an exciting perspective. I agree, but the alternative – looking up 10,000 words in a dictionary – is not sexier. Anticipate at least two rounds and possibly another round after 6 to 12 months. To your satisfaction, you will realise that daily listening to your audio sources (remember the manual CDs, TV programmes and audio books of the Listening chapter) has paved the way to understanding grammar. In fact, humans have an innate ability to grasp grammar, and this ability doesn’t disappear with adult age. Don’t be afraid of the technical terms of grammar, the nouns, pronouns, adverbs, tenses, modes, etc. Think of the parts that you know from your car – gearbox, headlights, battery, brakes, suspension, chassis, radiator, dipstick, cylinder, driveshaft, exhaust pipe, jack, lug nuts, spark plug, hubcap, etc. In comparison, becoming familiar with a handful of grammar terms is a bagatelle. Working through compilations of frequent words is like working on an assembly line.
But the immune response to many viruses includes robust antibody and CTLattack (Knipe and Howley 2001) buy cheap ciprofloxacin 500mg online. As more parasite genomes are sequenced cheap ciprofloxacin 500mg overnight delivery, it may be useful to look at which potential antigenic sites do in fact show signiﬁcant variation cheap ciprofloxacin 500mg visa. Those highly variable sites can be studied to determine if they are CTL or antibody epitopes buy ciprofloxacin 500mg visa, providing clues about which type of immunity imposes the strongest selective pressure on the parasite. Parasite Escape within Hosts 7 Speciﬁc immunity favors parasites that change their epitopes and escape recognition. In this chapter, I summarize examples of parasite escape and the consequences for antigenic diversity within hosts. The ﬁrst section presents HIV and hepatitis C virus (HCV) as two pathogens that evolve within hosts to escape speciﬁc immunity. HIV variants escape recognition by CTLs, whereas HCV variants escape rec- ognition by speciﬁc antibodies. HIV also diversiﬁes its surface molecules in order to attack diﬀerent cell types. Changing tissue tropisms over the course of an infection provide an additional force to drive the evolu- tion of parasite diversiﬁcation within hosts. HIV and HCV are both RNA viruses, which mutate frequently and evolve rapidly. The importance of within-host immune escape by random mutations in DNA-encoded pathogens remains to be studied. The second section describes how parasites interfere with host immu- nity. For example, viruses may disrupt MHC presentation of antigens, send misleading signals to natural killer cells, block programmed cell death (apoptosis) of infected cells, orexpress cytokines that alter im- mune regulation. In some cases, parasite antigens may lack variation because the parasite repels immune attack by interfering with host im- munity rather than altering the speciﬁcity of its epitopes. The third sectionfocuseson parasites that escape host immunity by switching gene expression between variants stored within each genome. Asingleparasite expresses onlyoneofthevariants from the archival genomic library. Each parasite lineage changes expression from one stored gene to another at a low rate. As host immunity builds against acommon variant, one or more newly expressed variants can rise. The host must then build another speciﬁc immune response against the new variants. Parasites that switch variants in this way may gain by extending the total time of infection. Additionally, switching may help to avoid the immunological memory of a previously infected host. The fourth section introduces processes that enhance or retard the coexistence of antigenic variants within hosts. If antigenic variants com- pete for a common resource, such as host cells or a limiting nutrient, 94 CHAPTER 7 then one competitively dominant variant tends to drive the other vari- ants extinct. Resource specialization allows diﬀerent variants to coexist, for example, when each variant attacks a diﬀerent cell type. Spatial vari- ation in the density of resources can allow diﬀerent variants to dominate in diﬀerent compartments of the host’s body. The ﬁnal section takes up promising issues for future research. Natural selection favors variants that escape immune recognition, although escape is of- ten temporary. Selection may also favor diversiﬁcation of the pathogens for the ability to attack diﬀerent types of host cells. They compared the rate of nonsynonymous (dN) nucleotide replacements that cause an amino acid change versus the rate of synonymous (dS) nucleotide replacements that do not cause an amino acid change. A high dN/dS ratio suggests positive natural selection favoring amino acid change; a low dN/dS ratio suggests nega- tive natural selection opposing change in amino acids (Page and Holmes 1998; see chapter 15 below). The nonsynonymous substitutions in these epitopes typically abolished recognition by a matching CTL clone. The population of viruses accu- mulated diversity in the dominant epitopes over the course of infection within hosts. These results suggest that CTL attack based on speciﬁc recognition drives the rapid rate of amino acid replacements in these epitopes. The early viruses infected macrophages, replicated slowly, and the viral particles were susceptible to antibody-mediated clearance. PARASITE ESCAPE WITHIN HOSTS 95 The late viruses infected T cells, replicated more than 1,000 times faster than early viruses, and were less sensitive to antibody-mediated clear- ance.
All comments and the authors’ proposed actions were reviewed by representatives of the participating organizations of the Drug Effectiveness Review Project before finalization of the report cheap ciprofloxacin 750mg free shipping. Names of peer reviewers for the Drug Effectiveness Review Project are listed at www buy ciprofloxacin 750mg low price. Public Comment This report was posted to the Drug Effectiveness Review Project website for public comment discount ciprofloxacin 500 mg amex. We received comments from 3 pharmaceutical companies: Boehringer Ingelheim Pharmaceuticals purchase ciprofloxacin 500mg online, Inc. RESULTS Overview For update 2, literature searches identified 1705 citations. We received dossiers from 1 pharmaceutical manufacturer, Eli Lilly and Company. By applying the eligibility and exclusion criteria to titles and abstracts of all identified citations, we obtained full-text copies of 245citations. After reapplying the criteria for inclusion, we ultimately included 39 publications, representing 29 unique studies. See Appendix D for a list of excluded studies and reasons for exclusion at this stage. Figure 1 shows the flow of study selection for Update 2. Appendix E details the results of literature searches for studies included previously. Newer antiplatelet agents 18 of 98 Final Update 2 Report Drug Effectiveness Review Project a Figure 1. Results of literature search for Update 2 1679 records identified from 26 additional records identified database searches after through other sources removal of duplicates 1705 records screened 1460 records excluded at abstract level 245 full-text articles assessed 206 full-text articles excluded for eligibility • 2 non-English language • 47 ineligible outcome • 85 ineligible intervention 39 publications included in • 9 ineligible population qualitative synthesis • 27 ineligible publication type • 13 trials (+7 companion • 17 ineligible study design publications) • 19 outdated or ineligible • 16 observational studies systematic review • 2 systematic reviews • 1 other* *Pooled analysis of trials a 19 A modified PRISMA diagram was used. For adults with acute coronary syndromes or coronary revascularization via stenting or bypass grafting, prior ischemic stroke or transient ischemic attack, or symptomatic peripheral vascular disease do antiplatelet agents differ in effectiveness? Summary of Findings Direct evidence • No head-to-head trials of newer antiplatelet agents for acute coronary syndrome managed medically only or peripheral vascular disease were identified. Newer antiplatelet agents 19 of 98 Final Update 2 Report Drug Effectiveness Review Project Acute coronary syndrome managed with coronary revascularization via stenting or bypass grafting The TRITON-TIMI 38 trial provided moderate- to high-strength evidence that prasugrel is similar to clopidogrel for reduction of all-cause mortality and cardiovascular mortality at 15 months when used post percutaneous coronary intervention. It also provided high- strength evidence that prasugrel reduces the risk of target-vessel revascularization at 15 months. There was also low-strength evidence that the difference between ticlopidine and clopidogrel in cardiovascular mortality was not significant at 30 days. Stroke or transient ischemic attack The PRoFESS trial provided high-strength evidence that extended-release dipyridamole plus aspirin failed to demonstrate noninferiority when compared with clopidogrel for the primary outcome of recurrent stroke and that there was no significant difference between extended-release dipyridamole plus aspirin and clopidogrel on the secondary outcomes of all-cause mortality and cardiovascular mortality. Indirect evidence Acute coronary syndrome managed medically There was moderate-strength evidence from CURE of no significant difference between clopidogrel plus aspirin compared with aspirin alone in reduction of all-cause mortality at 12 months, but there was a significantly greater reduction in myocardial infarction with clopidogrel plus aspirin. Stroke or transient ischemic attack Indirect evidence from aspirin-controlled trials of newer antiplatelet agents was consistent with direct evidence from head-to-head trials in suggesting no significant differences in effectiveness between extended-release dipyridamole plus aspirin and clopidogrel or between clopidogrel and ticlopidine. However, this result should be considered inconclusive as the FASTER trial was likely underpowered to detect a significant treatment difference. Newer antiplatelet agents 20 of 98 Final Update 2 Report Drug Effectiveness Review Project Peripheral vascular disease In the peripheral arterial disease subgroup of the CAPRIE study, there was no significant difference between clopidogrel and aspirin in cardiovascular mortality. All-cause mortality and revascularization data were not reported separately for the peripheral arterial disease subgroup. Detailed Assessment Acute coronary syndrome managed medically Direct evidence No direct evidence was identified. Indirect evidence 20, 21 The Clopidogrel in Unstable Angina to Prevent Recurrent Ischemic Events Trial (CURE) was a randomized, double blind, placebo-controlled trial of good quality that evaluated the early and long-term efficacy and safety of clopidogrel and aspirin. The trial included 12 562 patients hospitalized within 24 hours of the onset of chest pain, with a diagnosis of acute coronary syndrome, and without ST-segment elevation. Initial inclusion criteria allowed for patients > 60 years of age who had a history of coronary artery disease but no acute electrocardiogram changes. After the first 3000 patients were enrolled, only patients with myocardial necrosis or electrocardiogram changes (higher risk patients) were included in the study. The patients were randomized to clopidogrel (300 mg loading dose, 75 mg daily thereafter) plus aspirin or placebo 22 plus aspirin for a mean of 9 months. The primary outcome was a composite endpoint of death from cardiovascular causes, nonfatal myocardial infarction, or stroke (clopidogrel: 9. The benefit of clopidogrel was observed 21 within 24 hours after randomization in the primary outcome. In CURE, clopidogrel/aspirin was compared with placebo/aspirin and there was no significant difference in cardiovascular deaths (5. The incidence of myocardial infarction for clopidogrel/aspirin compared with placebo/aspirin at 12 months was 5. These component outcomes were all secondary endpoints and the study was not powered to detect a difference. Newer antiplatelet agents 21 of 98 Final Update 2 Report Drug Effectiveness Review Project The Clopidogrel for High Atherothrombotic Risk and Ischemic Stabilization, 13 Management, and Avoidance (CHARISMA) trial was another randomized, double-blind, placebo-controlled trial of good quality.
Across the 2 studies buy cheap ciprofloxacin 750mg on-line, somnolence and fatigue were the most common adverse events in the clonidine groups discount 500mg ciprofloxacin otc, and there was some evidence that the rate of adverse events peaked at 2 weeks in the clonidine groups best ciprofloxacin 500 mg. Guanfacine XR Adverse events were reported more frequently with guanfacine XR discount 250 mg ciprofloxacin with visa, in a dose-dependent manner, 160, 161, 163 in 2 of 3 studies compared with placebo. The rate of adverse events in drug groups ranged from 74% with fixed dosing (1 to 4 mg daily) to 88. Discontinuations due to adverse events were also more frequent in a dose-dependent manner with extended-release guanfacine. The rates for 2, 3, and 4 mg daily were: 3%, 9%, and 14% in 1 161 160 study and 10%, 15%, and 23% in the other compared with 8% and 1% with placebo respectively. Flexible dosing resulted in a 10% discontinuation rate due to adverse events. The most common individual adverse events reported in the guanfacine XR groups were somnolence, fatigue, and headache. Adolescents 170-179, 182, 242 Placebo-controlled trials of immediate-release methylphenidate provided limited evidence of short-term stimulant tolerability in adolescents. Immediate-release methylphenidate was associated with significant appetite and sleep disturbances across some, but not all placebo- 172, 173, 176, 179 controlled trials. Additionally, adolescents taking immediate-release methylphenidate frequently reported increases in dulled affect, social withdrawal, irritability, and 175, 179 stomachache in 2 placebo-controlled trials. Trials of other stimulants provide no long-term evidence on safety. One 17-day study comparing methylphenidate OROS and mixed amphetamine salts reported a single adverse event 180 – urinary difficulty – in a patient receiving methylphenidate OROS. Another multi-phase, Attention deficit hyperactivity disorder 78 of 200 Final Update 4 Report Drug Effectiveness Review Project placebo-controlled study of methylphenidate OROS reported no serious adverse events during the 2-week double-blind phase, although 1 serious adverse event (suicidal ideation) was reported during a run-in, open-label dose titration phase. Other adverse events commonly reported during the open-label dose titration phase were headache (25% of patients), decreased appetite (21%), insomnia (15%), and abdominal pain (9%). However, adverse event rates during the double- blind phase were similar for methylphenidate OROS and for placebo and the only withdrawal 181 due to adverse events was reported in a placebo patient. Results from a 4-week trial found that when compared with placebo, mixed amphetamine salts XR was associated with higher rates of anorexia/decreased appetite (35. Five patients taking mixed amphetamine salts XR withdrew from the study due to adverse events. No placebo patients discontinued due to adverse events and no serious adverse events were reported in either group. In adolescents, lisdexamfetamine resulted in a higher rate of overall adverse events compared with placebo, with the highest rate associated with 70 mg daily (30 mg = 65%, 50 mg 184 = 69%, 70 mg = 72%, and placebo = 58%). Decreased appetite was the most frequent adverse event reported, at 34% for all lisdexamfetamine doses, compared with 2. Insomnia was reported by 11% with lisdexamfetamine and 4% with placebo, with the highest rate again being in the 70 mg daily group (14%). Weight decrease was reported in a clearly dose- dependent manner (30 mg = 4%, 50 mg = 9%, 70 mg = 15%, and placebo = 0). Adults Direct evidence Methylphenidate OROS compared with immediate-release methylphenidate Among 41 adults with good tolerability on immediate-release methylphenidate, the proportion with no adverse events dropped by 7% after switching to methylphenidate OROS. In contrast, the proportion with no adverse events increased by 25% among 12 adults who continued with immediate-release methylphenidate. The statistical significance of this difference is unclear, however, as analysis of the change was not presented and the study was limited by a small sample size and the presence of a between-groups imbalance at baseline in the proportion who 186 started out with no adverse effects. Immediate-release guanfacine compared with immediate-release dextroamphetamine The number of adverse events reported was similar in 17 adults after 2 weeks of once daily treatment with either immediate-release guanfacine 1. Muscle tension was the most common side effect with immediate-release dextroamphetamine (29%). Fatigue was the most common side effect with immediate-release guanfacine (23%). Withdrawals due to adverse events were not reported. Modafinil compared with immediate-release dextroamphetamine Modafinil and immediate-release dextroamphetamine were associated with similar rates of insomnia (38% compared with 19%, P=NS), muscle tension (24% compared with 19%; P=NS) 188 and appetite suppression (24% compared with 19%, P=NS). Attention deficit hyperactivity disorder 79 of 200 Final Update 4 Report Drug Effectiveness Review Project Indirect evidence Atomoxetine Adverse events were reported in all 8 placebo-controlled trials of atomoxetine of general samples 189-195 of adults with ADHD (Table 12). Withdrawals due to adverse events increased over time and were generally greater for atomoxetine than for placebo. Appetite disturbance was consistently significantly more common with atomoxetine than for placebo; whereas, the difference between atomoxetine and placebo was more variable with regard to insomnia. Adverse events in placebo-controlled trials of atomoxetine Author Year Treatment Withdrawals due to Appetite Sample size regimen adverse events disturbance Insomnia Spencer “Occurred “Did not occur 192 76 mg x 3 1998 4% vs. Immediate-release dextroamphetamine 198, 199 Some reporting of adverse events was available in both of 2 fair-quality trials.
For example discount ciprofloxacin 1000mg amex, if the hazard ratio for death for a treatment is 0 order ciprofloxacin 250 mg with mastercard. Head-to-head trial: A trial that directly compares one drug of a particular class or group to another in the same class or group cheap 1000 mg ciprofloxacin with visa. Heterogeneity: The variation in or diversity of participants cheap ciprofloxacin 250 mg free shipping, interventions, and measurement of outcomes across a set of studies. Indirect analysis: The practice of using data from trials comparing one drug in a particular class or group to a drug outside that class or group or to placebo and attempting to draw conclusions about the comparative effectiveness of drugs within a class or group based on those data. For Topical calcineurin inhibitors Page 66 of 74 Final Report Drug Effectiveness Review Project example, using direct comparisons between drugs A and B and between drugs B and C to make indirect comparisons between drugs A and C. Intention to treat (ITT): The use of data from a randomized controlled trial in which data from all randomized patients are accounted for in the final results. Trials often report results as being based on intention to treat despite some patients being excluded from the analysis. Internal validity: The extent to which the design and conduct of a study are likely to have prevented bias. Generally, the higher the interval validity, the better the quality of the published study. Inter-rater reliability: The degree of stability exhibited when a measurement is repeated under identical conditions by different raters. Intermediate outcome: An outcome not of direct practical importance but believed to reflect outcomes that are important. For example, blood pressure is not directly important to patients but it is often used as an outcome in clinical trials because it is a risk factor for stroke and myocardial infarction. Mean difference: A method used to combine measures on continuous scales (such as weight), where the mean, standard deviation, and sample size in each group are known. Meta-analysis: The use of statistical techniques in a systematic review to integrate the results of included studies. Although they are sometimes used interchangeably, meta-analyses are not synonymous with systematic reviews. However, systematic reviews often include meta-analyses. Meta-regression: A technique used to explore the relationship between study characteristics (for example, concealment of allocation, baseline risk factors, or timing of the intervention) and study results (for example, the magnitude of effect observed in each study) in a systematic review. Multivariate analysis: Measuring the impact of more than one variable at a time while analyzing a set of data. N of 1 trial: A randomized trial in an individual to determine the optimum treatment for that individual. Noninferiority trial: A trial designed to determine whether the effect of a new treatment is not worse than a standard treatment by more than a prespecified amount. Nonrandomized study: Any study estimating the effectiveness of an intervention (harm or benefit) that does not use randomization to allocate patients to comparison groups. There are Topical calcineurin inhibitors Page 67 of 74 Final Report Drug Effectiveness Review Project many types of nonrandomized studies, including cohort studies, case-control studies, and before -after studies. Null hypothesis: The statistical hypothesis that one variable (for example, which treatment a study participant was allocated to receive) has no association with another variable or set of variables. Number needed to treat (NNT): An estimate of how many people need to receive a treatment before one person would experience a beneficial outcome. Observational study: A type of nonrandomized study in which the investigators do not intervene, instead simply observing the course of events. Odds ratio (OR): The ratio of the odds of an event in one group to the odds of an event in another group. One-tailed test: A hypothesis test in which the values for which we can reject the null hypothesis are located entirely in one tail of the probability distribution. For example, testing whether one treatment is better than another (rather than testing whether one treatment is either better or worse than another). Open-label trial: A clinical trial in which the investigator and participant are aware which intervention is being used for which participant (that is, a trial that is not blinded). Random allocation may or may not be used in open-label trials. Per protocol: The subset of participants from a randomized controlled trial who complied with the protocol sufficiently to ensure that their data would be likely to exhibit the effect of treatment. Per protocol analyses are sometimes misidentified in published trials as intention-to- treat analyses. Point estimate: The results (for example, mean, weighted mean difference, odds ratio, risk ratio, or risk difference) obtained in a sample (a study or a meta-analysis) that are used as the best estimate of what is true for the relevant population from which the sample is taken. Pooling: The practice of combining data from several studies to draw conclusions about treatment effects. Power: The probability that a trial will detect statistically significant differences among intervention effects. Studies with small sample sizes can frequently be insufficiently powered to detect difference. Precision: The likelihood of random errors in the results of a study, meta-analysis, or measurement.
The constant region is sometimes referred to as the Fc fragment discount 750 mg ciprofloxacin otc, and the variable region as the Fab fragment proven 1000 mg ciprofloxacin. Redrawn from Janeway (1993) cheap 250 mg ciprofloxacin with amex, with permission from Roberto Osti 500mg ciprofloxacin with amex. Recombination creates a large number of diﬀerent antibodies. Upon infection a few of these rare types may match a parasite epitope, stimulating ampliﬁcation of the B cell clones. The matching B cells increase their mutation rate, cre- ating many slightly diﬀerent antibodies that vary in their aﬃnity to the 18 CHAPTER 2 Antigen Antigen binds to a Mutations cause specific antibody small variations in on a B cell. Tighter binding causes faster replication of the cellular clone. Mutational diversity Recombinational diversity Figure 2. Recombinational mechanisms produce a wide va- riety of diﬀerent antibody molecules (ﬁg. All B cells of a particular clone are derived from a single ancestral cell that underwent recombination. Mem- bers of a clone express only a single antibody type. Cells are stimulated to divide rapidly when an epitope matches the antibody receptor. This creates a large population of B cells that can bind the epitope. These cells undergo in- creased mutation in their antibody gene during cell division, producing a set of antibodies that vary slightly in their binding properties. Stronger binding causes more rapid cellular reproduction. This aﬃnity maturation enhances the antibody-epitope ﬁt. Those mutant cells that bind more tightly are stimu- lated to divide more rapidly. This evolutionary ﬁne-tuning of the B cell population is called aﬃnity maturation. Naive B cells produce IgM immunoglobulins before stimulation and aﬃnity maturation. After aﬃnity maturation, B cells produce various types of immunoglobulins by changing the constant region (ﬁg. The most common are IgG in the circulatory system and IgA on mucosal surfaces. On ﬁrst encounter with a novel parasite, the rare, matching antibodies cannot control infection. While the host increases production of match- ing antibodies, the infection spreads. Eventually the host may produce suﬃcient antibody to clear parasites that carry the matching epitope. If VERTEBRATE IMMUNITY 19 the parasites, in turn, vary the matched epitope, the host must expand new antibody types to clear the variant parasites. Once the host expands an antibody speciﬁcity againstamatching epi- tope, it maintains a memory of that epitope. Upon later exposure to the same epitope, the host can quickly produce large numbers of matching antibodies. This memory allows the host toclearsubsequent reinfection without noticeable symptoms. Antibodies typically bind to surface epitopes of parasites. Thus, an- tibodies aid clearance of parasites circulating in the blood or otherwise exposed to direct attack. Once an intracellular parasite enters a host cell, the host must use other defenses such as T cells. The host’s major histocompatibility complex (MHC) molecules bind these short peptides within the cell. The cell then transports the bound peptide-MHC pair to the cell surface for presentation to roving T cells. Each T cell recep- tor can bind only to particular peptide-MHC combinations presented on the surface of cells. The TCR variability is generated by a process similar to the recombinational mechanisms that produce antibody diversity in B cells. However, T cells do not go through aﬃnity maturation, so once the recombination pro- cess sets the TCR for a T cell lineage, the TCR does not change much for that lineage.